THE MICROSTRUCTURAL, MECHANICAL, AND FRACTURE PROPERTIES OFAUSTENITIC STAINLESS STEEL ALLOYED WITH GALLIUM

摘要

Diffusion of Ga into austenitic stainless steel storage containers housing plutonium-galliumcompounds is likely during fifty-year storage at temperatures as high as 250℃. Thus, the mechanicarand fracture properties of austenitic stainless steels alloyed with gallium require assessment in order todetermine the likelihood of premature failure following Ga uptake. AISI 304 L SS (UNS $30403) wascast with 1, 3, and 12 wt % Ga. Increased Ga concentration promoted duplex microstructure formationwith the ferritic phase having a nearly identical composition to the austenitic phase. Room temperaturetests indicated that small additions of Ga (less than 3 wt%) were beneficial to the mechanical behaviorof 304 L SS but that 12 wt% Ga resulted in a 95% loss in ductility. Small additions of Ga are beneficialto the cracking resistance of stainless steel also. 3 wt% Ga alloys showed the greatest resistance to crackinitiation and propagation as measured by fatigue crack growth rate, fracture toughness, and tearingmodulus. 12 wt% Ga alloys were least resistant to crack initiation and propagation and these alloysfailed by transgranular cleavage. It is hypothesized that the embrittlement is attributable to composition(I.e., Ga in solid solution) and not microstructure (I.e., the presence of ferrite), per se.