In the present investigation, a new endeavor has been made to analyze the impact of the secondary process (post-weld heat treatment (PWHT)) as well as Ni addition on the microstructure and mechanical characteristics of welds. Welds between similar joining materials from duplex stainless steels (DSS), as well as super DSS (SDSS), were made by the gas tungsten arc welding (GTAW) process. For DSS, after PWHT with the addition of Ni element, the amount of austenite rises and becomes more uniformly distributed with curved boundaries, while for SDSS, the microstructure mainly consists of intergranular and Widmanstätten austenite. According to the comparison of phase percentages obtained based on both ASTM E1245 and ASTM E562, a good balance between ferrite and austenite phases of joint materials was achieved. X-ray diffraction analyses on both joints revealed that phases are mainly ferrite and austenite with different lattice parameters without evidence of unwanted intermetallic phases. The addition of Ni increases the hardness values of DSS weld metal compared to the base metal due to an increased amount of Widmanstätten austenite and ferrite in the microstructure. The lowest ductility was obtained for the SDSS weld sample with the addition of Ni and PWHT because of the existence of secondary austenite in the weld metal and the Widmanstätten morphology of the austenite. The effect of PWHT on the development of microstructure and mechanical behaviors was more than the effect of nickel powder on weld samples.

中文翻译：

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Ni和PWHT对GTA焊接双相不锈钢和超级双相不锈钢接头显微组织演变和力学性能的影响：比较研究

在目前的研究中，我们做出了新的努力来分析二次加工（焊后热处理（PWHT））以及添加镍对焊缝微观结构和机械特性的影响。双相不锈钢 (DSS) 以及超级 DSS (SDSS) 的类似连接材料之间的焊接采用钨极气体保护焊 (GTAW) 工艺进行。对于DSS，添加Ni元素的PWHT后，奥氏体数量增加，并且分布更加均匀，边界弯曲，而对于SDSS，显微组织主要由晶间奥氏体和魏德曼组织组成。根据基于 ASTM E1245 和 ASTM E562 获得的相百分比的比较，接头材料的铁素体相和奥氏体相之间实现了良好的平衡。对两个接头的 X 射线衍射分析表明，相主要是具有不同晶格参数的铁素体和奥氏体，没有证据表明存在不需要的金属间相。与母材相比，添加 Ni 提高了 DSS 焊缝金属的硬度值，因为显微组织中魏德曼组织奥氏体和铁素体的含量增加。由于焊缝金属中存在二次奥氏体以及奥氏体的魏德曼组织形态，添加 Ni 和 PWHT 的 SDSS 焊缝样品获得了最低的延展性。PWHT 对显微组织和机械性能发展的影响大于镍粉对焊缝样品的影响。