显微组织和织构对AZ31B镁合金成形性能的影响

摘要

The effect of the repeated unidirectional bending (RUB) process and annealing on the formability of magnesium alloy sheets was investigated. The RUB process and annealing treatments produce two effects on microstructure: grain coarsening and weakening of the texture. The sheet that underwent RUB and was annealed at 300 ℃ exhibits the best formability owing to the reduction of the (0002) basal texture intensity, which results in low yield strength, large fracture elongation, small Lankford value (r-value) and large strain hardening exponent (n-value). Compared with the as-received sheet, the coarse-grain sheet produced by RUB and annealing at 400 ℃ exhibits lower tensile properties but higher formability. The phenomenon is because the deformation twin enhanced by grain coarsening can accommodate the strain of thickness.%通过单向多道次弯曲(RUB)工艺及随后的退火处理来改变镁合金的显微组织和织构,研究显微组织和织构对其成形性能的影响.RUB工艺和不同温度下的退火处理对显微组织有两方面的影响:粗化晶粒和削弱织构.经RUB处理并在300℃退火的板材表现出最好的成形性能.这主要归因于(0002)基面织构强度的削弱,而织构的削弱导致了较低的屈服强度、较大的断裂伸长率、较小的Lankford值(r值)和较大的加工硬化指数(n值).与原始板材相比,经RUB处理并在400℃退火而产生的具有粗大晶粒的板材具有较低的拉伸性能,但却表现出较高的成形性能.这主要是由于粗大晶粒增强了变形孪晶,而变形孪晶可以协调厚向应变.