Effect of Addition of Mn, Cr, Sr, Be, P on the Fragmentation and Dissolution of β-Al₅FeSi Platelets in Fe Containing Al-Si and Al-Si-Cu-Mg Cast Alloys: Role of Solution Treatment

The present investigations were carried out on industrial Al-Si-Cu-Mg alloys containing Fe up to 1.5%. Effect of additions of small amounts of Mn, Cr, Sr, Be, and P on the characteristics of β-platelets were examined using field emission scanning electron microscopy in as-cast samples obtained at varying solidification rates. Fragmentation and dissolution of the β-platelets as a function of solutionizing temperature (500 °C and 540 °C) and solutionizing time (0-100 h) were analyzed. The relationship between the tensile properties and the solutionizing treatment has been established. The results show that addition of 0.7%Mn to the G2F alloy improves the yield strength (YS) value by 45%, and ultimate tensile strength (UTS) value by 160%. The combined addition of 0.7%Mn +0.13%Cr resulted in improving the YS and UTS values by 35% and 220%, respectively. The presence of Be (~ 0.13%) caused the precipitation of the Al₈Fe₂BeSi phase in a Chinese-like pattern in addition to the precipitation of fine platelets. The alloys G2FS2B (250 ppm Sr + 0.13%Be) and G2F2SB (450 ppm Sr +0.13%Be) showed increases in the UTS values of 50% and 35%. Mn + Cr can be replaced by 0.02% Sr + 0.13% Be.