不同钢中马氏体与贝氏体组织形貌

Morphologies of martensite and bainite in different steels

不同热处理工艺下,钢中马氏体与贝氏体含量与形貌不同,造成钢的力学性能具有差异。通过对45钢、40Cr钢、38CrSi钢进行不同的热处理,获得不同形貌的马氏体、贝氏体组织。采用OM、SEM、TEM对不同钢中的马氏体、贝氏体进行组织形貌观察及分析,并估算了其含量。结果表明,不同碳含量的钢经过水冷淬火热处理后,马氏体组织形貌随碳含量的升高而变化,由低碳板条状过渡到中碳针状板条状并存。同一种钢经过不同热处理后可得到不同形貌的贝氏体组织,45钢、40Cr钢、38CrSi钢贝氏体组织多在晶界处形核并向晶内长大。无碳贝氏体与粒状贝氏体的析出与热处理工艺有关,贝氏体形貌随碳含量与热处理温度的降低由羽毛状逐步过渡到无碳贝氏体。

The mechanical properties of the steel are different under different heat treatment processes,due to the different contents and morphologies of martensite and bainite in the steel.Different heat treatment processes of 45 steel,40Cr steel and 38CrSi steel were used to obtain the martensite and bainite structure.The micromorphologies of martensite and bainite in different steels were observed and analyzed by optical microscopy,scanning electron microscopy and transmission electron microscopy,and their contents were estimated.The results show that the morphology of martensite in steels with different carbon contents after water quenching changes with the increase in carbon content,and the transition is from low-carbon lath to medium-carbon needle-strip coexistence.After different heat treatments of the same kind of steel,bainite with different morphologies can be obtained.Most bainite of 45steel,40Cr steel and 38CrSi steel nucleates at grain boundaries and grows inside the grain.The precipitation of carbonless bainite and granular bainite is related to the heat treatment process.The bainite morphology gradually changes from feather bainite to carbon-free bainite as the carbon content and heat treatment temperature decrease.