Effect of iron and combined iron and beryllium additions on the fracture toughness and microstructures of squeeze-cast Al-7Si-0.3Mg alloy

Abstract

Squeeze casting is a near-net-shape process of casting under pressure that yields a fine-grain structure with higher density and mechanical properties compared to conventional casting processes. Iron is the most commonly present impurity element in Al-7Si-0.3Mg, the alloy investigated. An increase in iron content significantly decreases fracture toughness. However, trace additions of beryllium completely neutralize the detrimental effect of iron. The variables of the squeeze casting process greatly govern the microstructures and macrostructures and thus the defects in the casting. This case study deals with Al7Si-0.3Mg squeeze-cast cranks with four major defects—blistering, debonding, porosity, and patches of silicon segregation on the casting surface—and the appropriate remedial measures to eliminate these defects.