Textural and microstructural analyses and ranking of the process parameters in hydro-mechanical deep drawing of AZ31B magnesium sheets

Abstract

The present research work is a comprehensive study on the hydro-mechanical deep drawing (HMDD) process of AZ31B magnesium alloy at elevated temperatures. Several process parameters including the forming temperature, fluid pressure and initial blank diameter were considered to conduct a full factorial experiment. The changes in the thickness strain and thickness variation of the final product were also chosen as the responses. The outcomes gained from the design of experiment technique demonstrated that the initial blank diameter (with 31.3%), process temperature (with 30.2%) and the fluid pressure (with 18.4%) were respectively the most important factors affecting the quality and homogeneity of the AZ31B drawn cup. Moreover, the appropriate process temperature and fluid pressure for HMDD operation of this alloy were, in turn, 200 °C and 15 MPa. Afterwards, a complete texture analysis was carried out and its relation with the hardness distribution in different regions of the workpiece was examined. In addition, the correlation between the microstructures, obtained from the optical microscopy, scanning electron microscopy and X-ray diffraction, with findings of the hardness tests was studied for the optimally produced cup. Based on the textural inspections, it was found that reduction in the basal texture of the flange area in comparison with the bottom of the product was about 12.5%. Moreover, the maximum increase in the hardness (about 24%) and decrease in the average grain size (about 42%) occurred in the wall area of the final product.