C-1.5Mn-2.5Ni-0.5Cr-0.5Mo合金焊缝组织的演化机制

Microstructure of weld metal C-1.5Mn-2.5Ni-0.5Cr-0.5Mo alloy

利用光学显微镜、扫描电镜和透射电镜研究了C-1.5Mn-2.5Ni-0.5Cr-0.5Mo合金系焊缝金属的微观组织,并通过Thermal-calc软件计算焊缝金属Fe-Ni相图,进而研究了焊缝金属从液相凝固到室温组织整个相变过程。此外还测试了焊缝金属的基本力学性能。研究表明:液态金属初生相为δ-铁素体,并以柱状方式生长,形成δ-铁素体柱状晶。温度下降,δ-铁素体开始向奥氏体转变,奥氏体晶粒也以柱状方式生长,形成柱状奥氏体晶粒。温度继续下降,在奥氏体晶界处最先发生相变形成贝氏体,而奥氏体内部最后发生相变转变成马氏体。原奥氏体晶界形核以及贝氏体侧向形核导致贝氏体呈交织状分布。焊缝金属具有良好的低温韧性,这是因为组织中含有大量交织状贝氏体。

Microstructure of weld metal C-1.5Mn-2.5Ni-0.5Cr-0.5Mo alloy was investigated by means of optical microscopy,scanning electron microscopy and transmission electron microscopy.The Fe-Ni phase diagram was calculated with thermal-calc software.Solidification and transformation of the weld metal during cooling process was analyzed.Mechanical properties of the weld metal were tested.The results indicate that delta ferrite is the primary phase during solidification and grows in a columnar manner to transform austenite.With further cooling,bainite forms firstly at the columnar austenite grain boundaries,and then,the austenite transforms into martensite.The interlace bainite is formed as a result of bainite nucleation at austenite grain boundaries and the side of prior-formed bainite lath.The good toughness of weld metal is attributed to large amount of the interlace bainite.