Mg-Gd-Y-Mn耐热镁合金的压缩变形行为研究

Deformation behavior of Mg-Gd-Y-Mn heat resistant magnesium alloy during hot-compression

采用Gleeble-1500热模拟机对Mg-Gd-Y-Mn稀土镁合金在温度为300～500℃、应变速率为0.001～1.0s-1、最大变形程度为60%的条件下,进行恒应变速率高温压缩模拟实验研究.分析了实验合金高温变形时流变应力与应变速率及变形温度之间的关系以及组织变化,计算了表观激活能及相应的应力指数,为选择这种合金的热变形加工条件提供了实验依据.结果表明:合金的稳态流变应力随应变速率的增大而增大,在恒应变速率条件下,合金的真应力水平随温度的升高而降低;在给定的变形条件下,计算得出的表观激活能和应力指数分别为200kJ·mol-1和5.1.根据实验分析,合金的热加工宜在400～500℃温度范围内进行.

The stress-strain behavior of Mg-8.75%Gd-3.82%Y-0.54%Mn (mass fraction, %) alloy was investigated. The test was carried out in a strain rate range of 0.001-1.0s-1 and at temperatures 300-500°C and at maximum strain of 60% on a hot-simulation machine-Gleeble-1500. The relationship among true stress, true strain and deformation temperature and microstructure of the tested alloy were studied during hot-compression. The apparent deformation activation energy and corresponding stress exponent under hot-compression have been evaluated quantitatively. The results provide the experimental basis for selecting hot wrought conditions of the alloy. The relation between stress and strain is obviously affected by strain rate and deformation temperature. The steady flow stress increases with increasing strain rate at the constant temperature, and decreases with increase of deformation temperature at the constant strain rate. The apparent deformation activation energy increases markedly in the range of 400-500°C, no more change in the range of 300-400°C, the apparent activation energy 280kJ/mol and the corresponding stress exponent 5.1 are determined, respectively. The temperature range of 400-500°C for hot-working deformation of this alloy is suggested.