In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by m...In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by microstructural characterization and mechanical tests.The results showed that the microstructure of the coarse-grained heat-aff ected zone(CGHAZ)and the fine-grained heat-aff ected zone(FGHAZ)was mainly comprised of lath martensite,and a mixed microstructure consisting of intercritical ferrite,tempered martensite and retained austenite occurred in the intercritically heat-aff ected zone(ICHAZ)and the subcritically heat-aff ected zone(SCHAZ).Also,8–11%retained austenite and more or less Cu precipitates were observed in the simulated HAZs except for CGHAZ.Charpy impact test indicated that the optimum toughness was obtained in FGHAZ,which was not only associated with grain refinement,but also correlated with deformation-induced transformation of the retained austenite,variant confi guration as interleaved type and a relatively weak variant selection.The toughness of ICHAZ and SCHAZ exhibited a slight downtrend due to the presence of Cu precipitates.The CGHAZ has the lowest toughness in the simulated HAZs,which was attributed to grain coarsening and heavy variant selection.In addition,the contribution of Cu precipitates to yield strength in simulated HAZs was estimated based on Russell–Brown model.It demonstrated an inverse variation trend to toughness.展开更多
基金financially supported by the National Key Research and Development Program of China(13th Five-Year Plan)with the Contract No.2016YFB0300601the National High Technology Research and Development Program of China(No.2012AA03A508)。
文摘In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by microstructural characterization and mechanical tests.The results showed that the microstructure of the coarse-grained heat-aff ected zone(CGHAZ)and the fine-grained heat-aff ected zone(FGHAZ)was mainly comprised of lath martensite,and a mixed microstructure consisting of intercritical ferrite,tempered martensite and retained austenite occurred in the intercritically heat-aff ected zone(ICHAZ)and the subcritically heat-aff ected zone(SCHAZ).Also,8–11%retained austenite and more or less Cu precipitates were observed in the simulated HAZs except for CGHAZ.Charpy impact test indicated that the optimum toughness was obtained in FGHAZ,which was not only associated with grain refinement,but also correlated with deformation-induced transformation of the retained austenite,variant confi guration as interleaved type and a relatively weak variant selection.The toughness of ICHAZ and SCHAZ exhibited a slight downtrend due to the presence of Cu precipitates.The CGHAZ has the lowest toughness in the simulated HAZs,which was attributed to grain coarsening and heavy variant selection.In addition,the contribution of Cu precipitates to yield strength in simulated HAZs was estimated based on Russell–Brown model.It demonstrated an inverse variation trend to toughness.
