【摘要】 运用Prasad失稳准则建立了Mo-Nb单晶材料的加工图,研究了材料在1100¹300℃,应变速率0.001¹0s^-1范围内的热变形特征。结果显示,变形温度和应变速率对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,Mo-Nb单晶的最佳热变形条件为变形温度>1190℃和应变速率>3.16 s^–1。材料的显微组织表明,在1150℃/10s^-1和1100℃/0.01 s^-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℃/0.01 s-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。X射线衍射结果显示,经1300℃/10s^-1变形后的样品仍保持相对较好的单晶组织。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。更多还原

【Abstract】 The processing map of Mo-Nb single crystals was established on the base of Prasad instability. The hot deformation behavior of Mo-Nb single crystals has been characterized through stress-strain curves and processing map in the temperature range of 1100¹300 ℃ and strain rate range of 0.001¹0s^-1. The results indicate that the flow stress is affected significantly by deformation temperature and strain rate during the hot deformation of Mo-Nb single crystals. Based on the processing map, the optimum condition for hot deformation of Mo-Nb single crystals is in the region of high temperatures（>1190 ℃） and high strain rates(>3.16 s^-1). Microstructure observation of deformed specimens at different deforming conditions shows that lots of orthogonal cracks, which result from the movement of dislocations along with the glide planes, are observed in specimens deformed at 1100 ℃/0.01 s^-1 and 1150 ℃/10s^-1. Less cracks can be observed in specimens deformed at 1250 ℃/0.01 s^-1, and few cracks are found in specimens deformed at 1300 ℃/10s^-1. The XRD result shows that the specimen deformed at 1300 ℃/10s^-1 retains single crystal structure, indicating that the specimen does not undergo instability of flow during hot deformation, which are in good agreement with the results of Mo-Nb single crystals predicted from processing map.更多还原