Hall–Petch relationship in Ti3Al nano-polycrystalline alloys by molecular dynamics simulation

The Hall–Petch relationship and deformation process in Ti₃Al nano-polycrystalline alloys are investigated using molecular dynamics simulations in this research. The impact of different grain sizes and temperatures on mechanical characteristics was considered. Different Hall–Petch relations were detected for samples with the grain sizes ranging from 2 to 20 nm, inverse Hall–Petch relations in big grain sizes ranges, and positive Hall–Petch relations in the medium grain size region, respectively. A transition zone formed at the interception of positive and inverse Hall–Petch relations, which will vanish as the temperature rises. The critical grain size of the positive Hall–Petch relation decreases as the temperature rises from 10 to 600 K. With the grain size increases in the smaller grain size range, the yield stress increases, which is made by the grain boundary motion and rotation. Besides, temperatures affect mechanical characteristics. The rising temperatures lead to the decreasing dislocation density and a high grain boundary fraction.