The heat-affected zone (HAZ) of the low-alloy steel in dissimilar metal welds has been investigated by electron backscatter diffraction, scanning electron microscopy and atom probe tomography. The welding process generates a temperature gradient, creating two zones in the HAZ: a carbon depleted zone and a carbon non-depleted zone (NDZ). The evolution of the microstructure in the NDZ and the atomic distribution at the ferrite/ferrite and ferrite/cementite interfaces was investigated for different long-term thermal ageing conditions. Many alloying elements segregate to grain boundaries (ferrite/ferrite interfaces) with a different amount in relation to the misorientation of the grain boundaries, but only phosphorus (P) segregates to the ferrite/cementite interface. In addition, the amount of P segregation increases with the increase in temperature and ageing time and depends also on the structural parameters of the interface. The partitioning between cementite and ferrite phases presents a slight evolution with long-term thermal ageing, related to kinetic limitation.

中文翻译：

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热老化对铁素体/铁素体和铁素体/渗碳体界面原子再分布的影响

通过电子背散射衍射、扫描电子显微镜和原子探针断层扫描研究了异种金属焊缝中低合金钢的热影响区（HAZ）。焊接过程会产生温度梯度，在 HAZ 中产生两个区域：贫碳区和非贫碳区 (NDZ)。针对不同的长期热老化条件，研究了 NDZ 中微观结构的演变以及铁素体/铁素体和铁素体/渗碳体界面处的原子分布。许多合金元素偏析到晶界（铁素体/铁素体界面），其量与晶界的错误取向有关，但只有磷 (P) 偏析到铁素体/渗碳体界面。此外，P偏析量随着温度和时效时间的增加而增加，并且还取决于界面的结构参数。渗碳体和铁素体相之间的分配随着长期热时效呈现轻微演变，与动力学限制有关。