Prasad Mahesh R G, Neogi Anupam, Vajragupta Napat, Janisch Rebecca, Hartmaier Alexander
Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universität Bochum, 44801 Bochum, Germany.
Materials (Basel). 2021 May 2;14(9):2369. doi: 10.3390/ma14092369.
Employing atomistic simulations, we investigated the void collapse mechanisms in single crystal Ni during hydrostatic compression and explored how the atomistic mechanisms of void collapse are influenced by temperature. Our results suggest that the emission and associated mutual interactions of dislocation loops around the void is the primary mechanism of void collapse, irrespective of the temperature. The rate of void collapse is almost insensitive to the temperature, and the process is not thermally activated until a high temperature (∼1200-1500 K) is reached. Our simulations reveal that, at elevated temperatures, dislocation motion is assisted by vacancy diffusion and consequently the void is observed to collapse continuously without showing appreciable strain hardening around it. In contrast, at low and ambient temperatures (1 and 300 K), void collapse is delayed after an initial stage of closure due to significant strain hardening around the void. Furthermore, we observe that the dislocation network produced during void collapse remains the sample even after complete void collapse, as was observed in a recent experiment of nickel-base superalloy after hot isostatic pressing.
通过原子模拟，我们研究了单晶镍在静水压力压缩过程中的空洞坍塌机制，并探讨了空洞坍塌的原子机制如何受温度影响。我们的结果表明，无论温度如何，空洞周围位错环的发射及相关的相互作用是空洞坍塌的主要机制。空洞坍塌速率几乎对温度不敏感，直到达到高温（约1200 - 1500 K）时该过程才会被热激活。我们的模拟表明，在高温下，位错运动由空位扩散辅助，因此观察到空洞持续坍塌，且其周围未出现明显的应变硬化。相比之下，在低温和环境温度（1和300 K）下，由于空洞周围显著的应变硬化，空洞坍塌在初始闭合阶段后会延迟。此外，我们观察到，正如最近在镍基高温合金热等静压实验中所观察到的那样，即使在空洞完全坍塌后，空洞坍塌过程中产生的位错网络仍保留在样品中。
