Effect of grooved roll profiles on microstructure evolutions of AZ31 sheets in Periodical Straining Rolling process

Magnesium alloy sheets have very attractive features such as lightweight, high specific strength, vibration absorption and high electromagnetic shielding although it is well known that the strong (0001) basal texture of magnesium alloy sheets limits the plastic formability at room temperature. Therefore, texture and microstructure control of magnesium alloys are of importance for improvement of sheet formability. Many processes for controlling microstructures have been proposed and their effectiveness has been discussed. The authors have already proposed the novel rolling process called “Periodical Straining Rolling” or in a short, PSR process that employs the pinion-like or worm-gear-like grooved roll to introduce periodically localized plastic strain in rolled sheet. This process is aimed to control strain distribution to generate microstructure and texture gradient by adapting the proposed process to the conventional strip rolling process. The hot rolling experiment of AZ31 magnesium alloy sheet was conducted with sine curve grooved and continuous arc curve grooved platens to examine the feasibility of the proposed process. As a result, the apparent texture gradients in both the longitudinal and thickness directions are observed from as-PSR processed sheets so that it is proved that the PSR process is able to weaken the (0001) basal texture and increase microstructure evolution of AZ31 sheets. The optimal roll profile for PSR process is also discussed, being compared with microstructure and crystallographic changes and strain distribution/material flow analysis by rigid plastic FEM simulation.