MICROSTRUCTURAL FEATURES OF DISSIMILAR MMC AISI-304 STAINLESS-STEEL FRICTION JOINTS/

The microstructure and mechanical properties of dissimilar friction jo ints between aluminium-based MMC and AISI 304 stainless steel base mat erials were investigated. The microstructural features which occur in the stainless steel substrate comprise deformation twinning, formation of a fine-grained dislocation substructure in austenite, and plastic deformation. The stainless steel substrate was plastically deformed in the region close to the mid-radius of the dissimilar joint. In a simi lar manner, 5-10 mu m thick transition layers, comprising regions of l ocally plasticized MMC-base material, were formed close to the mid-rad ius location in dissimilar joints. The interlayer formed at the dissim ilar joint interface comprised a mixture of oxide (Fe(Al,Cr)(2)O-4 or FeO(AI,Cr)(2)O-3) and FeAl3 intermetallic phases. The notch tensile st rength of dissimilar MMC/AISI 304 stainless steel joints increased whe n the rotational speed increased from 500 r.p.m. to 1000 r.p.m., and a t higher rotation speeds, there was no effect on notch tensile strengt h properties.