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本文研究马氏体钢12Ni4CrMo中奥氏体形成过程。马氏体预淬火温度为860℃。应用透射及扫描电子显微镜观察、分析新生奥氏体及基体组织的形态与精细结构。结果表明:将钢加热至(a+γ)双相区低温阶段,沿马氏体板条界形成针状奥氏体;沿原始γ晶界形成粒状奥氏体。可借助再淬火后钢中的残余奥氏体来确定新生奥氏体形成的晶体学取向关系。在双相区加热的高温阶段,针状奥氏体转化为粒状奥氏体。这主要是由于原始γ晶界上的粒状奥氏体向晶内扩张并吞食针状奥氏体,而非由于针状奥氏体本身的合并。
In this paper, martensitic steel 12Ni4CrMo austenite in the formation process. Pre-quenching martensite temperature of 860 ℃. Transmission electron microscopy and scanning electron microscopy were used to analyze the morphology and fine structure of nascent austenite and matrix. The results show that the austenite is formed along the martensite slab boundary when the steel is heated to the low temperature of (a + γ) dual phase zone and granular austenite is formed along the original γ grain boundary. With the help of residual austenite in the steel after re-quenching, the crystallographic orientation relationship of nascent austenite can be determined. In the high-temperature phase of the heating in the biphasic zone, acicular austenite is transformed into granular austenite. This is mainly due to the granular austenite on the original γ grain boundaries expanding intragranularly and swallowing acicular austenite instead of the consolidation of acicular austenite itself.