Effect of annealing treatment on microstructure and property of Er-containing Al-Mg-Zn alloys

Abstract

Effect of annealing treatment on tensile properties, intergranular corrosion, macrostructure and microstructure of Al-6.0Mg-1.0Zn-0.8Mn-0.2Cu-0.2Er-0.1Zr hot-rolled plate as studied by hardness testing, tensile testing, intergranular corrosion, OM, EBSD and TEM. The results show that the stabilization work window of the plate is 230℃/18 h, 240℃/6 h and 250-270℃/2 h. After 250℃/2 h, the alloy plate presents the best comprehensive performance with 263 MPa yield strength and 6.732 mg/cm2 mass loss. 250℃/2 h is selected as the optimal stabilization process for hot rolled plate by combining the mechanical properties and corrosion resistance. Through selected area electron diffraction (SEAD) and energy spectrum analysis, the second phase at the grain boundary and in the grain are all the T-Mg32(AlZn)49 phases. After annealing at 250℃/2 h, the T phase in grains gradually grows up and re-dissolves, and the morphology changes from square to short rod. The T phase are discontinuous and the spacing becomes larger at grain boundary, which shows good corrosion resistance.

Keywords

• er containing al-mg-zn alloy
• stabilization
• intergranular corrosion
• t phase
• mechanical property