Evolution of internal stresses during cyclic deformation in LPSO type of magnesium alloy monitored by in-situ neutron diffraction

その場中性子回折によるLPSO型マグネシウム合金の繰返し変形下における内部応力の評価

諸岡 聡  ; Gong, W.*; 相澤 一也  ; 川崎 卓郎   ; Harjo, S.   

Morooka, Satoshi; Gong, W.*; Aizawa, Kazuya; Kawasaki, Takuro; Harjo, S.

Recently, a series of magnesium alloys containing a 18R Long-Period Stacking Ordered (LPSO) structure, have attracted considerable attention because they exhibit excellent mechanical properties, including high strength and reasonable ductility. To determine the plastic deformation behaviour of LPSO structure and the origin of the deformation mechanism are important for further materials development. In this study, deformation-kinking behavior of a MgZnY alloy was investigated by in-situ neutron diffraction during cyclic deformation. In-situ TOF neutron diffraction experiments during tension-compression and compression-tension cyclic loading at room temperature were performed by TAKUMI at MLF of J-PARC. The peak stress in the compression is larger than that of the tension, suggesting that quasi-twinning accompanying with hardening was occurred in compression deformation. On the other hand, results of individual (hkl) lattice strains in the loading direction show that, the (60.0) family grains in the loading direction accommodated a greater portion of elastic strain than that of the (00.18) family grains in the loading direction start accommodated less portion. This indicated that the latter started to yield prior to that of the former, causing the former to carry more applied load, i.e., intergranular stress. The large intergranular stresses generated with the progress of deformation, were speculated to accelerate the backward plastic flow that resulting in an increase of the Bauschinger stress and Bauschinger strain.