【摘要】 使用光学显微镜、SEM、TEM、XRD观察G50钢淬火和低温回火后的微观组织形貌,结合低温回火前后G50钢的屈服强度和冲击韧性等力学性能的变化,分析其强韧化机理。结果表明,淬火态G50钢微观组织主要为细小的板条状马氏体,使用TEM可以观测到有残留奥氏体薄膜在马氏体板条之间,残留奥氏体量很低。G50钢的超高强度来自马氏体相变和晶粒的细化,低温回火处理后G50钢的微观组织是细小的板条状回火马氏体,在保持强度的同时提高了冲击韧性。更多还原

【Abstract】 Optical microscope,scanning electron microscope and transmission electron microscope were used to observe microstructure of G50 steel after quenching and low temperature tempering. Based on changes of yield strength,impact toughness and other mechanical properties of the G50 steel before and after low temperature tempering,the strengthening and toughening mechanisms were analyzed. SEM micrographs show that microstructure of quenched G50 steel is mainly tiny martensite lath. TEM micrographs show that there are a few retained austenite films existing between martensite lath boundaries. It is martensitic transformation and grain refinement that give the ultra high strength to G50 steel. Microstructure of G50 steel after low temperature tempering is tiny tempered martensite lath,which improves impact toughness and maintains ultra high strength.更多还原