AZ91マグネシウム合金の破壊靭性値に及ぼすミクロ組織の影響

概要

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The effect of grain size on mechanical properties of a T6-treated AZ91-magnesium alloy was studied. In order to obtain samples free from shrinkage, oxides and gas defects, the alloy was produced using a continuous casting process with various casting temperatures, and a constant cooling rate. In the T6-treated AZ91 alloy, discontinuous precipitates were observed clearly along small grain boundaries, while continuous precipitates were observed in large grains. It was found that hardness in a grain depended on the form of precipitation and the magnesium alloy having a smaller grain size showed larger values of fracture toughness, ultimate tensile strength, 0.2% proof stress and elongation at fracture. Fracture toughness of the alloy having a finer grain size increased from 18.3 MPa・m^<1/2> to 21.4 MPa・m^<1/2> after T6 treatment. The strengthening mechanisms leading to these results are concluded to be the grain-size dependence of stress concentration at the grain boundary, the density of grain boundaries and the grain boundary precipitates which act as obstacles when cracks propagate.
一般社団法人日本機械学会の論文
1996-08-25