高温低应力下AZ31镁合金的蠕变性能及蠕变机理

Creep Property and Mechanism of AZ31 Magnesium Alloy under High Temperature and Low Stress

研究了AZ31镁合金在高温、低应力下的蠕变性能及蠕变机理。结果表明,AZ31镁合金的高温蠕变具有明显的三阶段蠕变特征;随着温度和应力的增加,稳态蠕变速率增加,稳态蠕变速率区域缩短。温度大于420℃、较低应力时,AZ31镁合金的蠕变为晶界扩散控制的COBLE蠕变;较高应力时,与位错攀移控制的WEETMAN蠕变机制相吻合。当温度为320～420℃时,AZ31镁合金的蠕变为滑移控制的位错蠕变。计算了由COBLE蠕变向WEETMAN蠕变转变的临界应力σcr,该应力与P-N力τp在数值上具有如下关系:σcr≈(2～3)τp。

The creep property and mechanism of AZ31 magnesium alloy under high temperature and low stress is investigated. The results show that the creep curve presents obviously the three stages creep characteristic. The creep rate increases and the static creep stage shortens with increasing temperature and stress. When temperature is above 420℃, the creep of AZ31 magnesium alloy under lower stress is COBLE creep controlled by grain boundary diffusion of magnesium; however, at higher stress the creep accords with WEETMAN creep controlled by dislocation climb. The creep of AZ31 magnesium alloy is controlled by dislocation glide at temperature ranging from 320-420℃. The critical stress σcr which results in changing from COBLE creep to WEETMAN creep is calculated, the magnitude of σcr and the Nabarro-Peieds stress τp has the relation as follows： σcr≈（2～3）τp.