Sintered Al–Si–Ni Alloy: Structure and Properties. II. Sintering and Forging

The presented study focuses on the development of a high-silicon Al-Si-Ni alloy with a coefficient of thermal expansion (CTE) comparable to that of steels, using powder metallurgy techniques.Experimental investigations are conducted to evaluate the effects of different sintering regimes-both liquid phase and solid one-on materials fabricated from elemental powder mixtures and ball-milled pre-alloyed powders.The results indicate that the optimal properties are achieved using a solid-phase sintering process followed by hot side setting and hot forging.This method results in a non-porous material with homogeneously distributed, fine spherical silicon inclusions, ranging from 1 to 7 m in size.Liquid-phase sintering is revealed impractical due to exudation, which leads to chemical-composition misrepresentation and the formation of course, cast-like structures with reduced mechanical properties.The use of pre-alloyed powders is determined to be preferable over elemental powder mixtures, as the latter results in porous materials with coarse intermetallic aggregates.The final alloy exhibits high mechanical properties, including yield strength of 221 MPa, ultimate tensile strength of 261 MPa, and hardness of 96 HB, alongside a CTE suitable for industrial applications.