The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced ...The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced microstructure evolution and related mechanical property of Fe52−xMn27Cr15Co6Six(x=0,0.3,0.5,1.0,1.5,at.%)HEAs was systematically investigated by utilizing the in-depth microstructural characterization coupled with X-ray diffractometer(XRD),secondary electron microscopy(SEM),and transmission electron microscopy(TEM).The addition of Si to Fe52−xMn27Cr15Co6Six HEAs facilitates the triplex structure consisting of fcc-γmatrix,thermally-inducedε-martensite and sigma phase(σ).The lattice distortion energy by Si atoms is suggested to promote the formation ofσphase consisting of Cr,Si and Co and consequently influence the metastability of the matrix.In 0.3 at.%Si HEA,the strain-induced bodycentered tetragonal(bct)-typeα’-martensite were observed at the intersection of bi-directional straininducedε-martensite laths,enhancing the ultimate tensile strength to∼851 MPa from∼618.3 MPa with ductility increment(∼73.1%from∼71%).In 0.3 at.%Si and 0.5 at.%Si alloys,the granular-typeσphase was observed both at grain boundaries and in grain interior,and the size of granular-typeσphase at grain boundary and intra-granularσphase were found to be similar.The deformation mode altered from the transformation-induced plasticity(TRIP)to twinning-induced plasticity(TWIP)with an increase of Si content to 1.5 at.%,due to the enhanced fcc-γstability induced by the compositional modulation driven by increasedσphase formation.The propagation of microcracks inside brittleσphase could be suppressed by homogeneous slip through strain-induced martensite transformation(SIMT)in HEAs with low Si addition of 0.3at.%-0.5 at.%.展开更多
基金financially supported by the National Research Foundation of Korea(NRF)grants funded by the Korean Govern-ment(Nos.RS-2023-00281246 and RS-2024-00398068)the grant(No.360-05-01-PNK9690)by the Department of Hydrogen Materials Evaluation at Korea Institute of Materials Science(KIMS).
文摘The phase metastability and precipitation are now considered to be an important strategy in designing Fe-rich high entropy alloys(HEAs).In this study,the influence of silicon addition on the initial and straininduced microstructure evolution and related mechanical property of Fe52−xMn27Cr15Co6Six(x=0,0.3,0.5,1.0,1.5,at.%)HEAs was systematically investigated by utilizing the in-depth microstructural characterization coupled with X-ray diffractometer(XRD),secondary electron microscopy(SEM),and transmission electron microscopy(TEM).The addition of Si to Fe52−xMn27Cr15Co6Six HEAs facilitates the triplex structure consisting of fcc-γmatrix,thermally-inducedε-martensite and sigma phase(σ).The lattice distortion energy by Si atoms is suggested to promote the formation ofσphase consisting of Cr,Si and Co and consequently influence the metastability of the matrix.In 0.3 at.%Si HEA,the strain-induced bodycentered tetragonal(bct)-typeα’-martensite were observed at the intersection of bi-directional straininducedε-martensite laths,enhancing the ultimate tensile strength to∼851 MPa from∼618.3 MPa with ductility increment(∼73.1%from∼71%).In 0.3 at.%Si and 0.5 at.%Si alloys,the granular-typeσphase was observed both at grain boundaries and in grain interior,and the size of granular-typeσphase at grain boundary and intra-granularσphase were found to be similar.The deformation mode altered from the transformation-induced plasticity(TRIP)to twinning-induced plasticity(TWIP)with an increase of Si content to 1.5 at.%,due to the enhanced fcc-γstability induced by the compositional modulation driven by increasedσphase formation.The propagation of microcracks inside brittleσphase could be suppressed by homogeneous slip through strain-induced martensite transformation(SIMT)in HEAs with low Si addition of 0.3at.%-0.5 at.%.
