Low-cycle fatigue behavior of a cast Mg–Y–Nd–Zr alloy by T6 heat treatment

Abstract

Strain controlled low-cycle fatigue (LCF) tests of a cast Mg-3.5Y-2.4Nd-0.5Zr alloy by two different T6 heat treatment (T60: solution at 525°C for 4h and then aging at 225°C for 34h; T61: conditional industrial T6 heat treatment - solution at 520°C for 8h and aging at 225°C for 16h) were studied at room temperature under different total strain amplitudes. And theirs fatigue parameters, fatigue lives and failure behaviors after cyclic loading were evaluated. At relatively low total strain amplitudes (0.3–0.45%), the T60 alloy presented basically cyclic stabilization; and the T61 alloy was increasing hardening until failure. While at higher total strain amplitudes (0.45–0.9%), both them showed hardening through the entire LCF testing. Fatigue cracks of the alloy initiated from the specimen surface, the fracture surfaces became more rough and concavo-convex as the strain amplitude increased. Due to the fine and dense precipitates, the T60 alloy showed the super fatigue properties. And the alloy after T60 heat treatment obtained a distinctly longer fatigue life than that of the alloy treated under T61 condition at any given total strain amplitude.