Special Issue Paper
(Received 31 December 2014; accepted 9 July 2015)
Published Online: 30 November 2015
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Metastable β-titanium alloys are finding increasingly wider applications in structural components in aerospace, energy, and chemical industries because of their formability and heat-treatment possibilites. Components from these alloys are usually welded by processes, such as gas tungsten arc welding (GTAW), electron beam welding (EBW), and laser beam welding (LBW). Post-weld heat treatment improves the strength of the weld because of the precipitation of α phase and TiCr2 particles. In β-titanium alloys, the location, distribution and morphology of α precipitates in β matrix plays an important role in the performance of the welded components. In this work, we simulate different welding processes using SYSWELD® software and obtain realistic thermal cycles after calibrating the fusion zone dimensions with known experimental data. These cycles are then used to program the heat-affected zone (HAZ) cycles in Gleeble® 3800 to study their effect on the microstructure of the β-titanium alloy. Both continuous and pulsed welding conditions are used for the welding process. Microstructure characterization was performed using scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM). Precipitates of α phase below 0.2μm are seen to be uniform across the β grain but the number density is not uniform across different grains of β. We discuss the characterization results in light of existing models in the literature. The α precipitation and hardness variation are correlated with welding cycles. A combination of computational and physical simulation tools is proposed to reduce the cycle to find optimal choice in the fabrication process design space.
Rahul, M. R.
Research Scholar, Dept. of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai
Associate Professor, Dept. of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai
Stock #: MPC20140065