熔体温度对AZ31B镁合金铸态组织及力学性能的影响(英文)

Effects of melt temperature on as-cast structure and mechanical properties of AZ31B magnesium alloy

采用自制的电阻炉研究熔体温度对AZ31B镁合金凝固组织与拉伸性能的影响。结果表明:在温度低于850℃水冷时,金属型AZ31B镁合金铸锭等轴枝晶的尺寸随着熔体温度的升高呈直线下降,超过850℃后变化不大。组织中第二相呈现出先细化后粗化的变化规律。AZ31B镁合金试样的抗拉强度、伸长率和屈服强度随着熔体温度的提高而先快速增大后略有减小,熔体温度为850℃时试样的抗拉强度达到260MPa,屈服强度达到75.4MPa,伸长率达到27.57%,比熔体温度为750℃时的分别提高了15%、13%和61%。DSC分析表明,升高熔体温度使凝固开始点温度降低,临界晶核半径减小,从而增加了熔体中的过冷度,提高了熔体中非均匀形核率,是镁合金晶粒细化和拉伸性能提高的主要原因。

The effects of melt temperature on the as-cast structure and mechanical properties of AZ31B magnesium alloy were studied through a home-made electrical resistance furnace. The results show that the equiaxed dendrite size of AZ31B magnesium alloy under water-cooled metal cooling is linearly decreased with increasing the melt temperature below 850 °C, whereas the size changes little over 850 °C. The second phases in the microstructure are firstly refined;however, they are coarsened when the melt temperature exceeds 850 °C. With the increase of melt temperature, the tensile strength, yield strength and elongation of AZ31B magnesium alloy samples are rapidly enhanced first, then are slightly declined. When the melt temperature is increased to 850 °C, the tensile strength, yield strength and elongation reach 260 MPa, 75.4 MPa and 27.57%, respectively. The tensile strength, yield strength and elongation are increased by 15%, 13%and 61%, respectively compared with 750 °C. DSC analysis shows that the nucleation temperature is decreased, the critical nucleus radius is lessened with the increase of melt temperature, which increase the degree of supercooling and heterogeneity nucleation rate in melt, and the growth rate becomes larger with the increase of the degree of supercooling. That is the reason why the grain size is first rapidly decreased, and then is little increased.