Mechanical and microstructural evolution of Mg AZ31 alloy using ECASD process

Abstract

A continuous severe plastic deformation (SPD) technique called equal-channel angular sheet drawing (ECASD) was used to mechanically deform an annealed magnesium AZ31B alloy. Samples of 2.45mm thickness by 50mm width and 200mm in length were cut from a sheet and then submitted to two different ECASD routes: route A: the sample is not rotated around its axis and, route C: the sample is rotated 180° around its axis between passes. The samples were held up to six ECASD passes at room temperature (RT). The processing speed was set at 20mm/min for both routes. The mechanical properties and the micro-structural evolution were studied as a function of the number of passes, and processing route; tensile and hardness tests were used for this purpose. A grain size refinement is achieved from the first pass for both routes, being the grain refinement more marked for route A; at the last passes is evident the presence of twins. Hardness had shown a remarkable increase in each pass. It was found that the route C produces better uniform hardness distribution through the thickness of the samples when is compared with route A. Nevertheless, ultimate tensile strength (UTS) and yield strength (YS) are inconsistent with the Hall–Petch relationship. It could be due to a higher rate of texture softening verses the strengthening effects of the grain refinement.