銅合金に残留する三次元的応力の評価

抄録

It is required that polycrystalline copper alloys used for electronic components reveal good mechanical and electrical properties. For example, high stress relaxation characteristics are required in copper alloys used for connecter terminals. However, residual stresses which are related to stress relaxation characteristics are unclear in those alloys. In order to analyze the residual stresses of polycrystalline materials, the 2D method is useful, since it provides the three–dimensional stress tensor in microscopic area. Residual stress characteristics in Cu–Mg alloys heat–treated at 250°C, 300°C, and 350°C and deformed in tensile machine at speed of 0.1 mm/min were investigated in this study, to reveal the mechanism of stress relaxation of heat treatment and stress inducement by elongation. And stress ellipsoid was calculated by stress tensor. It indicates the magnitudes, direction, and tensile or compression of principal stresses, and it can evaluate the contribution of shear stress. Normal stress and principal stress are nearly equal values and directions in all samples. It indicates tensile stress by tensile machine affect normal stress directly, and contribution of shear stress is small. So, tensile deformation of crystal lattice is mainly occurred, effect of shear deformation is small. Also, as the temperature of heat treatment is higher, normal stress, its direction is equal to tensile direction, is increased. As higher heat treatment temperature is effective to stress relaxation, the interaction of residual stress and tensile stress is small. These results reflect the change of stress field in measurement area. And results of re–measured residual stress in all samples reproductively were obtained.