Asahi Nomoto 1, Sakiko Kashiwase 1, Kyosuke Nakagawa 1, Hiromu Hisazawa 2 and Yoshihiro Terada 1
1 Department of Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology
Age-hardening behavior of a Mg-4.98Al-1.46Ca (mass%) die-cast alloy was investigated at the temperature range between 473 and 623 K. Transmission electron microscopy shows that fine C15-Al2Ca precipitates with a disc-shaped morphology are placed on the (0001) basal plane of the α-Mg matrix phase at the 523 K/10 h peak-aged condition, while they coarsen at the 623 K/100 h over-aged condition. The ultimate tensile strength of the peak-aged alloy is usually higher than that of the over-aged alloy for approximately 40 MPa at both 298 and 473 K, indicating that the precipitation strengthening by fine C15-Al2Ca precipitates is operative even at high temperatures. Dislocations are introduced within the α-Mg matrix phase of the alloy during die-casting; the dislocations are mostly a type and the dislocation segments are mainly located on the (0001) basal plane. The interrelation between fine C15-Al2Ca precipitates and dislocations during tensile deformation is discussed based on the results of tensile tests.
magnesium alloy, age-hardening, Laves phase, tensile strength, dislocation
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