Molecular dynamics study of melting initiation at tilt grain boundaries depending on their misorientation angle in aluminum

Abstract The influence of the misorientation angle and the energy of tilt grain boundaries with misorientation axes <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈" separators=""> <mml:mrow> <mml:mn>100</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈" separators=""> <mml:mrow> <mml:mn>110</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈" separators=""> <mml:mrow> <mml:mn>111</mml:mn> </mml:mrow> </mml:mfenced> </mml:math> on the melting temperature and the nature of the initiation of melting at the grain boundaries in aluminum with nanosized grains was studied using molecular dynamics simulation. It was shown that with heating at a constant rate, melting begins from the grain boundaries, where there is a violation of the crystal structure and, accordingly, the atoms are in shallower potential wells. In the case of high-angle boundaries, melting began simultaneously along the entire boundary, while for low-angle boundaries, it initiated at the cores of the grain boundary dislocations. In the range of small misorientation angles (less than 15°), the melting temperature of the modeled aluminum computational cell decreases almost linearly with increasing the misorientation angle; then, for high-angle boundaries, the decrease becomes less intense. These dependencies correlate with the energy of grain boundary formation or with the associated value of excess energy of the computational cell. It was shown that the melting temperature decreases linearly with the growth of excess energy, that is, the difference in the energies of the considered structure of the computational cell containing the grain boundary and the ideal crystal.