Investigation of Microstructure and Mechanical Properties of AlSi7Mg0.3Cu0.5 Alloy with Addition of Zr, Ti and Sr

Abstract

The main objective of this paper is to investigate the effect of Zr and its synergistic effect together with the addition of an inoculant (Ti) and a modifier (Sr) in terms of structural analysis and mechanical characteristics of AlSi7Mg0.3Cu0.5 alloy. In accordance with the objectives of the paper, in the experimental part, eight material variants were cast by the investment casting method. The presence of Zr in the experimental alloys was manifested by the crystallization of phases with different chemical compositions mainly (AlSi)3(TiZr) and (AlSi)2(TiZr). The graded addition of Ti in the alloys resulted in a higher number of nucleation grains of Zr-rich phases, and alloys with a combination of Zr and Sr were characterized by the formation of (AlSi)2(TiZr) phases. Various types of precipitates based on Zr (Al3(ZrTi)) and Cu (Al2Cu) were observed in the substructure of the alloys. The addition of Zr and its synergistic effect with Ti and Sr led to an increase in the conventional yield strength, hardness and partly tensile strength with reduced elongation of the experimental alloys.

Zr as an Alternative Grain Refiner in the Novel AlSi5Cu2Mg Alloy

“…This strengthening effect leads to an increase in the strength of the material, as indicated by the increased microhardness [42][43][44]. The second factor is the presence of Zr itself in the aluminum matrix (and probably also in the substructure, as demonstrated by our previous research [45]), because Zr is characterized by high hardness [25]. Figure 7b,c shows the presence and uniform distribution of Zr in the aluminum matrix.…”