Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous mi...Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.展开更多
The cold rolling deformation textural evolution of an interstitial-free （IF） steel sheet is investigated by experiment and simulation. The microstructure of the IF steel is observed by transmission electron microsco...The cold rolling deformation textural evolution of an interstitial-free （IF） steel sheet is investigated by experiment and simulation. The microstructure of the IF steel is observed by transmission electron microscopy （TEM）. The relationship between the deformation behavior of individual grain and the grain orientation are connected by Taylor factor M. The results show that the grains with higher Taylor factor are deformed slighter than those with lower ones. By considering the heterogeneous deformation, the texture simulation result can be greatly improved.展开更多
测定了稀土脱氧和铝稀土复合脱氧钢焊接热影响区(HAZ)的连续冷却转变曲线,分析了2种钢中的夹杂物种类及其HAZ的显微组织和常温冲击韧性。得到如下结论:稀土脱氧使钢中主要夹杂物从Mn S转变为RE2O2S+Mn S,而铝稀土复合脱氧钢中夹杂物主要...测定了稀土脱氧和铝稀土复合脱氧钢焊接热影响区(HAZ)的连续冷却转变曲线,分析了2种钢中的夹杂物种类及其HAZ的显微组织和常温冲击韧性。得到如下结论:稀土脱氧使钢中主要夹杂物从Mn S转变为RE2O2S+Mn S,而铝稀土复合脱氧钢中夹杂物主要是Ce Al O3+Ce2S3+Mn S。稀土脱氧钢HAZ中能获得晶内铁素体的冷速较宽,约为0.5~7.5℃/s。铝稀土复合脱氧钢HAZ获得晶内铁素体组织较稀土脱氧钢要困难一些,适合晶内铁素体形成的冷速变窄为1~3℃/s,HAZ中晶内铁素体的含量明显低于稀土处理钢,Al脱氧弱化了稀土处理对钢HAZ组织的改善作用。焊接热输入线能量为100 k J/cm时,稀土脱氧能够明显改善钢HAZ的室温冲击韧性。展开更多
Heterogeneous microstructure-induced mechanical responses in EH420 shipbuilding steel welded joint by electro-gas welding processed have been systematically studied by scanning electron microscopy,electron backscatter...Heterogeneous microstructure-induced mechanical responses in EH420 shipbuilding steel welded joint by electro-gas welding processed have been systematically studied by scanning electron microscopy,electron backscatter diffraction and mechanical testing.Comparing with the coarse-grained heat-affected zone(CGHAZ),the weld metal presents higher toughness(129.3 J vs.37.3 J)as it contains a large number of acicular ferrites with high-angle grain boundaries(frequency 79.2%)and special grain boundary∑3(frequency 55.3%).Moreover,coarse austenite grains in CGHAZ and slender martensite–austenite constituents between bainite laths may likely facilitate crack propagation.Polygonal ferrites and tempered pearlites formed at the junction of the fine-grained heat-affected zone and the intercritical heat-affected zone induced a softened zone with an average hardness of 185 HV0.5,which is the main reason for the occurrence of tensile fracture.展开更多
基金This work was financially supported by the National Key Research and Development Program of China(No.2017YFB 0304800)One of the authors,H.Guo,would like to express her gratitude for the financial support of China Scholarship Council(award for one year visiting at Northwestern University in the USA,No.201706465056).
文摘Here we present a novel approach of intercritical heat treatment for microstructure tailoring,in which intercritical annealing is introduced between conventional quenching and tempering.This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite,resulting in a low yield ratio(YR)and high impact toughness in a high-strength low-alloy steel.The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing,in comparison to the steel with full martensitic microstructure.The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering.The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases,but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.
基金the National Natural Science Foundation of China （Grant No. 50671021） Program for New Century Excellent Talents in University （Grant No. NCET-06-0287）.
文摘The cold rolling deformation textural evolution of an interstitial-free （IF） steel sheet is investigated by experiment and simulation. The microstructure of the IF steel is observed by transmission electron microscopy （TEM）. The relationship between the deformation behavior of individual grain and the grain orientation are connected by Taylor factor M. The results show that the grains with higher Taylor factor are deformed slighter than those with lower ones. By considering the heterogeneous deformation, the texture simulation result can be greatly improved.
文摘测定了稀土脱氧和铝稀土复合脱氧钢焊接热影响区(HAZ)的连续冷却转变曲线,分析了2种钢中的夹杂物种类及其HAZ的显微组织和常温冲击韧性。得到如下结论:稀土脱氧使钢中主要夹杂物从Mn S转变为RE2O2S+Mn S,而铝稀土复合脱氧钢中夹杂物主要是Ce Al O3+Ce2S3+Mn S。稀土脱氧钢HAZ中能获得晶内铁素体的冷速较宽,约为0.5~7.5℃/s。铝稀土复合脱氧钢HAZ获得晶内铁素体组织较稀土脱氧钢要困难一些,适合晶内铁素体形成的冷速变窄为1~3℃/s,HAZ中晶内铁素体的含量明显低于稀土处理钢,Al脱氧弱化了稀土处理对钢HAZ组织的改善作用。焊接热输入线能量为100 k J/cm时,稀土脱氧能够明显改善钢HAZ的室温冲击韧性。
基金the National Natural Science Foundation of China(Grant Nos.U20A20277,51861130361,51861145312,51850410522,5201101443,and 52011530180)the Newton Advanced Fellowship by Royal Society(Grant No.RP12G0414)+5 种基金the Royal Academy of Engineering(No.TSPC1070)the Special Fund for Key Program of Science and Technology of Liaoning Province(Grant No.2019JH1/101000014)the Research Fund for Central Universities(Grant Nos.N172502004 and N2025025)the Xingliao Talents Program(Nos.XLYC1807024 and XLYC1802024)the Regional Innovation Joint Fund of Liaoning Province(No.2020-YKLH-39)funded in part by the National Research Foundation of South Africa(No.BRICS171211293679)。
文摘Heterogeneous microstructure-induced mechanical responses in EH420 shipbuilding steel welded joint by electro-gas welding processed have been systematically studied by scanning electron microscopy,electron backscatter diffraction and mechanical testing.Comparing with the coarse-grained heat-affected zone(CGHAZ),the weld metal presents higher toughness(129.3 J vs.37.3 J)as it contains a large number of acicular ferrites with high-angle grain boundaries(frequency 79.2%)and special grain boundary∑3(frequency 55.3%).Moreover,coarse austenite grains in CGHAZ and slender martensite–austenite constituents between bainite laths may likely facilitate crack propagation.Polygonal ferrites and tempered pearlites formed at the junction of the fine-grained heat-affected zone and the intercritical heat-affected zone induced a softened zone with an average hardness of 185 HV0.5,which is the main reason for the occurrence of tensile fracture.
