On the Impact of Second Phase Particles on Twinning in Magnesium Alloys

Abstract

Deformation twinning is an important deformation mode in magnesium alloys. Despite this, little is known on the extent to which the stress for twinning can be altered by a dispersion of second phase particles. The current paper presents a series of findings on the role of differently shaped particles on the characteristics of the twins that form. It is shown that coherent rod shaped particles in Mg-Zn alloys have little obvious effect locally on the twin boundaries but that the twin number density is increased by their presence. Plate particles in a Mg-Al-Zn alloy cause obvious perturbations to the twin interface. Loops of twinning dislocations left around the particles eventually collapse into the particle interface, a phenomenon that is evidently facilitated by stress concentration on leading twin dislocation and stress relaxation in the adjacent material.