Production of nanocomposites by sintering iron-copper powder

Iron-copper nanopowder may be obtained by the reduction of hydroxides in hydrogen. The particles of this powder consist of iron cores within thin copper shells. Sintering of such powder produces a nanocomposite (density 6.9–7.1 g/cm³), whose microhardness (1300–1500 N/mm²) is more than triple that of regular Fe-Cu crystallites.     

Structurization in the sintering of heterophase materials TiN-Ni

Conclusions As a result of the investigation of the structurization in the quasibinary system TiN-Ni after high-temperature liquid-phase and low-temperature solid-phase sintering it was established that structurization in short-term liquid-phase sintering is accompanied by the denitration of TiN, decrease of its microhardness, change of the compositon of its metal bond and of its amount in consequence of diffusion of Ti from TiN (formation of the eutectic Ti(Ni) + Ni₃Ti).The considerable increase of microhardness of grains of TiN and the linear increase of its lattice period after lengthy isothermal sintering are due to the dissolution of nickel in TiN. In the metal bond there appear excess crystals of Ni₃Ti and of the eutectic Ni₃Ti + TiNi.The growth of TiN grains in the heterophase material TiN-Ni proceeds by the mechanism of coalescence and dissolution-segregation. After solid-phase sintering the phase composition of Ni and TiN did not change, the grain size of TiN remained stable.Translated from Poroshkovaya Metallurgiya, No. 4(328), pp. 25–30, April, 1990.     

Pb在快凝Al-Si基减摩材料中的作用

研究AJ-Si基减摩材料中Pb含量与材料力学性能和摩擦磨损特性的关系，分析了材料的微观组织，结果表明，Pb能够提高减摩性能，改善材料的摩擦磨损特性。     

Swelling during sintering of titanium alloys based on titanium hydride powder

Abstract

Compacts were prepared by pressing titanium and titanium hydride powders mixed with nickel powder and sintering under vacuum. Severe swelling was observed only for compacts based on TiH₂ powder. Pressure changes in the vacuum furnace, dilatometry results and mass loss data all indicate that dehydrogenation of TiH₂ powder compacts occurs at lower temperature than any significant sintering. Swelling appears to have been caused by a contaminant in the TiH₂ powder rather than hydrogen. The onset of severe swelling during heating was associated with the formation of liquid phase as the solidus was crossed. However, some swelling appears to take place under solid state sintering conditions. Various results indicate that the mechanism of swelling is high gas pressure within closed pores. Large pores appear to form by breakage of ligaments between small pores followed by opening of the pore. It appears that the use of (uncontaminated) TiH₂ powder in place of Ti powder would allow the benefit of lower green porosity to be retained during sintering to achieve low sintered porosity.     

Liquid-phase sintering of aluminum-based powder alloys

Specific features of liquid-phase sintering of aluminum-based powder alloys (PA) are investigated. The volumetric changes for binary, ternary, and quaternary PAs during sintering are shown to be caused by the diffusion nature of the interaction between the solid and liquid phases. The use of exothermic sintering made it possible to develop methods for obtaining binary PAs. Optimal modes of obtaining ternary and quaternary PAs are found.     

New self-lubricating antifriction materials based on titanium nitride

Tribological properties of powder composite materials of the skeletal and matrix types are studie under conditions of dry friction with rates up to 10 m/sec in air in pair with steels. Titanium nitride is used in order to obtain skeletons, and the matrix is polytetrafluoroethylene (PTFE). It is established that the tribological properties depend on the type of structure. In level of wear resistance materials of the skeletal type surpass by a factor of 1.5 the original compact materials, and filled PTFE by a factor of eight to nine. Use of PTFE makes it possible to improve markedly the tribological properties of composite materials based on titanium nitride and to reduce significantly (up to 40%) the weight of friction assemblies.     

The sintering of Cu-Cd and Ag-Cd powder alloys

Summary An experimental investigation was carried out into the processes taking place during the sintering of powder alloys of the systems Cu-Cd and Ag-Cd. The method of sintering Cu-Cd and Ag-Cd alloys with a given cadmium content is discussed. Results are presented of tests of electrical breaking contacts made of a Cu-Cd (99% Cu, 1%Cd) and a Ag-Cd-base (76.5%Ag, 22% Cd, 1%Ni, 0.5%Fe) powder alloys.     

Properties of iron-copper master alloy powder

The advantages of low-alloy sintered materials produced from iron—copper master alloy are confirmed. Physical and technological properties of the master alloy powders are determined. Experiments show that mixtures of iron, graphite, and iron—copper powders compact well to produce high-quality articles. Sintered materials have strength values (σ_f ～ 345 MPa, HB ～ 1430 MPa) comparable with those of similar materials produced using electrolytic copper.     

Consolidation processes in the sintering of fine-grained iron-copper pseudo-alloys

The properties of fine-grained iron-copper pseudo-alloys (ICPA) and consolidation processes that occur during their sintering are studied. The grains are no larger than 0.5 μm. It was established that the specimens undergo shrinkage, not growth, when fine iron-copper mixtures are sintered within the range 600–1130 °C. This occurs as a result of active consolidation of the dispersed powder mixture, shortening of the diffusion paths, and the active formation of solid solutions based on iron and copper. Sintered ICPAs have a stable fine-grained microstructure with a maximum grain size of 0.5 μm only when they are sintered and treated in the solid phase. A coarse-grained structure is formed when ICPAs are heated to temperatures at which a liquid phase appears. Fine-grained ICPAs are also characterized by high hardness (up to 240–260 HB). Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 22–29, January–February, 2000.