High Temperature Deformation Mechanisms and Processing Map for Hot Working of Cast-Homogenized Mg-3Sn-2Ca Alloy

Abstract:

The hot working behavior of Mg-3Sn-2Ca alloy has been investigated in the temperature range 300–500 oC and strain rate range 0.0003–10 s-1, with a view to evaluate the mechanisms and optimum parameters of hot working. For this purpose, a processing map has been developed on the basis of the flow stress data obtained from compression tests. The stress-strain curves exhibited steady state behavior at strain rates lower than 0.01 s-1 and at temperatures higher than 350 oC and flow softening occurred at higher strain rates. The processing map exhibited two dynamic recrystallization domains in the temperature and strain rate ranges: (1) 300–420 oC and 0.0003–0.003 s-1, and (2) 420–500 oC and 0.003–1.0 s-1, the latter one being useful for commercial hot working. Kinetic analysis yielded apparent activation energy values of 161 and 175 kJ/mole in domains (1) and (2) respectively. These values are higher than that for self-diffusion in magnesium suggesting that the large volume fraction of intermetallic particles CaMgSn present in the matrix generates considerable back stress. The processing map reveals a wide regime of flow instability which gets reduced with increase in temperature or decrease in strain rate.

• Periodical: Materials Science Forum (Volumes 638-642)
• Pages: 3616-3621
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.638-642.3616
• Online since: January 2010
• Authors: Kamineni Pitcheswara Rao, Yellapregada Venkata Rama Krishna Prasad, Norbert Hort, Karl Ulrich Kainer
• Keywords: Dynamic Recrystallization (DRX), Hot Workability, Kinetic Analysis, Mg-Sn-Ca Alloy, Processing Map

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DOI: 10.1016/j.intermet.2007.10.011