单晶钛变形机制的分子动力学研究

Molecular dynamics study of the deformation mechanism of single-crystal titanium

摘要:

本研究采用分子动力学模拟方法研究了单晶钛的变形机制，研究温度为500~1000K，应变率为"0.0001" 〖"ps" 〗^"-1" ~"0.01" 〖"ps" 〗^"-1" ，加载方式为拉伸和压缩，对结果进行了应力应变分析、势能分析、共进邻分析和位错密度分析。结果表明，随温度的升高，屈服强度降低，屈服点对应的应变值减小；在相同温度下，拉伸屈服强度略高于压缩屈服强度；不同加载速率下弹性模量变化不大，加载速率增加屈服强度增大。随温度的升高或加载速率增加，体系的势能峰值增加。随着应变的进行，HCP结构减少，Other结构增加，BCC、FCC结构出现并增加（除变形温度1000K时以外）；超过屈服点后，各种结构逐渐趋于平稳；随着温度的升高，晶体结构的转变提前发生。随着温度的升高，位错密度降低，拉伸载荷下的总位错密度大于压缩载荷；整个变形过程中的主要位错类型是Other位错、1/3<-1100>位错和1/3<11-20>位错。

Abstract:

In this study, the deformation mechanism of single-crystal titanium was investigated by molecular dynamics simulation, the temperature was 500~1000K, the strain rate was "0.0001" 〖"ps" 〗^"-1" ~"0.01" 〖"ps" 〗^"-1" , and the loading mode was tensile and compressive, and the results were subjected to the stress-strain analysis, potential analysis, coevolutionary neighbourhood analysis and dislocation density analysis. The results show that with the increase of temperature, the yield strength decreases, and the strain value corresponding to the yield point decreases; at the same temperature, the tensile yield strength is slightly higher than the compressive yield strength; the modulus of elasticity does not change much under different loading rates, and the yield strength increases with the increase of loading rate. With the increase of temperature or loading rate, the peak potential energy of the system increases. As the strain proceeds, the HCP structure decreases, the Other structure increases, and the BCC and FCC structures appear and increase (except at the deformation temperature of 1000K); after exceeding the yield point, the various structures gradually tend to stabilise; with the increase of temperature, the transformation of crystal structure occurs earlier. The dislocation density decreases with increasing temperature, and the total dislocation density under tensile load is larger than that under compressive load; The main types of dislocations throughout the deformation process are Other dislocations, 1/3<-1100>dislocations and 1/3<11-20> dislocations.