Microstructure and Mechanical Properties of A7075 Alloy with Additional Si Objects Fabricated by Selective Laser Melting

Recently, the realization of the combination of selective laser melting (SLM) and high-strength aluminum alloys (Al alloys) has been discussed in mainly the aerospace industry. However, there have been several problems for the realization, and the one of fundamental problem is the occurrence of microcracks in high-strength Al alloy objects fabricated by SLM. To solve the problem, some researchers have studied addition of alloying elements to high-strength Al alloy. In this study, we focused on the A7075 alloy with additional five% Si (A7075+5Si) and investigated the effects of the Si addition on the processability, microstructure, and mechanical properties. As a result, it was observed that the addition of Si element inhibited the formation of cracks in the A7075 objects. Our result suggests that high density and crack-free A7075+5Si objects had higher mechanical properties than the case of a conventional Al alloy (AlSi10Mg and AlSi12). However, the T6 heat treatment (After solution treatment, water quenching, and artificially ageing) did not increase the mechanical properties of A7075+5Si objects. In order to obtain the A7075+5Si objects with higher strength, it is required that the further studies about suitable heat treatment conditions for A7075+5Si alloy.