Abstract
Characteristic microstructure was formed in a low-alloy steel / Ni-base alloy welded interface region by solidification and thermal history. At welding, molten Ni-base alloy solidified epitaxially from low-alloy austenite grains in the beginning. However, the crystal growth often stopped at the place where concentrations of alloy elements changed rapidly. As a result, characteristic grain boundaries parallel to the interface were generated. During cooling after welding, a low-alloy steel region within one individual austenite grain transformed to martensite partially. Hence, the KS relationship was confirmed in such a grain, and the quenched martensite was tempered by the following heating.
