Effect of Secondary Dendrite Arm Spacing on Tensile Property and Fatigue Behavior of A319 Aluminum Alloy

Abstract

A319 alloy with different secondary dendrite arm spacing(SDAS) was prepared by cutting samples from the cast ingot where locates at different distance from the bottom of the mold. The relationship between SDAS and porosity size, along with the relationship between SDAS and the ratio of size to aspect ratio of Si particles were investigated. Effects of SDAS on tensile properties, fatigue life and fatigue parameters were discussed. The results show that there is a linear relation between the ratio of size to aspect ratio of Si particles and SDAS. When SDAS is larger, Si particle size and the ratio of size to aspect ratio of Si particles, as well as porosity size are larger. SDAS almost had little effect on Young's modulus and yield strength, while with the increasing SDAS, the tensile strength, elongation and hardness all decrease. Furthermore, with the increasing SDAS, the fatigue life and fatigue parameters such as fatigue strength coefficient( σ′f), fatigue ductile coefficient( e′f) and fatigue ductile exponent( c0)all decrease, but as an exception, fatigue strength exponent( b0) increase.