Chen Shuai, Li Wen-Bin, Wang Xiao-Ming, Yao Wen-Jin, Song Jiu-Peng, Jiang Xiang-Cao, Yan Bin-You
School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
National R&D Center for Tungsten Technology & Xiamen Tungsten Co., Ltd., Xiamen 361006, China.
Materials (Basel). 2021 Aug 26;14(17):4847. doi: 10.3390/ma14174847.
To study the dynamic plastic properties of high-purity molybdenum materials at high temperature and high strain rate, we designed tests to compare the mechanical behaviour of two high-purity molybdenum materials with different purities and two with different processing deformation conditions under dynamic impact compression in the temperature range of 297-1273 K. We analysed the molybdenum materials' sensitivities to the strain-hardening effect, strain rate-strengthening effect, and temperature-softening effect as well as the comprehensive response to the combined effect of the strain rate and temperature, the adiabatic impact process, and the microstructure at high temperature and high strain rate. Furthermore, based on a modified Johnson-Cook constitutive model, we quantitatively analysed the flow stresses in these materials. The calculation results strongly agree with the test results. Our findings indicate that the high-purity molybdenum materials show consistent sensitivity to the combined effect of strain rate and temperature regarding the dynamic plastic properties. The materials with higher purity are less sensitive to the combined effect of the strain rate and temperature, and those with less processing deformation experience more pronounced strain-hardening effects. Under high strain rate at room temperature, these materials are highly susceptible to impact embrittlement and decreases in dynamic plastic properties due to intergranular fracture in the internal microstructure. However, increasing the impact environment temperature can significantly improve their plastic properties. The higher the temperature, the better the plastic properties and the higher the impact toughness.
为了研究高纯钼材料在高温和高应变速率下的动态塑性特性，我们设计了试验，以比较两种不同纯度的高纯钼材料以及两种具有不同加工变形条件的材料在297 - 1273 K温度范围内动态冲击压缩下的力学行为。我们分析了钼材料对应变硬化效应、应变速率强化效应和温度软化效应的敏感性，以及对应变速率和温度综合作用、绝热冲击过程以及高温和高应变速率下微观结构的综合响应。此外，基于修正的Johnson - Cook本构模型，我们定量分析了这些材料中的流动应力。计算结果与试验结果高度吻合。我们的研究结果表明，高纯钼材料在动态塑性特性方面对应变速率和温度的综合作用表现出一致的敏感性。纯度较高的材料对应变速率和温度的综合作用不太敏感，而加工变形较少的材料表现出更明显的应变硬化效应。在室温高应变速率下，这些材料极易因内部微观结构中的沿晶断裂而发生冲击脆化和动态塑性特性下降。然而，提高冲击环境温度可以显著改善它们的塑性特性。温度越高，塑性特性越好，冲击韧性越高。
