Showing papers on "Powder metallurgy published in 1984"

Powder metallurgy of superalloys

Abstract: Nickel-chromium and, to a lesser extent, cobalt-chromium alloys are the major class of materials used for the high temperature components of aircraft, marine, and land-based power systems and are a...

Aluminum-lithium alloys II

Abstract: The topics covered in this volume include: methods of alloy preparation (including ingot casting, rapid solidification, and mechanical alloying); processing and alloying effects on microstructure and properties; superplastic deformation; and physical metallurgy fundamentals. Other topics discussed include: weldability; sodium and hydrogen effects on fracture; corrosion behavior (including general corrosion, stress corrosion, and high-temperature oxidation); and monotonic and cyclic properties at ambient and elevated temperatures. Attention is also given to the use of Al-Li alloys in aircraft structures.

Dispersion-strengthened heat- and wear-resistant aluminum alloy and process for producing same

Abstract: A light weight and high strength aluminum alloy and a process for producing such an alloy, which alloy is suitable for forming automotive engine components, including pistons. In a preferred embodiment, 80 to 99.5% by volume of an aluminum alloy powder or a mixed powder composed of pure metal powders or master alloy powders is blended with 0.5 to 20% by volume of at least one of carbon or graphite powder, an oxide powder, a carbide powder and a nitride powder. The blend is then mechanically alloyed, following which the thereby-obtained powder is subjected to working such as by compaction and hot forging, hot pressing, cold isostatic pressing and hot forging, or cold isostatic pressing and hot extrusion. By the use of mechanical alloying, the advantages of a rapidly solidified powder having a supersaturated solid solution and uniform fine crystal grains are attained, and the effect of dispersion-strengthening is brought about by the addition of dispersion particles to the micro structure of the rapidly solidified powder.

Modern developments in powder metallurgy

Abstract: This book presents the papers given at a conference on metal powders. Topics considered at the conference included sintering fundamentals, liquid phase and activated sintering, stainless steels, copper-base powder metallurgy, aluminium alloys, refractory metals, carbides, cutting tools, friction, wear, and powder production.

Elimination of Pores During Liquid Phase Sintering of Mo—Ni

Abstract: The elimination of isolated large pores during liquid phase sintering has been studied in a 96Mo–4Ni alloy (wt-%). The large pores have been produced at the site of spherical Ni particles upon thei...

Powder Metallurgy of Light Metal Alloys for Demanding Applications

Abstract: Powder metallurgy (P/M) processing offers advantages over conventional processing for both the aluminum and titanium systems. For aluminum, rapid solidification and mechanical attrition processes produce P/M alloys having improved mechanical and corrosion properties. The processing of these materials and the alloy classes being exploited—high strength/corrosion resistant, reduced density/increased modulus, and high-temperature alloys—are discussed. For titanium, the P/M approach has generally been used to reduce costs. However, recent improvements in properties, due to rapid solidification, in both conventional (Ti-6Al-4V) and new alloys have been obtained. The state of the art in these two alloy systems is presented and future developments projected.

Titanium Net-Shape Technologies

Abstract: To determine the state of progress in the major areas of titanium net-shape development a symposium was held at the AIME Annual Meeting in February 1984. Editor’s Note: The proceedings, Titanium Net-Shape Technologies edited by F.R. Froes, and D. Eylon, will be published by The Metallurgical Society of AIME in 1984. The following extended abstracts discuss some aspects of precision casting, isothermal forging, and powder metallurgy that have stimulated aerospace and industrial applications of titanium net-shape parts.

Casting having wear resistant compacts and method of manufacture

Abstract: This invention relates to a double composite structure comprising cemented carbides embedded in an austenitic stainless steel matrix forming a wear, impact, drill and corrosion resistant shape by powder metallurgy techniques. Molten metal is then cast around the composite structure forming the body of a tool, lock or parts which are particularly useful for earthmoving and security applications.

The Microstructure and tensile properties of a splat-quenched Al-Cu-Li-Mg-Zr alloy

Abstract: The microstructure and tensile behavior of an Al-3Cu-l.6Li-0.8Mg-0.2Zr alloy, produced by splatquenched powder metallurgy processing, were studied. The alloy exhibited homogeneous deformation, both in bulk samples and duringin situ TEM studies. This is in contrast to the strain localization that is frequently observed in Mg-free Al-Cu-Li-X alloys. The difference in deformation mode is attributed to a fine distribution of Ś (Al2CuMg) which precipitates up to the grain boundaries. A processing treatment involving 2 pct stretch prior to aging resulted in a yield strength of 555 MPa, a reduction in area of 29 pct, and a strain to fracture of 8.8 pct. This represents an attractive improvement in specific properties compared with 7075-T76 having a similar texture.

Alloys based on NiAl for high temperature applications

Abstract: The NiAl alloys for potential high temperature applications were studied. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some ternary alloying additions (Hf, Ta and Nb) were identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. The effects of grain size and stoichiometry in binary alloys are also presented.

Sinterability, strength and oxidation of alpha silicon carbide powders

Abstract: An investigation is made of pressureless sintering of commercially available alpha-SiC powders at temperatures between 1900 and 2150 C for periods of 10 to 240 min under one atmosphere of argon pressure. It is found that alpha-SiC powder containing boron and carbon sintering aids is sinterable at 2150 C for a period of 30 min to a high final density (greater than 96 percent of theoretical). In alpha-SiC powder containing aluminum and carbon sintering aids, the final density achieved is only about 80 percent of theoretical. Determinations are made of room temperature and high temperature (1370 C) flexure strength and oxidation resistance on sintered high density (more than 96 percent of theoretical) alpha-SiC (boron, carbon) material. It is found that both the strength and the resistance to oxidation are equivalent and comparable to those of the sintered alpha-SiC which represents the state of the art.

Sintering of new oxide ceramics using a high power cw CO2 laser

Abstract: The sintering of ceramic oxide powders has been investigated using a high power CO2 laser as the heat source. The laser sintering method is very useful for the densification of oxides such as ZrO2, HfO2, and Y2O3 which have high melting points above 2000 °C. The new ceramic in the ternary system of (ZrO2‐Y2O3‐HfO2) processed by the laser method has a high melting point (2850 °C) and a hardness of about 1800 kg/mm2. The new oxide ceramic is composed of the crystalline phase of tetragonal ZrO2 and ZrO2 HfO2 Y2O3 solid solution, and does not show any phase transitions at high temperatures.

The influence of gas atmospheres on the first-stage sintering of high-purity niobium powders

Abstract: Niobium and tantalum surfaces easily absorb oxygen. With decreasing particle size the content of oxygen increases. The role of this surface oxygen and oxygen in the sintering atmospheres on the first-stage sintering is not well established. Therefore the sintering behavior of high-purity niobium powders was studied by annealing cylindrical powder compacts (particle size 3000 min-1) to temperatures above the melting point of Nb2O5 (Tm = 1495 °C) enhances the neck growth due to the formation of a liquid oxide phase on the surface of the powder particles.

Oxidation resistant slurry coating for carbon-based materials

Abstract: An oxidation resistant coating is produced on carbon-base materials, and the same processing step effects an infiltration of the substrate with silicon containing material. The process comprises making a slurry of nickel and silicon powders in a nitrocellulose lacquer, spraying onto the graphite or carbon-carbon substrate, and sintering in vacuum to form a fused coating that wets and covers the surface as well as penetrates into the pores of the substrate. Optimum wetting and infiltration occurs in the range of Ni-60 w/o Si to Ni-90 w/o Si with deposited thicknesses of 25-100 mg/cm 2 . Sintering temperatures of about 1200° C. to about 1400° C. are used, depending on the melting point of the specific coating composition. The sintered coating results in Ni-Si intermetallic phases and SiC, both of which are highly oxidation resistant. The final coating composition can be further controlled by the length of the sintering time.

Sintering and microstructure development of glass-bonded silver thick films

Abstract: The sintering of glass-bonded silver thick films has been studied by dilatometry and microscopic analysis. Effects of particulate characteristics of silver and glass frit powders, glass composition, silver/glass ratio, and substrate materials have been discussed. It is shown that the silver-glass interaction is one of the most important factors responsible for the microstructure. Most of all, glasses promoted the densification of the thick film. Microstructure development has been understood by the stage of sintering as determined by the combined effects of temperature and silver/glass ratio.

Isostatic compression technique for powder metallurgy

Abstract: Powder metallurgy products of high tensile strength are formed in a pore-free state by a novel process which entirely avoids the use of canisters. An open-pore specimen is purged with depurative gas, backfilled with a reactive gas and, while still immersed in the reactive gas, compressed isostatically to an extent necessary to close the pores. The specimen may then be compressed to full density without the need for either high vacuum or a depurative or reactive gas atmosphere.

Retarded grain boundary mobility in activated sintered molybdenum

Abstract: Rapid grain growth accompanies the enhanced sintering of molybdenum treated with nickel additions. Grain growth is detrimental to sintering kinetics and mechanical properties. A sintering model is developed to illustrate that reducing grain boundary mobility is a means to increase the densification rate. A fine silica dispersion is added to molybdenum powder which is activated by the addition of nickel. This powder exhibits a long term sintering benefit due to retarded grain growth which is attributed to dispersoid drag effects on grain boundaries. These experimental powders are further analyzed through precision dilatometry, showing a characteristic shift in shrinkage rate during constant heating rate experiments. The shrinkage rate of molybdenum is increased by a factor of 10 at 1000°C when activated with 0.37 pct Ni. The shrinkage rate of nickel activated molybdenum is further increased by 67 pct with 1400 ppm silica dispersed at the interparticle grain boundaries.

Squeeze casting of carbon fibre-tin alloy composites

Abstract: Description du procede. Observation par microscopie electronique des composites ainsi obtenus

Vacuum sintered powder alloy dental prosthetic device and oven to form same

Abstract: An alloyed metal dental prosthetic device, such as a coping, of an alloy dental reconstructive element, is formed from a liquid phase sintered powdered metal alloy at elevated temperatures of about 1000°-1300° C. under a high level of vacuum of about 10 to 1000 microns of Hg. A special oven is devised which will achieve this high level of vacuum in a rapid efficient manner. The resultant metal prosthetic device has the density of at least that found in commercial cast prosthetic devices.

Alloy steel powder for powder metallurgy and its production

Abstract: PURPOSE: To obtain alloy steel powder for powder metallurgy having excellent compressibility by diffusing and sticking a powder alloy consisting of plural components to the surface of iron or steel powder and specifying the concn. of the respective alloys diffused and stuck to the iron or steel powder having a prescribed grain size. CONSTITUTION: Ni and Mo which are the alloy components to suppress and control the reaction of steel powder and C are dispersed in the form of fine metallic powder or the compd. thereof into a liquid (methyl alcohol, etc.) which does not dissolve such components. The liquid and the iron or steel powder are thoroughly mixed to stick the alloy components to the surface of the iron or steel powder than the powder is dried. The iron or steel powder is then treated in a reducing atmosphere to diffuse the Ni and Mo to the surface thereof. The concn. of the Ni and Mo diffused and stuck to the iron or steel powder having ≤44μ grain size is maintained within the concn. range of 0.8W1.9 times the concn. of the Ni and Mo diffused and stuck to the entire iron or steel powder. The upper limit of the Ni is specified to 10.0wt% and the upper limit of the Mo to 0.1W0.4wt%. High toughness is obtd. if the sintered body for which such iron powder is used is subjected to a carburization treatment. COPYRIGHT: (C)1986,JPO&Japio

High temperature properties of equiatomic FeAl with ternary additions

Abstract: The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exits over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at % ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with prealloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.