Production and properties of brass-base P/M constructional materials. A review

Conclusions The best processing properties are exhibited by brass powders manufactured by the diffusional impregnation technique, using a zinc powder, brass swarf, or a copper-zinc master alloy as a point source. However, as this is a very labor-intensive process, normally preference should be given to melt atomization as a method of manufacture of brass powders. Brass P/M parts produced by the conventional method consisting of pressing a powder and sintering the resultant compacts have porosities of not less than 7–10%, and consequently this method is not widely used for the production of constructional brass parts. The sintering of compacts from copper and copper-zinc master alloy powders gives more stable zinc contents compared with the sintering of compacts from copper and zinc powders; the greatest stability of chemical composition is exhibited by sintered compacts from a homogenized brass powder. The formation of diffusional porosity accompanying the evaporation of zinc may be prevented by performing sintering in the presence of a liquid phase (which appears in the presence of a phosphorus or lead addition), saturating the sintering atmosphere with zinc vapor, and adding carbonates or halides of alkali and rare-earth metals to starting powders. The mechanical properties of materials can be markedly improved by eliminating their porosity. This may be achieved by subjecting porous preforms to hot forging, which enables brass P/M parts to be obtained whose mechanical properties are comparable to those of cast parts.Translated from Eoroshkovaya Metallurgiya, No. 3(255), pp. 56–64, March, 1984.     

Sintered constructional conducting copper parts for low-voltage units

Conclusions A process has been developed for the manufacture of copper conducting constructional parts of complex configuration by the powder metallurgy technique. The electrical resistivity of such sintered copper parts is virtually no different from that of parts from rolled copper. The operating characteristics of parts produced by this process are markedly superior to those of parts made from copper rolled stock.Translated from Poroshkovaya Metallurgiya, No. 10(202), pp. 100–103, October, 1979.The authors are indebted to I. G. Voronov, A. D. Bychkov, A. N. Butenko, and V. I. Tsilyurnik, formerly of the All-Union Scientific-Research Institute of Electrical Apparatus, for assistance with the preparation of specimens and determination of their characteristics.     

Production of powders from cast iron swarf and some features of the manufacture of parts from them. I. Production,structure, and properties of the powders

Translated from Poroshkovaya Metallurgiya, No. 7(319), pp. 4–9, July, 1989.     

Production of high-strength parts for constructional applications from multicomponent iron-base charges

Conclusions Calculation of the activity of carbon in multicomponent compositions enables a suitable choice to be made of compositions of alloyed charges made up of individual powdered elements (the base material being an iron powder), from which materials can be obtained with strength properties approaching those of rolled medium-alloy steels. The strength of such composites is determined by structure-formation processes, particularly those taking place in contact zones. The main role in these processes is played by the mobility of carbon.Translated from Poroshkovaya Metallurgiya, No. 11(239), pp. 61–64, November, 1982.     

Kinetics of heating of constructional parts of ferromagnetic powders in induction sintering

Translated from Poroshkovaya Metallurgiya, No. 7(307), pp. 49–53, July, 1988.     

铜粉对MIM钨铜合金组织和性能的影响

采用金属注射成形（MIM）技术制备了钨铜合金,定量表征了铜粉的粉末粒度和粒形,重点研究了铜粉粒度和粒形对MIM钨铜合金组织与性能的影响。通过对比铜粉的粒径、粒度分布宽度、长宽比、粗糙度、赘生物指数和钝度等特征参数,破碎铜粉与水雾化铜粉颗粒呈枝晶状,粒径远小于还原铜粉,但破碎铜粉粒度分布宽,微观结构上的规则度、表面光滑程度以及分散程度最佳。破碎铜粉混合钨粉为原料,通过MIM技术制备钨铜注射生坯致密度高、缺陷少,烧结后钨铜合金的组织与性能最优,致密度为96.2%,硬度为235HV,抗弯强度为1 200 MPa,热导率为128 W/(m·K),电导率为30%IACS。     

Production of Nd-Fe-B alloy powders using high-pressure gas atomization and their hard magnetic properties

Fine spherical Nd−Fe−B powders with a tetragonal Nd₂Fe₁₄B phase have been produced by high pressure argon or helium atomization. The average size defined by 50 pct cumulative weight fraction is as small as about 25 μm. The Curie temperature of the powders is about 580 K and the intrinsic coercivity (iH _c ) of the bonded products made from the powders increases with decreasing particle size and reaches about 0.581 MA/m for the powder below 25 μm diameter. TheiH _c value increases with an increase in the cooling rate by helium atomization as well as with an increase in neodymium and boron content to 18 at. pct Nd and 12 at. pct B with the highestiH _c value reaching 0.716 MA/m. Annealing in the range of 773 to 1073 K gives rise to a further increase ofiH _c to 1.035 MA/m. The highiH _c value is promising for practical use as isotropic bonded powder magnets. The increase of magnetization for the bonded powder magnets takes place rapidly and the behavior is similar to that for sintered Nd−Fe−B magnets, in goods contrast to a sluggish increase of magnetization for the bonded Nd−Fe−B powder magnets made from the comminuted powders of melt-spun ribbon. From the magnetization behavior, it was presumed that the generation of the large intrinsic coercivity is due to the difficulty of the nucleation of reverse domain rather than the pinning of domain walls.     

Production of powders from cast iron swarf and some features of the manufacture of parts from them. II. Some features of the manufacture of P/M parts and their structure and properties

Conclusions Increasing the amount of cast iron powder in such a charge and raising the sintering temperature of compacts result in the formation in the alloy structure of a coarse cementite network among the grains and a fine cementite network along the slip lines. Consequently, what is needed to increase the strength of the synthesized alloys is either a low rate of cooling in sintering or additional heat treatment, designed to prevent the presence of structurally free cementite in the structure of the finished alloys. The optimum sintering temperatures for the iron-cast iron materials in an endothermic gas atmosphere, ensuring the highest strength properties in finished P/M parts, is 1200°C. Alloys containing 10 and 20% cast iron can be recommended for construction applications, and others, for the manufacture of parts operating under conditions of friction and increased wear without dynamic loads. These include the components of the pump unit of the rotary compressor of a domestic air conditioner.Translated from Poroshkovaya Metallurgiya, No. 9(321), pp. 4–10, September, 1989.