Mo-Nb单晶材料的热变形行为及加工图

Hot Deformation Behavior and Processing Map of Mo-Nb Single Crystals

摘要:

运用加工图以及Prasad失稳准则研究了Mo-Nb单晶材料在1100-1300℃，变形速率0.001-10s-1范围内的热变形特征。结果显示，变形温度和变形速率对Mo-Nb单晶材料的流变应力有着显著的影响。材料的加工图表明，在相对较高的变形温度（>1190℃）和应变速率条件下（>3.16s-1)，变形后的样品仍然可以保持相对较好的单晶组织结构。材料的显微组织表明，在1150℃/10s-1和1200℃/0.01s-1变形条件下，变形后的样品内部出现了大量的裂纹，且裂纹区域面积较大，经1250℃/1s-1变形的样品，内部只有局部位置出现少量裂纹，1300℃/10s-1变形的样品内部未发现明显的裂纹，XRD衍射结果显示，经1300℃/10s-1变形后的样品仍保持相对较好的单晶组织。实验结果表明，在1300℃/10s-1变形条件下，样品在变形过程中没有发生变形失稳，这与采用加工图预测的结果相符。

Abstract:

The hot deformation behavior of Mo-Nb single crystals has been characterized through strain-stress curves and processing map in the temperature range of 1100-1300℃ and strain rates range of 0.001-10 s-1. The results indicate that the flow stress was affected significantly by deformation temperature and strain rate during the hot deformation of Mo-Nb single crystals. Base on the processing map, the optimum condition for hot deformation of Mo-Nb single crystals is the region of high temperatures (>1190℃) and high strain rates (>3.16s-1). Through observation of microstructure of deformed specimens at different deforming conditions, lots of orthogonal cracks, which result from the movement of dislocations along with the glide planes, were observed in specimens deformed at 1100℃/0.01s-1 and 1150℃/10s-1. Less cracks can be observed in specimens deformed at 1250℃/0.01s-1, and few cracks were found in specimens deformed at 1300℃/10s-1. The XRD result shows that the specimen deformed at 1300℃/10s-1 still retains single crystal structure, indicating that the specimen was not undergone instability of flow during hot deformation at the deformation condition of 1300℃/10s-1, which are in good agreement with the results of Mo-Nb single crystals predicted from processing map.