変形双晶を援用したAZ31マグネシウム合金円管局所領域の力学的特性制御の試み

摘要

The objective of this study is to control the local mechanical characteristics of the magnesium alloy circular tube. We focuse to the extension twinning that is activated during plastic deformation. The bulging process was first performed on the selected area of AZ31 magnesium alloy thin-walled circular tube. Next, the additional process was applied to the bulged area to restore the original profile, finally, the work hardening due to processing was removed bv the annealing process. It was found that the processed area exhibited larger flow stress and superior ductility compared with the non-processed area. Vickers hardness test was also conducted and it was revealed that the processed area became harder than the non-processed area. Those results imply the possibility to control the mechanical properties of the selected area of AZ31 magnesium alloy tube by the processes utilized in this study.%実用金属中で最軽量であるマグネシウム合金は，比強度，リサイクル性，振動吸収性などに優れており，省エネルギー化への要求に伴い，様々な産業分野への適用が期待されている.しかし，マグネシウム合金は最密六方結晶構造であるため室温で活動可能なすべり系が限定され，延性に乏しい.また，変形双晶が活動しやすいことから，素材製造時に集合組織を形成し，塑性異方性が成長する.このような背景からマグネシウム合金については，合金元素添加によって集合組織の弱化を目指す研究が多く行われている.それに対して，マグネシウム合金における変形双晶を領域選択的に発生させることができれば，その領域の降伏応力を変化させることが可能になると期待される.