The micro-cracking behaviors of two high-entropy alloys(HEAs) of the FeMnCoCrNi family prepared by selective laser melting were systematically studied. Residual stresses were also analyzed by X-ray diffraction techniq...The micro-cracking behaviors of two high-entropy alloys(HEAs) of the FeMnCoCrNi family prepared by selective laser melting were systematically studied. Residual stresses were also analyzed by X-ray diffraction technique. Results show that the equiatomic FeMnCoCrNi HEAs with a relatively stable single-phase face-centered cubic(FCC) structure suffered from micro-cracking with residual tensile stress after laser melting. In contrast, the metastable non-equiatomic Fe MnCoCr HEAs with reduced stacking fault energy are free of micro-cracks with residual compressive stress at various volumetric energy densities(VEDs). The displacive transformation from the FCC matrix to the hexagonal close-packed(HCP) phase during cooling prevents the micro-cracking via consuming thermal stress related internal energy. Further, the displacive transformation during tensile deformation contributes to the higher strength and ductility of the metastable dual-phase HEA compared to that of the stable single-phase HEA. These findings provide useful guidance for the design of strong, ductile, and crack-free alloys for additive manufacturing by tuning phase stability.展开更多
Thermal-induced transformation of wetting behaviors on laser-textured silicon carbide （SIC） surfaces was discussed in this work. To investigate the transformation, a quenching experiment was conducted and an X-ray d...Thermal-induced transformation of wetting behaviors on laser-textured silicon carbide （SIC） surfaces was discussed in this work. To investigate the transformation, a quenching experiment was conducted and an X-ray diffractometer was used to measure the residual stress. The experimental results demonstrate that the significantly enhanced hydrophilicity was induced by the increasing thermal residual stress of SiC materials after the aqueous quenching. It was found that the decrease in the contact angle increased with the increasing quenching temperature. Quenching at 350℃ led to the change of contact angle from 89.28° to 70.88° for the smooth surface, while from 72.25° to 33.75° for the laser-textured surface with depth 8 μm. Further, the surface hydrophobicity was enhanced by the release of thermal residual stress after quenching, thereby leading to an increase in the contact angle over time. The transformation of wetting behaviors on laser textured SiC surfaces can be achieved mutually by the aqueous quenching method.展开更多
基金financial support of the National Natural Science Foundation of China (51505166,51971248)the Huxiang Young Talents Project (2018RS3007,2019RS1001)+1 种基金the Innovation-Driven Project of Central South University,China (2020CX023)Science and Technology Project of Hunan Province (2020GK2031)。
文摘The micro-cracking behaviors of two high-entropy alloys(HEAs) of the FeMnCoCrNi family prepared by selective laser melting were systematically studied. Residual stresses were also analyzed by X-ray diffraction technique. Results show that the equiatomic FeMnCoCrNi HEAs with a relatively stable single-phase face-centered cubic(FCC) structure suffered from micro-cracking with residual tensile stress after laser melting. In contrast, the metastable non-equiatomic Fe MnCoCr HEAs with reduced stacking fault energy are free of micro-cracks with residual compressive stress at various volumetric energy densities(VEDs). The displacive transformation from the FCC matrix to the hexagonal close-packed(HCP) phase during cooling prevents the micro-cracking via consuming thermal stress related internal energy. Further, the displacive transformation during tensile deformation contributes to the higher strength and ductility of the metastable dual-phase HEA compared to that of the stable single-phase HEA. These findings provide useful guidance for the design of strong, ductile, and crack-free alloys for additive manufacturing by tuning phase stability.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR14E050001)the National Natural Science Foundation of China(Grant No.51275473)
文摘Thermal-induced transformation of wetting behaviors on laser-textured silicon carbide （SIC） surfaces was discussed in this work. To investigate the transformation, a quenching experiment was conducted and an X-ray diffractometer was used to measure the residual stress. The experimental results demonstrate that the significantly enhanced hydrophilicity was induced by the increasing thermal residual stress of SiC materials after the aqueous quenching. It was found that the decrease in the contact angle increased with the increasing quenching temperature. Quenching at 350℃ led to the change of contact angle from 89.28° to 70.88° for the smooth surface, while from 72.25° to 33.75° for the laser-textured surface with depth 8 μm. Further, the surface hydrophobicity was enhanced by the release of thermal residual stress after quenching, thereby leading to an increase in the contact angle over time. The transformation of wetting behaviors on laser textured SiC surfaces can be achieved mutually by the aqueous quenching method.
