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高温金相显微镜观察发现，珠光体钢（ Ｚ Ｇ２０ Ｓｉ Ｍｎ） 与奥氏体焊材（ Ａ３０７ 、 Ａ４５７） 熔合区确实存在马氏体相变，且在约４００ ℃至室温均有相变产生。经透射电镜观察，熔合区马氏体为低碳板条马氏体，亚结构主要是位错，有少量孪晶亚结构。熔合区碳化物主要产生于焊后热处理过程中，其类型主要为 Ｍ２３ Ｃ６ ，也有部分 Ｍ７ Ｃ３ 。碳化物主要在马氏体上以及马氏体或铁素体和奥氏体界面析出。马氏体带、碳化物带宽度主要受 Ｎｉ 含量的控制，提高 Ｎｉ 含量使它们变窄，熔合区韧性提高。
High-temperature metallurgical microscopy revealed that martensitic transformation did exist in the fusion zone of ZG20SiMn and austenitic welding consumables (A307, A457), and phase transition occurred at about 400 ℃ to room temperature. The transmission electron microscopy shows that the martensite in the fusion zone is a martensite of low-carbon lath, the sub-structures are mainly dislocations and the twins are sub-structures. Fused zone carbide mainly produced in the post-weld heat treatment process, the type is mainly M23 C6, there are some M7 C3. Carbides mainly in the martensite and martensite or ferrite and austenite interface precipitation. Martensite zone, carbide width is mainly controlled by the Ni content, increasing the Ni content so that they narrow, the toughness of the fusion zone increased.