Effect of Heat Treatment on the Mechanical Properties of a Nanodispersed Al-16Si-5Fe-1Cu-0.5Mg-0.9Zr Alloy

초록

A hypereutectic Al-Si based alloy has a low density, low thermal expansion coefficient and good wear resistance, which are essential requirements for the structural materials in the field of advanced transportation systems. In this study, a hypereutectic Al-16Si-5Fe-1Cu-0.5Mg-0.9Zr (wt%) alloy having about 300nm-sized dispersoids involving an Al-Fe-Si based intermetallic phase and 800nm-sized grains was fabricated by a gas atomization technique and subsequent powder extrusion. Using the extruded material, various heat treatments were conducted to clarify the relationship between microstructure/mechanical properties/heat treatment condition for the extruded alloy. The value of Vickers hardness for the extruded alloy did not change markedly with the isothermal heat treatment up to 673 K, although it decreased abruptly with further increase in the isothermal heat teatment temperature. The rapid decrease in the hardness was considered to occur mainly by the growth of dispersoids. When the extruded alloy was held at 463 K after quenching from 793 K, Vickers hardness increased with increasing holding time and showed the maximum value at about 9.6 ks. It was considered that the increment in the hardness is related to the precipitation of a nano-sized Al-Cu based intermetallic compound.