TECHNOLOGIES
Effect of production technique on a high silicon al-si-ni sintered alloy structure and properties
An experimental study was carried out to develop a technique for manufacturing a high silicon Al-Si-Ni sintered alloy with a coefficient of thermal expansion close to steels. A stage of hot forging was added to overcome porosity and improve silicon inclusions morphology to obtain better mechanical properties. Liquid and solid phase regimes of sintering were studied for the material made of the elemental components powders mixture as well as of a pre-alloyed powder. The impracticality of liquid-phase sintering modes is shown for this type of material primarily because of the tendency to liquid-phase exudation. It was proposed to carry out a solid-state vacuum sintering with subsequent hot deformation. Only the pre-alloyed powder is suitable for the technique; the other way, it leads to the course and sometimes, not equilibrium intermetallic inclusions will form in place of nickel particles because of the insolubility of Ni in solid Al. It is shown the possibility of successful plastic deformation of this material after sintering despite its extremely low ductility, which helps successfully overcome porosity and improve the characteristics of the microstructure of the material.