Hot deformation behavior of Mg_2B_2O_5 whiskers reinforced AZ31B magnesium composite fabricated by stir-casting

摘要

The hot deformation behavior of Mg_2B_2O_5w/AZ31B composite was investigated by compression test at temperatures between 473 K and 673 K with the strain rates from 10~(-4)s~(-1) to 1 s~(-1). The constitutive equations were established by taking peak stresses as the function of temperatures and strain rates. It was found that the function of exponential and power law creep equations broke down at low and high stresses for the composite, respectively. The hyperbolic sine law creep equation was in good agreement with experimental results and can be applied to all flow stresses under the various deformation conditions. The composite possesses slightly higher activation energy values than that of lattice self-diffusion of pure Mg, and the stress exponent was calculated to be about 6.6. The plastic deformation mechanism of the composites at high temperature was mainly through the lattice diffusion controlled dislocation climb. Dynamic recrystallization took place during hot compression, and grains became coarser at lower strain rate and higher temperature.