Carbide effects on tensile deformation behavior of [001] symmetric tilt grain boundaries in bcc Fe

Abstract

The mechanical performance of carbides on the grain boundary (GB) of ferritic steels is always concerned. In this paper, four symmetric tilt GBs in body-centered cubic Fe were studied under tensile tests at 0 and 300 K through atomistic simulations. The GBs contained various sized Cr23C6 precipitates. Stress-strain curves were obtained through the molecular dynamics simulations and the tensile strength varied with GB type. Centro-symmetry parameter, common neighbor and dislocation analyses were performed for defect characterization. GBs with precipitates showed lower tensile strength than pure GBs. As the number and size of carbides increased, the tensile strength decreased. Cavities were easily formed near dislocation loops with a Burgers vector parallel with loading direction during tensile deformation of pure GBs, while ruptures occurred around the precipitate in GBs with carbides. The simulations indicate that Cr23C6 carbides in Fe are a brittle phase where the dislocations and cracks nucleate.