Al-Mg合金中锯齿形屈服现象的热分析

研究了在室温、定加载应变率拉伸的情况下Al-Mg合金中的锯齿形屈服现象.伴随着锯齿形屈服现象的发生,试件表面温度场会发生变化.而红外相机能以较高的时间、空间分辨率记录下随时间变化的试件表面温度场图像.通过分析这些热图像,探讨了A,B两种类型带的传播规律,得到了局域变形带的带宽、倾角、传播速度等特征参数.在此基础上,引入热传导方程,求得了带内的应变率.实验和计算都发现B类型带产生时试件表面带外区域存在弹性收缩现象,由此提出以是否存在带外收缩变形作为划分A,B类型带的新标准.

Thermal analysis of serrated yielding in an Al-Mg alloy

The serrated yielding phenomenon is studied in an Al-Mg alloy during the tensile tests at ambient temperature and constant strain rate. The temperature field on the surface of the specimen changes with the increase of strain. An infrared camera is used to observe and record the temperature variations at very high time and space resolutions. According to these thermal data, the formation and propagation of the deformation bands (type A, B) are discussed and some characteristic parameters of the bands such as orientation, bandwidth, and apparent velocity are also obtained. Furthermore, the plastic deformation in the band is quantified from heat transfer equation. Both experimental and computational results show that elastic shrinkage deformation exists outside the band only during the formation of the type B band. Based on this, whether or not shrinkage deformation exists outside the band is proposed as a new standard to discriminate type A and B bands.