电脉冲连续退火对AZ91镁合金带材组织和性能的影响

Influence of electropulsing continuous annealing on microstructure and properties of AZ91 Mg alloy strip

研究了电脉冲连续退火对冷轧时效态AZ91镁合金带材显微组织和力学性能的影响。结果表明:电脉冲退火在较低的温度下快速完成了α-Mg基体的再结晶,可显著细化晶粒。当退火温度为210℃时,α-Mg基体发生完全再结晶,其平均晶粒尺寸由冷轧态的约30μm减小为约7μm,带材的抗拉强度由冷轧态的410 MPa减小至334 MPa,断后伸长率由冷轧态的3.7%增大至23%。电脉冲退火后带材的拉伸断裂方式由冷轧态的脆性沿晶断裂转变为韧性穿晶断裂。电脉冲在其热效应和非热效应的共同作用下快速完成再结晶过程以及β-Mg17Al12相阻碍α-Mg基体晶粒长大,是电脉冲退火细化晶粒的主要原因。

Influences of electropulsing continuous annealing( EPCA) on microstructure and mechanical properties of cold-rolled aged AZ91 Mg alloy strip were studied. The results show that EPCA can rapidly complete the recrystallization of α-Mg matrix at relatively low temperature,and refinement of α-Mg grains is achieved. When the temperature of EPCA is 210 ℃,full recrystallization of α-Mg matrix occurred and the average grain size of the cold-rolled strip can reduce from 30 μm to 7 μm,the ultimate tensile strength of the cold-rolled strip decreases from 410 MPa to 334 MPa,and elongation to failure of the cold-rolled strip can increase from 3. 7% to 23%. Fracture surface of the alloy shows that transition from intergranular brittle facture to transgranular dimple fracture takes place after EPCA. The great grain refinement of α-Mg matrix is attributed to EPCA rapidly induced full-recrystallization resulting from the coupling of the thermal and thermal effects,and impeding effect of pre-existed β-Mg17Al12 particles on grain boundary moving of α-Mg grains.