Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of ...Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of granular bainite and -20 vol. % martensite. The fraction of retained austenite remains unchanged until tempering at 200 ℃, above which it decreases significantly. The increase of tempering temperature leads to decreases of both ultimate tensile strength and total elongation but decreases of both yield strength and reduction of area. The maximum and mini- mum values of impact toughness were observed after tempering at around 200 and 400 ℃, respectively. These effects are mainly attributed to the decomposition of martensite/austenite con stituents and the tempering effects in martensite. The tempering of the forged bainitic steel at around 200 ℃ results in an excellent combination of strength and toughness, which is comparable to that of the conventional quenched and-tempered 40Cr steel. Therefore, low-tempering treatment coupled with post-forging residual stress relieving is a feasible method to further improve the mechanical prooerties of the bainitic foging steel.展开更多
The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round...The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 C could significantly alleviate the susceptibility to HE by a relative decrease of * 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.展开更多
Fused deposition modelling and sintering(FDMS)is a potential metal additive manufacturing technology due to its low cost and high efficiency.The mixture of metal powder and binder goes through heating,extrusion,debind...Fused deposition modelling and sintering(FDMS)is a potential metal additive manufacturing technology due to its low cost and high efficiency.The mixture of metal powder and binder goes through heating,extrusion,debinding and sintering processes to produce the compact finished part.However,it is generally believed that parts produced by FDMS possess poor and anisotropic tensile properties,which always attributes to the weak interlayer combination.The current work aimed to enhance tensile properties and better understand the anisotropic fracture behavior of the 316L stainless steel prepared by FDMS.By process optimization,the yield strength and ultimate tensile strength obtained in this work are increased by 26.1%and 15.2%,based on the highest performance reported in previous studies.According to the ultimate tensile strength,the performance difference between the horizontal and vertical directions has been reduced to 27%.Furthermore,the experimental results indicated that the clustered irregular shape holes evolved from primitive voids prefer to distribute in the build direction,resulting in anisotropic tensile performance.It is suggested that the mechanical properties could be improved by applying a smaller extrusion diameter and rolling-assisted printing.In addition,the current FDMS parts show qualified performance for producing the customized and small batch components.展开更多
基金financially supported by the National Key Research&Development Program of China under grant No.2016YFB0300100the Fundamental Research Funds for the Central Universities(No.2014JBM108)the Prospective Joint Study of Industry-University Cooperation of Jiangsu Province under grant No.BY2015009-02
文摘Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of granular bainite and -20 vol. % martensite. The fraction of retained austenite remains unchanged until tempering at 200 ℃, above which it decreases significantly. The increase of tempering temperature leads to decreases of both ultimate tensile strength and total elongation but decreases of both yield strength and reduction of area. The maximum and mini- mum values of impact toughness were observed after tempering at around 200 and 400 ℃, respectively. These effects are mainly attributed to the decomposition of martensite/austenite con stituents and the tempering effects in martensite. The tempering of the forged bainitic steel at around 200 ℃ results in an excellent combination of strength and toughness, which is comparable to that of the conventional quenched and-tempered 40Cr steel. Therefore, low-tempering treatment coupled with post-forging residual stress relieving is a feasible method to further improve the mechanical prooerties of the bainitic foging steel.
文摘The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 C could significantly alleviate the susceptibility to HE by a relative decrease of * 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.
基金supported by the National Natural Science Foundation of China(Grant No.51805238)the Shenzhen Science and Technology Innovation Commission(Grant Nos.JCYJ202103241046100029,KQTD20170328154443162 and ZDSYS201703031748354)。
文摘Fused deposition modelling and sintering(FDMS)is a potential metal additive manufacturing technology due to its low cost and high efficiency.The mixture of metal powder and binder goes through heating,extrusion,debinding and sintering processes to produce the compact finished part.However,it is generally believed that parts produced by FDMS possess poor and anisotropic tensile properties,which always attributes to the weak interlayer combination.The current work aimed to enhance tensile properties and better understand the anisotropic fracture behavior of the 316L stainless steel prepared by FDMS.By process optimization,the yield strength and ultimate tensile strength obtained in this work are increased by 26.1%and 15.2%,based on the highest performance reported in previous studies.According to the ultimate tensile strength,the performance difference between the horizontal and vertical directions has been reduced to 27%.Furthermore,the experimental results indicated that the clustered irregular shape holes evolved from primitive voids prefer to distribute in the build direction,resulting in anisotropic tensile performance.It is suggested that the mechanical properties could be improved by applying a smaller extrusion diameter and rolling-assisted printing.In addition,the current FDMS parts show qualified performance for producing the customized and small batch components.
