9Ni钢组织演变、合金元素配分及增韧机理的研究

Research on microstructure evolution,alloy elements partitioning and toughening mechanism of 9Ni steel

为了研究9Ni钢热处理过程中的组织演变和合金元素配分对强韧化的影响,采用QT(Quenching+Tempering)和QLT(Quenching+Lamellarizing+Tempering)工艺对9Ni钢进行了热处理,并详细分析了热处理过程中组织和成分配分的变化规律.结果表明:奥氏体化淬火后存在极少量的残余奥氏体(γR),主要富C和Si.580℃回火1 h时,QT工艺条件下原奥氏体晶界上逆转奥氏体(γ')能富C、Si、Mn和Ni元素,晶内的γ'中无明显Ni和Mn富集;QLT处理后,合金元素发生了配分,所有富合金元素相中均富集C、Si、Mn和Ni元素.两相区保温后实现增韧归因于:板条马氏体基体的大角度晶界比例增加、晶粒细化;组织结构得到优化;增加了γ'形核点,使得γ'量增加,导致马氏体基体净化程度进一步提高.

To reveal the influence of microstructure evolution and alloy elements partitioning on strength and toughness for 9Ni steel,QT and QLT heat treatment were employed and the microstructure evolution and alloy elements partitioning rules of the two processes were systematically analyzed.The results show that there is few of γR with a C and Si enrichment after austenitizing and quenching.When QT process with tempering parameters 580 ℃ × 1 h is adopted,there are C,Si,Mn and Ni enrichment in the big size γ′ located at prior austenite boundary,while there is no Ni and Mn enrichment in γ′ located in prior austenite grain.However,when QLT process with the same tempering parameters of QT is adopted,all of alloy elements C,Si,Mn,Ni can be partitioning from matrix to the microstructure which collects austenite stability elements.The double-phase region heat treatment toughening factors of 9Ni steel are likely to be the ratio of high angle grain boundary of martensite matrix,the optimization of constitutes of microstructure and the increase of nucleation sites of γ′ which is helpful to the purification of martensite matrix.