Process Modeling of Ti-6Al-4V Linear Friction Welding (LFW)

A fully coupled thermomechanical finite-element analysis of the linear friction welding (LFW) process is combined with the basic physical metallurgy of Ti-6Al-4V to predict microstructure and mechanical properties within the LFW joints (as a function of the LFW process parameters). A close examination of the experimental results reported in the open literature revealed that the weld region consists of a thermomechanically affected zone (TMAZ) and a heat-affected zone (HAZ) and that the material mechanical properties are somewhat more inferior in the HAZ. Taking this observation into account, a model for microstructure-evolution during LFW was developed and parameterized for the Ti-6Al-4V material residing in the HAZ. Specifically, this model addresses the problem of temporal evolution of the prior β-phase grain size (the dominant microstructural parameter in the HAZ) during the LFW process. This model is next combined with the well-established property versus microstructure correlations in Ti-6Al-4V to predict the overall structural performance of the LFW joint. The results obtained are found to be in reasonably good agreement with their experimental counterparts suggesting that the present computational approach may be used to guide the selection of the LFW process parameters to optimize the structural performance of the LFW joints.