Abstract:
Embrittlement of an Fe-8% Mn alloy on tempering in the range 300C to 650C has been studied by tensile ductility tests at-78C. Hardness changes and the formation of reverted austenile and epsilon tensite were also monitored during tempering. Hardness increased only slightly during the embrittlement and epsilon tensited did not form until after appreciable times. On quenching from the austenitising temperature a duclitle/brittle transition temperature of + 115C was observed with brittle intergranular failure along prior austenile grain boundaries. No segregation of any of the classical temper embrittling impurities (Sb, Sn, P or As) was observed by Auger Electron Spectroscopy at the prior austenite grain boundaries & in addition, no enhancement of the Mn concentrations was noted. However, N was present on the intergranular facets and ion bombardment revealed a desegregation of C in the vacinity of the boundary. On ageing at 450C a repid grain boundary segregation of Mn and P was noted, with the Mn concentration at the grain boundary approaching its equilibrium value. A kinetic analysis of the segregation showed that the rates were consistent with the bulk lattice diffusion of Mn and P in ferrits. A thermal cycling treatment was developed which lowered the impact transition temperature from + 115C to -60C in this alloy. Apart from grain refinement, evidence is presented to show that deformation induced transformation also occurred on tensile testing to improve toughness.
Page(s):
37-47
DOI:
DOI not available
Published:
Journal: Pakistan Steel Journal, Volume: 37, Issue: , Year: 1989