The butt dissimilar joints of carbon steel JIS-S45C and die-cast aluminum alloy JIS-ADC12 by means of friction stir welding were prepared for discussing the mechanical properties of the joints. Nanoindenter was used for measuring the converted Vickers hardness distribution and the elastic modulus distribution of ADC12 around the welding interface. From the experimental results, it was found that there is lower hardness region where distance from the interface is less than approximately 10mm. And around the region where the distance is about 12mm, the hardness indicated minimum value of 90 Hv*. On the other hands, in case of distribution of the elastic modulus, there was less correlation with distribution of the hardness. The values of elastic modulus was approximately 95GPa in the region where distance from the interface is less than approximately 15mm, and it was about 85GPa in the region of base metal. Further, it was found that the hardness of the Si particles in ADC12 was about 1100 Hv* which was order of magnitude compared with the hardness of Al region
YAMAMOTO et al. (Wed,) studied this question.