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通过SEM、TEM和蠕变试验机研究不同温度下Mg-8Gd-2Nd-0.5Sb-0.6Zr(质量分数/%)合金高温蠕变行为,分析其组织演变,并通过计算合金的蠕变激活能分析蠕变机制。结果表明:加载应力10 h后,合金进入稳态蠕变阶段,随着温度升高蠕变性能差异明显增大;高温高应力情况下,组织上观察不到网状析出相,滑移线较多,存在孪晶,位错密度较高,此时网状析出β′相已经完全转变为颗粒状β相;蠕变温度在200、250、300℃下的应力指数为3.5、4.6和5.8,蠕变激活能为77.8、86.8、99.6 k J/mol。合金低温时受位错交滑移机制控制;高温时受扩散机制控制。
The creep behavior of Mg-8Gd-2Nd-0.5Sb-0.6Zr (mass fraction /%) alloy at high temperature was studied by SEM, TEM and creep tester. The microstructure evolution was analyzed. The creep activation energy Analysis of creep mechanism. The results show that the alloy creeps into the steady state at 10 h after loading, and the creep property increases obviously with the increase of temperature. Under the condition of high temperature and high stress, no net precipitated phase is observed in the microstructure, More twins exist and the density of dislocations is higher. At this time, the β ’phase precipitated by the network has completely transformed into the granular β phase. The stress exponent of the creep temperature at 200, 250 and 300 ℃ is 3.5, 4.6 and 5.8, The creep activation energy is 77.8, 86.8 and 99.6 kJ / mol. The alloys are controlled by dislocation cross-slip mechanism at low temperature and controlled by diffusion mechanism at high temperature.