Fracture Toughness in an Extruded ZK60 Magnesium Alloy

Examination of fracture toughness has been performed a commercial Mg-Zn-Zr alloy, ZK60, with fine strengthening particles. The commercial alloy was extruded at 633 K, and then heat treated at specific conditions. The microstructures were equi-axed grains, and average grain size and precipitate size were 11.6 (mu)m and 50–150 nm, respectively. The yield strength and elongation-to-failure were 225 MPa and 17.0%. The plane-strain fracture toughness, KIC, was estimated to be 20.6 MPam1/2 in stretched zone analysis. From ductile fracture model, all the finer particles did not affect the void formation. The precipitates having a large diameter, more than 100 nm, were supposed to be the origin of void formation.