To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray dif...To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray diffraction and nanoindentation test have been used to detect the residual stress and micro-property.The samples with deformation rate of 0-5.59%or annealing at 550℃ are analyzed.The results show that,due to the coupling effect of thermal expansion and cold contraction and the volume expansion of microstructural transformation from austenite to ferrite,compressive residual stress was found inside the hot-rolled samples.With the increase in cold compression deformation,the dislocation density increased and the microhardness increased gradually,and there is no obvious rule for the change of mean nano-hardness in micro-zone for the center of samples.However,the uniformity of nano-hardness in the micro-zone increased first and then decreased,and the value of residual stress has obvious corresponding relationship with the uniformity of micro-zone property.The cold compression deformation with appropriate reduction rate can reduce residual stress and improve nano-hardness uniformity of the hot-rolled samples,but more deformation(such as reduction rateε=5.59%)makes residual stress increase and makes uniformity of nano-hardness deteriorate.展开更多
Bainite transformation kinetics,microstructure,and mechanical properties were comparably investigated by X-ray diffraction,scanning electron microscopy,electron backscatter diffraction,transmission electron microscopy...Bainite transformation kinetics,microstructure,and mechanical properties were comparably investigated by X-ray diffraction,scanning electron microscopy,electron backscatter diffraction,transmission electron microscopy observation,and tensile and impact tests for two treatments:with and without quenching before isothermal bainite transformation at 300°C.Both the incubation time and growth stage of bainite transformation are accelerated by the introduction of prior martensite,especially the former.In addition,the bainite microstructure around the prior martensite is refined and shows a similar orientation with the martensite due to the strain field caused by the existence of prior martensite.The finer bainite microstructure and prior martensite improve the strength and hardness of the high-carbon nano-bainitic steel.Although the presence of prior martensite and low misorientation relationship between the martensite and the adjacent bainite microstructure are prejudicial to impact toughness,the nanoscale bainite microstructure can inhibit the crack propagation and then improve the impact toughness of the high-carbon nano-bainitic steel.展开更多
基金support from Guangxi Science and Technology Major Project of China(Grant No.AA18242012-1).
文摘To reduce internal residual stress and homogenize micro-property of hot-rolled ferrite steel,the cold compression deformation method with small reduction rate has been performed in the hot-rolled samples,and X-ray diffraction and nanoindentation test have been used to detect the residual stress and micro-property.The samples with deformation rate of 0-5.59%or annealing at 550℃ are analyzed.The results show that,due to the coupling effect of thermal expansion and cold contraction and the volume expansion of microstructural transformation from austenite to ferrite,compressive residual stress was found inside the hot-rolled samples.With the increase in cold compression deformation,the dislocation density increased and the microhardness increased gradually,and there is no obvious rule for the change of mean nano-hardness in micro-zone for the center of samples.However,the uniformity of nano-hardness in the micro-zone increased first and then decreased,and the value of residual stress has obvious corresponding relationship with the uniformity of micro-zone property.The cold compression deformation with appropriate reduction rate can reduce residual stress and improve nano-hardness uniformity of the hot-rolled samples,but more deformation(such as reduction rateε=5.59%)makes residual stress increase and makes uniformity of nano-hardness deteriorate.
基金the National Natural Science Foundation of China(Grant No.51774033)Innovative Talents Fund Gold Project from University of Science and Technology Beijing.
文摘Bainite transformation kinetics,microstructure,and mechanical properties were comparably investigated by X-ray diffraction,scanning electron microscopy,electron backscatter diffraction,transmission electron microscopy observation,and tensile and impact tests for two treatments:with and without quenching before isothermal bainite transformation at 300°C.Both the incubation time and growth stage of bainite transformation are accelerated by the introduction of prior martensite,especially the former.In addition,the bainite microstructure around the prior martensite is refined and shows a similar orientation with the martensite due to the strain field caused by the existence of prior martensite.The finer bainite microstructure and prior martensite improve the strength and hardness of the high-carbon nano-bainitic steel.Although the presence of prior martensite and low misorientation relationship between the martensite and the adjacent bainite microstructure are prejudicial to impact toughness,the nanoscale bainite microstructure can inhibit the crack propagation and then improve the impact toughness of the high-carbon nano-bainitic steel.
