Tensile properties and fracture mechanism of Al-Mg alloy subjected to equal channel angular pressing

Casting Al-2.77 wt.% Mg alloy was subjected to equal channel angular pressing (ECAP) and subsequent low-temperature annealing treatment. Tensile properties and fracture modes of as-ECAPed and annealed samples were investigated. It is found that the strength of the Al-Mg alloy increases with increasing the number of ECAP passes, while its elongation decreases. After annealing, the elongation is recovered to a large extent, consequently, the static toughness of the alloy is enhanced by a combination of ECAP and annealing treatment. Vickers hardness HV of the Al-Mg alloy monotonously increases with increasing the number of ECAP passes and follows a relationship of HV/σb ≈ 2.5, independent of the number of ECAP passes. Meanwhile, it is noted that the casting alloy only exhibits necking before failure, while the alloy subjected to ECAP fails in shear mode, with an increasing shear fracture angle at high number of ECAP passes. Besides, the low temperature annealing treatment hardly affects the tensile fracture mode of the ECAPed alloy. Based on the experimental results above, the tensile failure mechanisms of the ECAPed Al-Mg alloy are discussed.