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By M. O. Lai

"Metal matrix composite (MMC) with composition of Al-4.Swt.%Cu reinforced by IOwt.%TiB2 or ISwt.%SiC particulate has been successfully fabricated using powder metallurgy technique. Disk, compression and beam specimens were prepared with (a) layered structure containing ductile Al-4.Swt.%Cu with brittle Al-4.Swt.%Cu/TiB2 or Al-4.Swt.%Cu/SiC layers, and (b) homogenous constituent with composition of Al-4.Swt.%Cu/lOwt.%TiB2' The specimens for the fracture toughness measurement were built through three ductile-brittle-ductile alternating layers. For the beam specimens, the layers were built through brittle-ductile-brittle sequence. The brittle layer consisted of Al-4.S%Cu with fixed amount of reinforcement. Fracture toughness testing revealed an increase for layered composites although the total amount of the reinforcement was the same for all disk specimens. The increase in fracture toughness is due to the existence of ductile layers which manifests a strong influence on delaying the occurrence of fracture. It acts as a barrier to resist the propagation of crack and hence increases the fracture toughness of the layered MMC specimens, Delamination in the beam specimens was observed to be due to shear stresses. Fracture surfaces of both disk, compress and beam specimens were characterized using the SEM. IntroductionMechanical and thermal properties can be achieved by the incorporation of refractory secondary phases to constrain the plastic flow of the matrix in a metal matrix composite (MMC). The size of the reinforcement particulate incorporated must be in the range larger than the dislocation cell size and strongly bonded to the matrix (I). Particulate reinforced metal matrix composites hence provide high modulus, improved wear resistance and strength (2-4). Because of the incorporation of refractory phases which are generally brittle, the major limitation in the mechanical properties of MMCs is their limited ductility in comparison to their base metals. Cracks normally initiate from the reinforcement and voids (4, 5). Due to the lack of ductility, cracks propagate rapidly with increase in load. As a result, the interactions between reinforcement particles and propagating cracks have recently been of great research interest (6). In addition, volume fraction of reinforcement and aging condition of the matrix significantly affect the mechanical behaviour of MMCs. In the case of AI-3.5%Cu reinforced with varying volume fractions of SiC particulate, it has been found that the probability of particle fracture increased with increasing volume fraction of reinforcement (7)."

Jan 1, 1996

By Erwin L. Zodrow

"IntroductionThrough an extensive coal sampling project in the Sydney coalfield of Nova Scotia during 1981 - 1984 involving a majority of the mineable coals (Zodrow, 1985, Fig. 1), a sizeable inventory on trace, minor and major metals was established. In this paper, results of studying the inventory are summarized, concentrating mainly on the relationship that exists between metal variations and thickness of coal channel samples (i.e. trends) and on explaining the trends in geochemical and sedimentological terms. As an over-all conclusion the Everglades peat of Florida is proposed as a modern-day analogue to Upper Carboniferous peat swamp development that took place in the Sydney Basin.Data InventoryFor this study 17 channel samples were cut , 8 cm to 14 cm channel width and 8 cm to 10 cm depth, from 10 successive coals which in stratigraphically descending order are as follows: Point Aconi (3), overrider Lloyd Cove (2), Lloyd Cove (2), Stubbart (2), Harbour (4), Backpit (I), Phalen (,I), Shoemaker (1) and McAulay (I), where bracketed values signify the number of channel samples cut from a seam (Zodrow, 1985, Fig. I). Each channel sample was subdivided by 15 em incremental length yielding a total sample size of 137 for analysis. By appropriate modern techniques these samples were analyzed to determine concentration levels for 32 chemical elements and ash content, the average results of which are presented in Table 1.Tests were also made for Pd, Pt, Ga, Nb, Cd, Cs, Sm and W but their concentration levels in many instances hovered on the lower detection limits that were used and on this accounts are excluded from discussion. Ashing, when necessary for the determination of concentration levels, was done for 12 hours at a temperature not exceeding 450°C. Concentration levels for the elements are reported in reference to whole-coal or whole-coal equivalents and discussed on this basis. In the course of the analyses, lower detection limits received careful attention."

Jan 1, 1986

By M. Bevis, A. F. Acton, P. C. Rowlands

Defor~nation twinning and transformation twinning modes most likely to be operative in Fe-Ni and Fe-Ni-C martensites have been determined using a new theory of the crystallography of deformation t~inning.~ This analysis shows that potentially important conventional and nonconventional twinning modes1 have been omitted in previous analyses. Discussion is given on the relevance of the predicted twinning modes to the lattice invariant shear associated with the martensite transformation in steels and to anomalous deformation twinning in Fe-Ni-C martensites. THE two most important criteria which appear to govern operative twinning modes in metallic structures1 are that the magnitude of the twinning shear should be small and that the twinning shear should restore the lattice or a multiple lattice in a twin orientation. The latter criterion ensures that the shuffle mechanism required to restore the structure in a twin orientation is simple. These criteria have been adhered to in the prediction of twinning modes2"6 in bcc and bct single-lattice structures with axial ratios in the range y = 1 to 1.09 as, for example, encountered in martensite occurring in steels. Refs. 2 and 3 in particular consider the martensite transformation in steels and the twinning modes in these cases relate to transformation twinning, and hence the lattice invariant shear associated with the martensite transformation. The list of twinning modes which can be compiled from these sources is incomplete and the ranges of magnitude of shear considered could be unrealistically small, particularly in the case of deformation twinning. The latter consideration is supported by the fact that twinning modes with magnitudes of shear large compared with the smallest shear consistent with a simple shuffle mechanism have been established in, for example, the single-lattice structure mercury7 and the multiple-lattice structure zirconium.&apos; In addition the anomalous deformation twins reported by Ftichrnan4 to occur in a range of Fe-Ni-C martensites still remain unexplained. It is clear that a comprehensive analysis of twinning modes likely to be operative in martensite In steels is required. The results of the application of a new theory of the crystallography of deformation twinningg to these structures are presented in this paper. The theory has been used to determine all shears which restore the lattice or a multiple lattice in a new orientation with magnitude of shear up to a required maximum. The orientation relationships between parent and twinned lattices are not restricted to the classical orientation relationships of reflection in the twin plane or a rotation of 180 deg about the shear direction. PREDICTED TWINNING MODES Twinning modes which restore all or one half of lattice points to their correct twin positions will be referred to as m = 1 and m = 2 modes, respectively. These modes are the most likely to describe operative modes in single lattice structures. The bcc m = 1 and m = 2 modes which have magnitudes of shear s in the range s < 2 and s < 1, respectively, have been given10 and are reproduced here in Tables I and 11. Detailed discussion of the crystallography of these modes and cubic modes in general will be discussed elsewhere (~evis and rocker, to be published). The four twinning elements Kl, &,ql,7)2 as well as the magnitude of shear s are given for each twinning mode, and the twinning modes are given in order of increasing shear. Two twinning modes are given in each row of the tables, the twinning mode Kl, Kz, ql, q2 and the reciprocal twinning mode with elements Kl = K,, Ki = Kl, q: = q2, and 17; = ql. The m = 1 and m = 2 twinning modes which describe twinning shears with small magnitudes of shear and simple shuffle mechanisms in bct crystals with -y = 1 to 1.09 are given in Tables I11 and IV, respectively. On increasing the symmetry of the tetragonal lattice to cubic, that is making y = 1, all modes listed in Tables 111 and IV must reduce to crystallographically equivalent variants of the modes given in Tables I and 11, respectively, or become twinning modes with both shear planes as symmetry planes in the cubic lattice and hence not considered in Tables I and 11. With the exception of this last type of mode only those tetragonal twinning modes which reduce to modes 1.1, 1.2, 2.1, and 2.2 of Tables I and I1 are considered in Tables 111 and IV. For values of y in the range -y = 1 to 1.09 the tetragonal modes and the corresponding cubic twinning modes have approximately the same magnitude of shear. The twinning modes listed in Tables 111 and IV are therefore by the criteria given above the most

Jan 1, 1969

A bearing isolator is a noncontact, nonwearing, permanent bearing protection device. It has a rotor and a stator, and the two are unitized, so that they do not separate from one another while in use. The rotor turns with a rotating shaft, while the stator is pressed into a bearing housing. The two components interact to keep contamination out of the bearing enclosure and the lubricant in. Bearing isolators do not require lubrication or any particular shaft finish or condition. The best bearing isolators are made of metal, usually bronze. They use a vapor-blocking feature that inhibits the free transfer of vapor contamination when the rotating equipment is cycled on and off.

Jan 1, 2004

By Elmars Ence, Harold Margolin

The partial isothermal section of the Ti-Cu-Zr system at 750°C has been studied. The crystal structure of Ti2Cu has been detevnlined as tetragonal and when expressed as face-centered tetragonal, a = 4.164, c = 3.611 A, and c/a = 0.867. TITANIUM systems in which ß-titanium decomposes eutectoidally into a and a compound rather readily are known as active eutectoid systems. Recently in active eutectoid alloys based on the Ti-Cu system, and containing additionally A1 and Zr, it has been found that zirconium may produce both moderate weakening and marked strengthening at elevated temperatures.&apos; In order to obtain some insight into the behavior of zirconium, an attempt was made to determine whether compounds of the type Tix Zr and TixZryCu exist. Only results of the Ti-Zr-Cu studies are reported here since data on Ti-Zr alloys will be presented in a separate publication. EXPERIMENTAL PROCEDURE Alloys were nonconsumably arc melted in argon atmosphere as 15-g buttons, prepared from materials of the following purities: Bureau of Mines electrolytic Ti — Bhn 63 OFHC copper Reactor Grade Zirconium Bhn .C 150 Prior to alloy preparation the electrolytic titanium was premelted to avoid excessive spattering of the charges during melting. The weight losses during melting did not exceed 1 pct of the total weight of the charge. The alloys prepared are listed in Table I together with analyzed compositions. in cases where they were determined. Specimens for heat treatment were wrapped in molybdenum sheet, annealed in argon-filled quartz capsules, and quenched by breaking the capsules under iced brine. About 1 to 2 sec are required to remove the capsule from the furnace, drop it into the iced brine and break it. Because of the insulation effect of the quartz, this delay in quenching should not produce a large drop in temperature. In many instances, no difference or little difference has been detected between the same specimen quartz capsule quenched or directly quenched in vacuum by an impinging stream of water.&apos; Ti-Cu-Zr alloys were homogenized for 48 hr at 825°C prior to annealing at 750°C. Annealing for 5 days at 750°C produced the same results as 11 days at temperature and it was therefore assumed that 5 days was sufficient to establish equilibrium. Titanium-copper alloys were homogenized for 40 hr at 900°C prior to heat treatment for 6 days at 750°C. Specimens for metallographic examination were electropolished and etched with the following solution:

Jan 1, 1962

By Edward Hanrahan

September 1981 I&apos;m here today to report on a revolution -- a revolution in the way the Federal Government looks at energy. I&apos;m not talking about a simple change in the relative emphasis on sources -- such as more recognition for coal and nuclear power, with less rhetoric about "soft- technology." Nor am I describing a mere change in focus -- from the demand side to the supply side. And I am not referring exclusively to our obvious goal of budget cuts. No, I&apos;m here to discuss a fundamental change in Federal direction -- one that started as soon as President Reagan was inaugurated, and one that is articulated in the National Energy Policy Plan he sent to Congress in July. That brief policy document was backed up by three volumes of supporting data; but I think I can catch it&apos;s flavor for you in just three phrases: * First, various energy forms complete with each other and complement one another. * Second, fair competition among them (which includes honest pricing) will give us the best "energy mix." • And, finally there may be ligitimate arguments about where Federal responsibility in regard to energy spills over into Federal interference; but it&apos;s about time we drew the distinction -- and eliminated the latter. This Administration&apos;s national energy policy is quite different from any we have had in recent years. It is tuned to human nature and changing times. We are seeking the best practical solutions in the energy -a lot better than the ones we have been offered before, but still something less than perfection. One way we do that is by counting on a fully informed public to guide it&apos;s own destiny. And, instead of treating energy as an isolated entity, we recognize it as part of the overall economy. The President&apos;s Program for Economic Recovery is as much a factor in energy policy as the specific actions of the Department of Energy. One striking difference from the past energy policy 1s that this policy plan does not say: "In 1985 we will -produce so many hundreds of millions of tons of coal: . . . or . . . "By the end of this century the Nation will be deriving X percent of it&apos;s electricity from wind generators." Unfortunately, targets like these are what many people have come to expect from the Federal Government -- and what they think of as energy policy, whether the figures hold up in the long run or not. But . . . think about it! Nether the Department of Energy nor any other part of the Federal Government produces coal, or mines uranium, or manufactures solar collectors. There are only a few sections of the country where the Federal Government generates and sells electricity. So it does not take any great insight to recognize that the amount of energy we will produce or consume as a Nation In the future depends on many factors beyond direct government action. And those future totals cannot be predicted precisely, anyway -- by the Government or by anybody else. According to our way of thinking, the choices should be up to the people. When the free market works within a healthy economy, individuals express their preferences in the marketplace -- adjusting the balance of all energy factors continually in a way that no computer could be programmed to reflect perfectly. So, instead of having the Government issue a rigid set of numerical goals, our main concern simply is that there be enough energy. We want the Nation itself to decide how much that should be, what form it should take, and how that energy should reach consumers. The marketplace decides. Considering the recent past, this is indeed a revolutionary idea. It has some pitfalls, and we won&apos;t reach this ideal of free choice overnight. But that is where we are headed. And I&apos;ll offer some evidence in a few minutes that the policy has already started working. First, let me give you some of it&apos;s highlights: 1) Nobody who appreciates the philosophical underpinnings of this Administration will be surprised that the energy policy shows faith In domestic energy production and the supply side of the economy; but it also recognizes the important role of energy conservation -- the wise and efficient use of energy resources.

Jan 1, 1982

According to published reports, controlled production from the Masjid-i-Sulaiman and Haft Kel fields for the year 1934 was as follows: No new development of major importance in either of these areas is reported. Owing to the increasing- demand in North Iran, particularly for gasoline and kerosene, it has been arranged that this market shall in future draw its supplies from a newly constructed refinery at Kennan-shah. This refinery is connected by a 3-in. pipe line, 145 miles long, with the Naft-i-Shah field, on the borders of Iraq and Iran. The crude oil will pass through a topping plant at the field and the products will be stored and pumped to the Kermanshah refinery in such proportions and quantities as are demanded by actual market requirements.

Jan 1, 1935

By K. Hambrice, E. Fauveau

"When it comes to measuring the level of bulk solids, liquids, and everything in between, guided-wave radar technology now offers more level-detection capabilities than ever before. For an ever-widening range of previously hard-tomeasure products such as molten sulphur, liquid ammonia and petrochemicals, guided-wave radar transmitters provide accurate level measurements even under harsh chemical environments, wide variations in operating temperatures and pressures, and low dielectric constants.Great strides have been achieved in making these units easier to configure to a variety of process applications coupled with the simplicity of integrating these devices with most digital communication protocols. These improvements come as welcome relief to process engineers within an expanded range of level applications across several different industries that seek solutions to measuring the contents of tanks, silos, hoppers, bins, mixing basins, and vessels.Because radar transmitters have no moving parts, radar has already established a dominant niche in level measuring that quickly distances itself from mechanical means, which do not hold up as well in dirty service. Radar achieves its nonmechanical level detection capability by measuring the time of flight of the transmitted signal.Known more accurately as time domain reflectometry (TDR), the process involves sending microwave energy down into a vessel. When the pulse of radar energy reaches the product (indicated by a change in impedance), part of the pulse is reflected back toward the transmitter.A receiver measures the exact duration of time between the transmitted and reflected signal — the “time of flight.” The device analyzes this time and ultimately displays the level of the product as a distance in feet, metres, or other engineering units."

Jan 1, 2003

By David A. Hedderly-Smith

Sealaska Corporation, the Alaska Native Regional Corporation of Southeastern Alaska, was organized under the laws of the state of Alaska pursuant to the federal Alaska Native Claims Settlement Act of 1971. Large areas of Sealaska&apos;s 630,000-acre (250,000 hectare [ha]) fee subsurface holdings are underlain by carbonate, and while much of this material is assumed to be common variety limestone and lesser dolomite, at least two areas in the Silurian Heceta Limestone contain high-quality limestone at tidewater. This limestone has many potential commercial uses. On northern Prince of Wales Island, about 90 miles (144 km) north-northwest of Ketchikan, resource development at Sealaska&apos;s Calder deposit has established a reserve of 13 mil- lion short tons (st) (12 million metric tonnes [mt]) of carbon- ate rock containing an average of greater than 98 percent CaC03, approximately 0.5 percent MgO, less than 0.5 per- cent Si02, and approximately 0.15 percent Fe203, with insolubles averaging less than 0.5 percent and an average Hunter Brightness of 92.07 for the -150 mesh grind (with a bright- ness cutoff of 90). The deposit is open at depth and to the south. Ultimate reserves will likely be several times those currently established. In 1998, Sealaska began mining the Calder deposit, with about 100,000 st (90,000 mt) produced, and also completed a marine terminal one half-mile (800 m) from the deposit. The terminal can load ships up to 680 feet (200 m) in length at a rate of 2,000 st (1,800 mt) per hour. 0 m) in length at a rate of 2,000 st (1,800 mt) per hour. On Dall Island at Breezy Bay, about 60 miles (100 km) southwest of Ketchikan, Sealaska has identified a limestone reserve in excess of 150 million st (135 million mt) that (based on 18 surface samples distributed evenly over about a section of land) contains about 98 percent CaC03, and less than 0.5 percent MgO, 0.5 percent Si02, and 0.15 percent Fe203. Brightness of the Breezy Bay carbonate is considerably less than at Calder. Five samples of brighter material from Breezy Bay returned brightness analyses in the high 80s and low 90s; average brightness is probably below the mid- 80s. Sealaska has also identified a deposit containing more than 19 million st (17 million mt) of similar rock near View Cove, a few miles south of Breezy Bay.

Jan 1, 2001

By Chris A. Fleming, Daan Seymore

The Golden Jubilee Mine in South Africa is the first mine in the Western World to introduce resin-in­pulp technology for the recovery of gold from a cyanide-leached slurry. Located in the Eastern Transvaal region of the country, the plant processes approximately 375 metric tons• of ore per day, of which over 90 per cent is mined in an open pit adjacent to the metaflurgical plant, while the remaining 5 to 10 per cent is trucl<ed in from two small high-grade deposits, located about 10 kilometers from the plant. The gold grade in the open pit is about 1 git, while the values m the two high-grade deposits range between 5 and 15 git. At the current treatment rate, the proven reserves m the three locations will last about another 10 years. Early testwork indicated that the ore was not well suited to conventional filtration processing or to heap leaching because of its high cfay content, and that carbon-m-pulp (CIP) would probably prove to be the most viable metallurgical route. Tcstwork to establish the feasibility of CIP for this application was carried out at Mintek in 1985. This worl<, which was based on batch-leaching and carbon-loading tests, indicated that CIP was technically feasible, but that both the rate of gold loading and the gold-loading capacity of the carbon were inferior to those obtained with Witwatersrand ores. The poor adsorption characteristics of the carbon were attributed to the abnormally high concentration of natural organic compounds (humates and fulvates) in the ore. Batch tests were therefore also carried out with strong-base resins, since resins are known (1] to be far less susceptible to organic fouling than is activated carbon. The results were very promising, and pointed to fast kinetics and a high loading capacity. (Fig. 1 ). Notwithstanding these findings, it was decided to recover gold with activated carbon at Golden Jubilee Mine because the CIP process was, by then, well established in South Africa and elsewhere in the world, whereas resin-in-pulp (RIP) was unproven technology. The r>lant was commissioned in September 1986 and, for 18 months, operated in a carbon-in-leach (CIL) configuration, i.e. with a total of . six leach tanks, the last four of which contained activated carbon. As could have been predicted from the laboratory results, the performance of the CIL plant was generally poor, low gold loadings on the carbon (less than 1500 git) and high losses of soluble gold (0.2 to 0.3 p.p.m.) bemg characteristic of the operation. Consequently, it

Jan 1, 1990

By J. R. Long, T. R. Graham, R. S. Dean

ALTHOUGH considerable information has been published concerning manganese additions to the aluminum bronzes, these data refer principally to the two-phase alloys containing 8 to 11 pct aluminum, with some incidental information on the single-phase alpha solid solution alloys. Strauss1 gives an excellent review of the literature on aluminum bronzes up to 1927 and a bulletin2 of the Copper Development Association brings the bibliography up to 1938. The most extensive work on manganese addition is that of Rosenhain and Lantsberry,3 who investigated alloys ranging up to 10 pct aluminum and up to 10 pct manganese, and presented data on the physical properties of sand-cast, chill-cast, and several wrought alloys. The greater portion of the work, however, concerns alloys ranging from 7 to 10 pct aluminum in the cast condition and sheds little light on the properties of wrought single-phase alloys. Corson4 notes that alloys containing 10 pct manganese and 4 pct aluminum are not hardenable by heat-treatment, while one with 15 pct manganese and 5 pct aluminum can be hardened, but he gives no tensile data on it. In fact, no systematic study of the properties of single-phase wrought alloys containing substantial amounts of manganese has been reported. It should also be noted that most of the investigators worked with alloys containing significant amounts of iron and silicon, and that these impurities, whether intentionally added or accrued from the raw materials used in the preparation of the alloys, may be expected to have a direct bearing on the resultant properties. In the work on alloys made with electrolytic manganese, the Bureau of Mines has undertaken an investigation of the copper-manganese-aluminum system for the purpose of establishing the constitution and properties of high-purity alloys. In a recent paper5 the authors reported a metallographic investigation of the alpha solid solution area and the adjoining fields of the copper-manganese-aluminum system up to 50 pct manganese. This study established the alpha-phase boundaries at 50° temperature levels from 400° to 850°C. It was found that the addition of manganese to copper-aluminum alloys decreases the solubility of aluminum in the alpha phase (Fig I), curving the boundary toward the copper-manganese base line. The greatest change occurs in the first 20 to 25 pct manganese, which decreases the solubility of aluminum to approximately 4 pct. With larger amounts of manganese the alpha boundary tends to parallel the copper-manganese binary. At 1300°F and higher,

Jan 1, 1947

By C. Allen Born

There is a saying, the greater the gratitude, the shorter the speech. That puts me in a quandary, because while I am grateful for the honor you do me today, I also want to talk about a subject very important to all of us. A few months ago, when I was asked to submit a title for my talk, I chose "Quality where it counts." I did so because perhaps the most important thing we at Amax did in our restructuring was to commit to quality in all our businesses - quality people, assets, and operations. Together, they create quality performance, which produces quality growth and increased shareholder value - our prime corporate mission. We are dedicated to quality. At Amax, quality means everything. Today, I want to discuss quality in another context - the need for it in American education and what we have to do to achieve it. If we ignore this need, we will all suffer the consequences. And they will be upon us far sooner than the next century, barely a decade away. I think almost everyone in this room works for an organization that had to restructure in the 1980s. Mining companies that did not, just didn&apos;t make it. Well, we did. As an industry, we are seeing improved profits, positive cash flow, and a more competitive position in the world marketplace. But all the restructuring we have done, all the hard work, and all the pain that was part of it, will be in vain if, down the road, we do not have the educated people we need as workers. We need them to design, manufacture, and market the products that use the basic materials produced by the mining industry. Simply put, we are at a crisis point in education today. That is no new revelation. Nearly six years ago, the National Committee on Excellence in Education published its report, "A Nation At Risk." Since then, things have not gotten better. The Wall Street Journal, Business Week, US News & World Report, and Fortune have all recently published stories about the sorry state of education in the United States. The subject has become the topic of TV talk shows as well as national commissions, and for good reason. The pool of young people entering the US labor force is dwindling. In the next decade, 10 million fewer will enter the job market compared to the 1970s. But fewer of them will be qualified to do the jobs available to them. Here&apos;s why: • 20% of today&apos;s high school students drop out before they are 18 and another 20% graduate functionally illiterate; 40% of today&apos;s fourth graders think the world is flat; • 20% of today&apos;s sixth graders cannot locate the United States on a world map; • one of every three ninth graders cannot figure the change for a two-item meal - and I&apos;m talking about a Big Mac and fries. These are not just problems of minority kids in big city ghettos. Fully 40% of all young working Americans cannot add up their lunch bill. Three out of every five college freshmen need some kind of remedial work. These statistics are frightening. Particularly so because, while the work force is becoming less qualified and our public education system is getting worse, our products and technologies are becoming more complex. We are approaching a time when we will have machines that recognize handwriting but people who cannot write. We will have technology to take voice commands, but people who do not know what they are talking about. The accelerating pace of technology is changing the nature of the job market. The fastest growing jobs now, and in the years ahead, are in professional, technical, and sales positions requiring the highest education and skill levels. Most of these jobs will require the use of a computer. Yet, 95% of today&apos;s graduating high school students have never laid a finger on a computer keyboard. While our education system is failing the students it is supposed to serve, other countries are doing far better. In a

Jan 1, 1990

By N. S. Stoloff, K. R. Jordan

The temperatwe and grain size dependence of the mechanical avoperties of ordered and disordered Fe-49 pct Co-2 Pct V were investigated. The yield and flow stresses obeyed the Hall-Petch relationship u = ai + kd-&apos;I2. Ohdering reduced the intercept stress cjj and raised the Petch slope, k, at all temperatures. Ordering also increased the temperatwe dependence of k. The ductile to brittle transition temperature increased with order and grair~ size. Cleavage fracture was nucleation limited and the fracture stress did not zlary linearly with d-&apos;". A quantitative test of the Cottrell-Petch fracture theory (and recent modifications which consider the influence of slip mode), demonstvated that this theory is not applicable to FeCo-V. COTTRELL&apos; and etch&apos; independently suggested that a criterion for cleavage failure at the yield point, a,, based on dislocation pileups at a grain boundary or other obstacle to dislocat.ion motion, is: aYYkd&apos;I2 1 opy [ll or, equivalently, aikz,d112 +k:)bpy [2] where a, and ky are the Hall-Petch intercept and slope, respectively, 2d is the grain diameter, P is a geometric factor dependent on the macroscopic ratio between shear and tensile stress, p is the shear modulus, and y is the true elastic surface energy. When the product of quantities on the left side of the equation is equal to or exceeds that on the right, cracks should be able to nucleate and propagate at the yield stress, as shown schematically in Fig. 1. Therefore a high intercept stress, high Petch slope, or coarse grain size favors brittleness. petch3 associated the existence of a ductile to brittle transition in ferrous alloys with the temperature dependence of ai. One of the earliest modifications of the Cottrell-Petch theory was presented by ~rmstrong,~ who derived an expression for transition temperature in terms of several measurable flow and fracture parameters. The latter paper was able to rationalize situations in which the transition temperature increases with decl-easing grain size, as in the case of molybdenum,&apos; and also suggested that Ppy should be a function of grain size as well as temperature. More recently Johnston et a1.6 and Smith and worthington7 have suggested that the temperature or composition dependence ol&apos; ky must also be taken into account if there is any cha.nge in deformation mode, as from wavy to planar slip, or wavy slip to twinning, with change in temperature or solute content. Armstrong %as suggested that for hcp metals changes in o;k,dw> o;k,d1/2< / is / ^^^^ / / y_______________________________________ d-"2 Fig. l—Schematic representation of grain size dependence of yield stress, cry, and fracture stress, CTF. Intersection defined by Cottrell-Petch equation. slip mode should be incorporated in the theory through changes in the critical resolved shear stress for the slip system which controls ky. The purpose of the present investigation was to critically test the modified677 Cottrell-Petch theory of fracture in the superlattice alloy Fe-49 pct Co-2 pct V, by studying the grain size dependence of the yield and fracture stresses over a range of temperatures, in conjunction with an investigation of slip mode and fracture behavior. Previous work has shown that long range order results in a sharp decrease in flow stress, a small increase in work hardening rate and a drastic upward shift in the ductile-brittle transition temperature of F~CO-V.~&apos;~ The only comprehensive study of slip character in this alloy has been reported in a preliminary account of the present investigation.10 EXPERIMENTAL PROCEDURE The experimental work was carried out on material produced from a 10 lb vacuum melted ingot, of composition 49.32 wt pct Co, 2.09 wt pct V, balance Fe. 30-mil thick sheet samples with a 1; in. gage section were machined from cold rolled stock. The degree of cold work ranged from 85 pct for the finest grained samples to 5 pct for the coarsest grain size. Details of ingot fabrication are reported elsewhere." Equi-axed grain sizes in the range 12.7 to 75.4 p were obtained by annealing for varying times at 850°C. (Re-crystallization annealing time, rather than temperature , was varied to control grain size to insure that samples of all grain sizes contained equivalent quenched-in vacancy and interstitial concentrations.) Grain sizes were measured by the line intercept method on several specimens of each grain size. Following recrystallization, all samples were disordered by quenching into iced brine.

Jan 1, 1970

By Francis A Thomson

Montana Bureau of Mines and Geology, Montana School of Mines, Butte, Mont Francis A Thomson, President. The Bureau of Mines and Geology was formerly known as the Bureau of Mines and Metallurgy. A list of publications will be sent upon request¬ A series of six Bulletins and five Memoirs liave been issued by tlie Bureau, as well as several miscellaneous contributions Where the price is not indicated in tlie following selected list of those publications which are now available, the publications are presumably distributed gratis: Bulletin 3, Mechanical ore sampling in Montana, by H B Pulsifer (1920); 6, Geology and ore deposits of Bannack and Argenta, Montana, by P. J Slienon, 50 cents, Memoir 1, The Kevin-Sunburst and otlier oil and gas fields of the Sweetgrass Arcli, by E S Perry (1929), 2, Natural gas in Montana, by E S Perry (in preparation), 4, Tlie geologic structures of western Montana, by C H Clapp and others (in preparation), 5, Placer mining possibilities in Montana, by O A Dingman (1932).

Jan 1, 1933

By R. M. Treco

The effect of small additions of oxygen on the hardness, density, and lattice parameters of high purity zirconium has been investigated. Precision parameter values and density of oxygen-free zirconium are given as: a,, - 3.2258 kX units, C = 5.1373 kX units, O23 = 6.507 g per cc. THE effect of oxygen on the hexagonal-phase lattice constants of pure zirconium is of interest for several reasons. The extensive hardening effect of oxygen noted by previous investigators&apos; must be due in part to the lattice distortion accompanying its introduction and possibly to the preferred position of the oxygen atoms. De Boer and Fast&apos; have shown that oxygen is taken into solid solution in large amounts, appearing to occupy an interstitial position. These authors also found that expansion of the lattice was not uniform since the a axis attained a constant value after the addition of 10 atomic pct while the c axis continued to expand. It was thought in the present work that this expansion of the zirconium lattice with increasing amounts of oxygen

Jan 1, 1954

By P. R. Jones

The Bureau of Mines has written a computer program for the design and cost of a shell and tube type heat exchanger, in which a change in phase occurs on the shell side. The total cost, which was minimized, includes the annual fixed charges and annual operating costs. The program was written to meet the following requirements: (1) Triangular pitch, (2) single or multiple pass, and (3) heating or cooling. Price optimum design was obtained for four standard tube diameters and pitch. Standard heat exchangers whose area equaled or exceeded the required area are also listed. The program was made adaptable to various fluids and to various tube dimensions by including many of the required data such as physical properties of the fluids, tube data, and standard shell data as input data.

Jan 1, 1969

By Giovanni Principi

The activity of the ?Hydrogen Group? of Padova University, addressed to the study of materials for solid state hydrogen storage, is illustrated. Various Mg-based materials have been considered and are being studied: a) MgH2 and 0.5% mol Nb2O5 mixture ball milled under argon atmosphere; b) Mg-Ni-Fe intermetallic compounds prepared by short time ball milling of ribbons obtained by melt spinning and by long time ball milling of a mixture of MgH2, Ni and Fe powders; c) MgH2 ball milled in argon with Mm-Ni-Al (Mm = La-rich mishmetal) and Zr-Cr-Fe catalyst alloys. All the samples have been structurally characterized by X-ray diffraction (Rietveld refinement) before and after hydrogen absorption/desorption cycling and tested with a Sievert apparatus as regarding their thermodynamic and kinetic properties.

Jan 1, 2006

By G. G. Krishna Murthy

Interactions of wustite and hematite pellets with Fe-C melts were investigated experimentally by examining the effect of pellet size and bath temperature on the reduction rates of the pellets. Experiments were carried out in the temperature range 1473-1923 K. A flash X-ray equipment was used to obtain images of the melt surface during its reaction with an oxide pellet. The reduction rates were calculated using experimentally estimated time for complete reaction of a pellet, tR. The value of tR was determined employing gas mass flow rate, or pressure rise in the sealed furnace, versus time traces. The value of tR was the same for both wustite and hematite pellets of equal weight at or above 1723 K and it decreased with increasing melt temperature. But the reduction rate was substantially lower at temperatures below 1651 K, the melting point of wustite. The rates were defined as the rate of moles of oxygen removed from the pellet per unit area of bath free surface and it was found that the bath surface area affects the reduction rates. It was established that the overall reaction followed nth-order rate kinetics with the values of n falling between 0.3 and 0.4 for temperatures above the melting point of wustite. The apparent activation energy determined using the apparent rate constants obtained from the experimental data was 76.2 + 27.7 kJ/mol-O.

Jan 1, 1992

By D. A. Paice

Direct current electrical systems are used in most coal mines primarily to power the main haulage trains and secondarily to feed other equipment and passageway lighting. Electrical power is supplied from rotary machines or static rectifier equipment and is distributed through the mine by open trolley wires and feeder cables. The rails of the haulageway are used as a current return path. This exposed power distribution system is very vulnerable to conditions which lead to undesired leakage currents and short circuits and, consequently, the possibility of fires or other hazards to personnel. Present techniques and equipment have been utilized in so far as practical to improve the safety of the dc electrical system; however, there still appears a need for further improvement. Because of this need, this program was sponsored by the Bureau of Mines to investigate two specific technical areas related to improvement of dc electrical system safety. One area included the determination of the characteristics of mine electrical systems and their protection requirements and the verification of the adequacy of available protective devices for mine service. Despite the widespread application of industrial protective equipment in mines, there was little detailed technical information available related specifically to the performance of this equipment in service. Our task was not only to develop useful information regarding mine system protection, but also to define and verify the adequacy of the protective devices available. The second area of investigation called for development of a practical technique for detecting low level electrical fault or leakage currents. Conventional protective devices

Jan 1, 2012

E. Windsor Richards, London, England:—In reading this paper the most interesting point to me mas the question of the maximum percentage of phosphorus allowable in the steel rail. Mr. Colby said, and we will all agree with him, that the engineer knew, and even a steel-rail maker grants that phosphorus is the most undesirable constituent of steel. We in England have been for a long time considering a specification for the supply of steel rails. This matter has been taken up by the Institution of Civil Engineers, the Mechanical Engineers, the Iron and Steel Institute, the Institute of Naval Architects, and the Electrical Engineers. Committees have been formed,and the whole matter has received most careful attention. They arrived at last at an analysis which I will read: " The carbon is to be from 0.35 to 0.5 per cent.; the manganese from 0.7 to 1.0 per cent.; the silicon, not to exceed 0.10 per cent.; phosphorus, 0.07; and sulphur, 0.07 per cent." As to the phosphorus, which is the most important point of all in the analysis, we have for many years, and indeed until very lately, always agreed to supply steel which would not contain above 0.06 per cent. of phosphorus. Iron-ores are not quite as good now as they were formerly, and the manufacturers at the meetings of the committees referred to, tried to obtain an increase in the allowance of phosphorus. They asked the Sub-committee to agree to 0.08 per cent. of phosphorus. They tried all they possibly could to obtain that; but they failed. English engineers in Great George Street and all over England, representing the important Associa tions I have mentioned, would only agree to 0.07 per cent. and that is the maximum allowance of phosphorus. Mr. Colby is an able advocate, but with all his ability he would not have been able to persuade the English engineers to agree to 0.08 per cent.

Jan 1, 1907