Dissimilar materials joining by hybrid FSW involve preheating the harder material ahead of the FSW tool, which reduces the vertical force and improves the weld quality by enhancing the material flow. In this work, both experimental and numerical analyses were conducted for the friction stir welding (FSW) and plasma-assisted friction stir welding (PAFSW) of dissimilar steels such as DH36 shipbuilding steel and AISI 1008 steel. The comparative study was performed on the thermal history, vertical force, mechanical and microstructural characterizations under different welding conditions. The 3D transient thermal phenomenological models were established using Abaqus/CAE 2017 finite element (FE) software package. The moving heat source models for FSW and PAFSW were successfully established, which were embedded in a Fortran code and fed to Abaqus/CAE through DFLUX subroutine. The additional heat source, i.e. plasma arc heat source, was modelled using the Gaussian distribution of heat flux. The stir zone isotherms of the developed numerical models and the transient thermal profiles in the FSW and PAFSW were matched fairly well with experimental results. For the reliable comparative study, the consequence of FSW parameters (i.e. traverse speed and rotational speed) and preheating parameters (i.e. plasma offset and preheating current) on thermal history was investigated. It was observed that the assistance of the plasma preheating ahead of FSW tool was significantly reduced the grain size and vertical force. In contrast, the hardness and the impact toughness values were increased compared to that of FSW.

通过混合FSW连接的异种材料涉及在FSW工具之前对较硬的材料进行预热，这会减小垂直力并通过增强材料流动性来改善焊接质量。在这项工作中，对DH36船用钢和AISI 1008钢等异种钢的搅拌摩擦焊（FSW）和等离子辅助搅拌摩擦焊（PAFSW）进行了实验和数值分析。对不同焊接条件下的热历史，垂直力，机械和微观结构特征进行了比较研究。使用Abaqus / CAE 2017有限元（FE）软件包建立了3D瞬态热现象学模型。成功建立了FSW和PAFSW的移动热源模型，它们被嵌入到Fortran代码中，并通过DFLUX子例程提供给Abaqus / CAE。使用热通量的高斯分布对附加热源（即等离子弧热源）进行建模。所开发数值模型的搅拌区等温线以及FSW和PAFSW中的瞬态热剖面与实验结果相当吻合。为了进行可靠的比较研究，研究了FSW参数（即移动速度和旋转速度）和预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。使用热通量的高斯分布对附加热源（即等离子弧热源）进行建模。所开发数值模型的搅拌区等温线以及FSW和PAFSW中的瞬态热剖面与实验结果相当吻合。为了进行可靠的比较研究，研究了FSW参数（即移动速度和旋转速度）和预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。使用热通量的高斯分布对附加热源（即等离子弧热源）进行建模。所开发数值模型的搅拌区等温线以及FSW和PAFSW中的瞬态热剖面与实验结果相当吻合。为了进行可靠的比较研究，研究了FSW参数（即移动速度和旋转速度）和预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。所开发数值模型的搅拌区等温线以及FSW和PAFSW中的瞬态热剖面与实验结果相当吻合。为了进行可靠的比较研究，研究了FSW参数（即移动速度和旋转速度）和预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。所开发数值模型的搅拌区等温线以及FSW和PAFSW中的瞬态热剖面与实验结果相当吻合。为了进行可靠的比较研究，研究了FSW参数（即移动速度和旋转速度）和预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。考察了横移速度和旋转速度）以及预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。考察了横移速度和旋转速度）以及预热参数（即等离子偏移和预热电流）对热历史的影响。观察到，在FSW工具之前进行等离子预热有助于显着减小晶粒尺寸和垂直力。相反，与FSW相比，硬度和冲击韧性值有所增加。