高温变形能建模及其在Mg−Li−Al−Y合金中的应用

摘要

为了控制超塑性流动和断裂并研究变形能的变化,采用拉伸实验和显微组织定量方法获得Mg?7.28Li?2.19Al?0.091Y合金的应力和晶粒尺寸并建立新的高温变形能模型.结果表明,晶粒内部变形能随应变速率增大而增大,随温度升高而降低;晶界变形能的变化与晶粒内部变形能的变化相反.在给定温度下,临界空洞形核能随应变速率增大而降低,使空洞形核变得容易;在给定应变速率下,临界空洞形核能随变形温度升高而增大,导致空洞形核变得困难.新建立的临界空洞形核半径和能量模型为预测微裂纹的产生和提高成形零件的使用寿命提供了一个新途径.%To control the superplastic flow and fracture and examine the variation in deformation energy, the stress and grain size of Mg?7.28Li?2.19Al?0.091Y alloy were obtained using tensile testing and microstructure quantification, and new high temperature deformation energy models were established. Results show that the grain interior deformation energy increases with increasing the strain rate and decreases with increasing the temperature. The variation in the grain boundary deformation energy is opposite to that in the grain interior deformation energy. At a given temperature, critical cavity nucleation energy decreases with increasing strain rate and cavity nucleation becomes easy, whereas at a given strain rate, critical cavity nucleation energy increases with increasing temperature and cavity nucleation becomes difficult. The newly established models of the critical cavity nucleation radius and energy provide a way for predicting the initiation of microcrack and improving the service life of the forming parts.