Wear behavior of HPT processed UFG AZ31B magnesium alloy

Abstract

Dry sliding wear behavior of ultrafine-grained (UFG) AZ31B magnesium alloy processed by high pressure torsion (HPT) has been investigated against bearing steel ball at room temperature. The HPT process progressed with formation of twins (at number of torsional turns N = 0), subgrains (N = ¼) and high angle boundaries (recrystallized, grain size ∼115±21 nm, at N = 5). With the progression of HPT, hardness of the sample increased and wear rate decreased, involving abrasive, oxidative and adhesive mechanisms in all cases. A distinct feature was formation of lathy strips, whose length increased by as much as ∼1 mm with HPT torsional rotations N = 0 and ¼, but diminished after N = 5 to ∼200 µm. The lengthy lathy strips were due to twins and shear bands (which favours crack propagation path) inside larger grains, but diminished because of very fine grains size.