Effects of solute segregation on the mobility and mechanical properties of {10[formula omitted]2} coherent twin boundary in magnesium

Abstract

The effects of solute segregation on the mobility and mechanical properties of {101¯2} coherent twin boundary (CTB) are studied using first-principles calculation methods. 16 alloying elements are chosen to test the effects. The mobility of {101¯2} CTB is limited by the pinning effect led by the solute segregation. The pinning limit is shown to be highly dependent on the solute element segregating at the CTB, and the pinning efficiency is revealed to be only associated with the position that the solute atoms segregate in. Solute segregation affects the toughness and strength of the {101¯2} CTB. Ba and Li are CTB embrittlement elements while Ca, Si, Zn, Al, Ag, La, Ce, Nd, Gd, Tb, Y, Lu, and Zr are CTB toughening elements. Ba, Li, together with Sr, Ca, are found to be CTB weakening elements, and La, Ce, Nd, Al, Zn, Gd, Tb, Y, Lu, Ag, Si, and Zr are CTB strengthening elements. The pinning effect, and the effects on the CTB toughness and strength are relative to the solute segregation propensity in the CTB. Higher segregation propensity at the compression site of {101¯2} CTB is revealed to result in stronger pinning effects, stronger CTB toughening and strengthening effects, while for the segregations at the extension site, the trend is opposite.