Abstract
Austenitic stainless steels X4CrNi18-12 and X8CrMnNi19-6-3 were processed by accumulative roll bonding (ARB). Both materials show an extremely high yield strength of 1.25 GPa accompanied by a satisfactory elongation to failure of up to 14% and a positive strain rate sensitivity after two ARB cycles. The strain-hardening rate of the austenitic steels reveals a stabilization of the stress-strain behavior during tensile testing. Especially for X8CrMnNi19-6-3, which has an elevated manganese content of 6.7 wt.%, necking is prevented up to comparatively high plastic strains. Microstructural investigations showed that the microstructure is separated into ultrafine-grained channel like areas and relatively larger grains where pronounced nano-twinning and martensite formation is observed.
Highlights
Accumulative roll bonding (ARB) [1] as a process of severe plastic deformation is one of the most effective methods for the production of bulk ultrafine-grained (UFG) materials with a median grain size smaller than 1 μm
While the hardness of X4CrNi18-12 increases rather constantly between one and three cycles, the hardness of X8CrMnNi19-6-3 already appears to saturate after two ARB cycles
Commercially available austenitic steels X4CrNi18-12 and X8CrMnNi19-6-3 were processed by accumulative roll bonding at elevated temperatures
Summary
Accumulative roll bonding (ARB) [1] as a process of severe plastic deformation is one of the most effective methods for the production of bulk ultrafine-grained (UFG) materials with a median grain size smaller than 1 μm. Kitahara et al [13] investigated the martensite transformation of an ultrafine-grained Fe-28.5at.-%Ni-alloy with single phase metastable austenite at room temperature They performed the accumulative roll bonding process with sheets that were pre-heated at 500 °C for 600 s up to 5 cycles. Each cycle was divided into two passes with a thickness reduction
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