純Ti/純Al摩擦圧接継手境界部の応力・ひずみ,音速および硬さ分布に関する検討

抄録

In order to clarify the stress/strain distribution across the joint interface of friction weld between pure titanium (Ti) /pure aluminium (Al), the characteristics of the joint interface have been investigated in view of ultrasonic leaky surface acoustic (Rayleigh) wave velocity (V_R) and hardness distributions across it. Especially, one of the first efforts is focused on whether a mechanical scanning acoustic microscope (SAM) can be utilized to measure the V_R distribution across the interface or not. The effect of tensile/compressive strains on V_R of Ti and Al substrates, the relation of crystal direction versus V_R for single crystAl pure Al substrate, and V_R distribution across as-welded and post-weld heat-treated Ti/Al friction joints have been investigated by using a SAM.
As for Ti and Al substrates, all direction (isotropic) V_R (AV_R) decreased when the applied tensile strain increased in elastic deformation region, however, they increased as increasing applied strain in plastic one. Compressive strain slightly affected the change of AV_R versus in both elastic and plastic deformation regions. Uni direction (anisotropic) V_R (UV_R) increased as increasing tensile and compressive strains for Ti substrate. While UV_R of Al substrate decreased with increasing of tensile strain, it increased for compressive strain. There was clear relation between UV_R and crystal direction of single crystal pure Al substrate, and the highest UV_R was obtained at the direction parallel to the most close-packed crystal direction of fcc metal ([101]).
In case of as-welded Ti/Al friction joint, the scatter of AV_R distribution was relatively high overall the measured region, and AV_R of Al substrates adjacent to the joint interface was relatively high. It was thought that this high AV_R was resulted from high plastic strain generated during friction weld operation. The scatter of AV_R distribution was reduced and the high AV_R was not observed when the joint was post-weld heat-treated. While axial direction UV_R of Al substrate adjacent to the joint interface was extremely high in as-welded condition, that of radial direction was not high. Those of Ti side were not high in as-welded joint. The V_R distributions were relatively similar characteristics to hardness and calculated stress/strain distributions.