Defects induced through rapid solidification in a Co-20 Cr alloy

Martensitic transformation in cobalt alloys has been widely explored due to its complex nature. Recent studies demonstrated that rapid solidification enhances the gamma-FCC-epsilon-HCP transformation through a high density of epsilon-martensite nucleating defects formation (i. e. vacancy supersaturation, sub - micron sized voids, staking faults/epsilon - martensite plate intersections, among others), resulting in almost 100% epsilon-martensite. In this work, the rapid solidified (RS) alloy exhibits a complex microstructure consisting of an athermal epsilon-martensite matrix with residual austenite (gamma-phase) as the gamma -> epsilon transformation was kinetically dominant. Thus, a variety of defects are exposed, and critical theoretical modeling is derived from TEM experimental evidence, consequently, their interactions as a stair-rod dislocations are proposed. A disclosure concerning how these defects' interaction influence the mechanical behavior of the studied Co-20 Cr alloy in the as - cast and heat - treated (at 1023 K/750 C for 1 h) conditions is presented. In particular, annealing was found to be highly effective in promoting alloy strength and ductility. Apparently, internally straining is considerably reduced through thermally activated recovery mechanisms including epsilon-plate thickening and alloy recrystallization.