SOLIDIFICATION MICROSTRUCTURE AND CREEP-RUPTURE BEHAVIOR OF ELECTRON-BEAM WELDED AUSTENITIC FE-28MN-6AL-1C ALLOY

Austenitic Fe-28Mn-6Al-1C alloy was welded using the electron beam (EB ) welding technique. After EB welding, fully austenitic microstructure was observed in the weld. Moreover, the entire weld consisted mainly of columnar dendrites with a preferred orientation. The growth and con vergence of these columnar dendrites led to the formation of an appare nt 'parting' in the weld centreline. The parting exhibited a lower har dness value while a peak hardness was observed in the heat affected zo ne (HAZ) of the weld. The higher hardness value in the HAZ was associa ted with the strain induced twinning caused by EB welding. Creep ruptu re tests of the weldment and the base metal were conducted at 873 K ov er a stress range of 225-350 MPa. Creep fracture of the weldments was observed to occur in the region of the parting. The rupture life and r upture ductility of the weldments were considerably lower than those o f the base metal. (C) 1997 The Institute of Materials.