Microstructure and hardness of zirconium diboride reinforced Al-Si matrix composite

Al-Si casting alloy AA4032 are widely used in the automotive industry, especially piston parts, which is required to be worked at high-temperatures. Therefore, the mechanical properties improvement of this alloy is necessary. In this research work, the AA4032 with the high Cu matrix composites reinforced by in-situ zirconium diboride (ZrB2) particles were conducted to investigate the characteristics of microstructural and hardness. The ZrB2 metal matrix composite was produced by the in-situ reaction of molten aluminum with inorganic salts K2ZrF6 and KBF4. The results revealed that the amount of primary Si particles increased with increasing Cu addition from 1 wt.% to 3.5 wt.%. This indicated that Cu addition shifted the eutectic point in the alloy system. However, the ZrB2 addition resulted in complete elimination of primary Si particles and refinement of eutectic Si phases. XRD and SEM analysis show that ZrB2 reinforcement has been obtained and been distributed in the aluminum matrix. It is seen that there is an increase in hardness of the material after reinforcement from 113.3 HB to 118.2 HB.