COMPUTATIONAL MODELING OF GMAW PROCESS FOR JOINING DISSIMILAR ALUMINUM ALLOYS Vaibhav K. Arghode and Arvind Kumar Department of Mechanical Engineering, Indian Institute of Science, Bangalore, India Suresh Sundarraj General Motors R&D, India Science Lab, Bangalore, India Pradip Dutta Department of Mechanical Engineering, Indian Institute of Science, Bangalore, India A three-dimensional transient model is developed to solve for heat transfer, fluid flow, and species distribution during a continuous gas metal arc welding (GMAW) process for joining dissimilar aluminum alloys. The phase-change process during melting and solidification is modeled using a fixed-grid enthalpy-porositytechnique, and Scheil’s model is used to deter- mine coupling among composition, temperature, and the liquid fraction. The effect of molten droplet addition to the weld pool is simulated using a ‘‘cavity’’ model, in which the droplet heat and species addition to the molten pool are considered as volumetric heat and species sources, respectively, distributed in an imaginary cylindrical cavity within the molten pool. To establish the model for joining dissimilar alloys, results for joining two pieces of a similar alloy are also presented. The dissimilar welding model is demonstrated using a case study in which a plate of wrought aluminum alloy (with approximately 0.5 wt% Si) is butt-welded to an aluminum cast alloy plate (with approximately 10 wt% Si) Si) of equal thickness using a GMAW process. Macrosegregation, along with the associa- ted heat transfer and fluid flow phenomena and their role in the weld pool development, are discussed. The model is able to capture some of the key features of the process, such as differential heating of the two alloys, asymmetric weld pool development, mixing of the molten alloys, and the final composition after solidification. 1. INTRODUCTION Fusion welding is an important manufacturing technique that has attained a state of maturity in the past few decades. The physical processes that take place dur- ing fusion welding are fairly well documented [1]. Microstructure of the weldment, which determines the mechanical properties of the product, is understood in terms Received 6 June 2007; accepted 24 July 2007. Vaibhav K. Arghode, Arvind Kumar, and Pradip Dutta gratefully acknowledge the financial support of General Motors Corporation, USA. Address correspondence to Pradip Dutta, Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India. E-mail: pradip@mecheng.iisc.ernet.in 432 Numerical Heat Transfer, Part A, 53: 432–455, 2008 Copyright # Taylor & Francis Group, LLC ISSN: 1040-7782 print=1521-0634 online DOI: 10.1080/10407780701632585