Numerical Simulation of Temperature Distribution and Microstructural Correlation in TIG Welded Zircaloy-2 Fuel Pin Joints

In the nuclear industry, achieving high-quality welds requires careful study of the formation of the fusion zone and heat-affected zone, as these regions play a critical role in determining the joint’s metallurgical and mechanical properties. Accurate characterization of the fusion zone and heat affected zone depends on understanding the transient temperature distribution during welding. In this work, a multi-physics finite element model incorporating a moving heat source was developed to efficiently simulate the Tungsten inert gas welding process. The influence of welding current, arc distance, and rotational speed on thermal profiles was systematically investigated. Numerical predictions were validated through microstructural analysis, which confirmed close agreement between simulated temperature fields and experimentally observed microstructure. The fusion zone exhibited Widmanstätten structures that gradually transitioned into equiaxed grains in the parent metal. Hardness profiles were consistent with these microstructural variations, showing maximum hardness in the Widmanstätten region and a gradual decrease toward the base material. EBSD analysis indicated random grain orientations in the fusion zone due to the β → α phase transformation, whereas the parent material retained a strong basal texture resulting from the pilgering process.