Relationship between Deep Drawability and Microstructure of Magnesium Alloy

抄録

Mg–1.5Zr alloy blanks 1.0 mm in thickness, made from cast and rolled materials, were deep-drawn at room temperature and 150°C. The microstructures were examined and deformability evaluated. The grain size of blanks from cast and rolled materials was 40 µm and 15 µm, respectively. The basal texture was confirmed for rolled-blanks, while the microstructures of cast blanks were randomly orientated. The limiting drawing ratio for cast materials was 1.65 at room temperature and 1.75 at 150°C. For rolled-blanks, it was 1.45 and 1.70 at room temperature and 150°C, respectively. The cast-blanks deformed in a similar way at room temperature and at 150°C, exhibiting a decrease in thickness in the punch-shoulder areas and a progressive increase along the side wall toward the rim of the cups. Rolled-blanks tested at 150°C showed the similar trend as cast-blanks and exhibited evidence of dynamic recrystallization in the punch-shoulder areas, contributing to an improvement on the limiting drawing ratio. When the deep-drawing exceeded the limiting drawing ratio, the cast-blanks tested at room temperature and 150°C and also the rolled-banks tested at 150°C fractured in the rim area of the cups, while the rolled-blanks at room temperature fractured from the punch-shoulder areas.

 

This Paper was Originally Published in Japanese in J. JILM 69 (2019) 101–106.

Fig. 15 EBSD image quality (IQ) maps and IPF images (corresponding locations to IQ maps) of the bottom corner (R section) of the cups formed from rolled-blanks at room temperature and 150°C. Red lines in the IQ maps indicate twin crystals. Circled areas in the IPE image (B₁₅₀) suggest the presence of sub-grain and grain boundaries within the crystal.