恒温クロス圧延により微細化されたAZ91マグネシウム合金板材の超塑性挙動(力学特性)

概要

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Thin magnesium alloy sheets of AZ91 by using isothermal cross-rolling have been prepared in present study. These sheets were annealed around the temperature between 0% and 100% recrystallization. X-ray pole figure analysis (XPFA) by Schulz's reflection method was used in order to investigate the texture of annealed sheets. As a result of XPFA, a large anisotropic texture was reduced compared to unidirectional rolled AZ91 sheets. Constant initial strain tensile tests were carried out at elevated temperatures and at several strain-rates. The m value over about 0.3 was observed at testing temperature of 573 to 623K at strain rate of 1.O×10^<-4> to 2.5×10^<-4> s^<-1>, and at testing temperature of 648K at strain rate of 1.0×10^<-3> to 2.5×10^<-3> s^<-1>. The temperature indicated the peak in elongations moved largely to lower temperature region. The activation energy required for superplastic deformation was calculated to be 73-76 kJ・mol^<-1>, which was almost the same value of the activation energy for self-diffusional grain boundary coefficient in magnesium.
2008-06-01