Effect of dimple patterning conditions of Periodical Straining Rolling on microstructures and mechanical properties of AZ31 sheets

Magnesium alloys are well-known for the attractive physical properties such as the lowest density among the structural metallic materials, high specific strength, high vibration absorption and so on. However, the strong (0001) basal texture of wrought magnesium alloys causes the poor plastic formability at room temperature in spite of high Lankford value. Texture and microstructure control of magnesium alloys are quite necessary to improve the cold sheet formability in order to prevail the wider application of wrought magnesium alloy products. The authors have already proposed the novel rolling process called "Periodical Straining Rolling (PSR)" using the small grooved roll to introduce periodically localized plastic strain in rolled sheet and confirmed that its effectiveness of the proposed rolling can realize the micro texture and microstructure control. This paper is aimed to discuss the effects of control of spatial strain distribution on microstructure, micro texture and mechanical properties by using various dimple patterning conditions of PSR process. The microstructure and micro texture observations of AZ31 magnesium alloy sheets PSR processed under the several dimple patterning conditions (two-sided PSR processing conditions) evince that the weak crystallographic orientations are largely prominent by changing dimple patterning conditions. As a result, the higher Erichsen values can be effectively achieved by changes in dimple patterning as compared to the conventional flat rolling process.