Experimental investigation into effect of annealing treatment on springback of magnesium alloy sheets

Abstract

The purpose of this work is to experimentally investigate the effect of annealing treatment on the springback at room temperature for AZ31 magnesium alloy sheets, which were produced by rolling in a reversible warm mill after twin roll strip casting. Microstructure evolutions were investigated using optical microscopy after annealing at temperatures ranging from 350 to 450°C. Both tension and compression tests were performed at room temperature for the annealing treated samples to show the influence of annealing treatment on the asymmetric yielding behaviour of AZ31 Mg alloy sheets. In order to evaluate the springback in the stamping process, the V shaped air bending tests were performed and the angle changes after springback were measured. The tensile and compressive yield stresses were deteriorated because of the coarsening of grain size with increasing annealing temperature. The yielding behaviours of tension and compression show a large asymmetry, as well as the Hall–Petch slope. The Hall–Petch slope of the compressive yield stress is larger than that of the tensile yield stress. The springback angle in the V shaped air bending tests was decreased with increasing annealing temperature.

Keywords:

• Magnesium alloy sheet
• Annealing treatment
• Asymmetric yielding behaviour
• Springback