Residual Stress Distributions in Dissimilar Titanium Alloy Diffusion Bonds Produced From Powder Using Field-Assisted Sintering Technology (FAST-DB)

Abstract

The conventional approach when engineering components manufactured from titanium is to design the thermomechanical processing to develop an optimal microstructure in a single alloy. However, this conventional approach can lead to unnecessary over-engineering of components, particularly when only a specific subcomponent region is under demanding service stresses and environments. One approach being developed to join multiple alloys in a single component and enhance engineering performance and efficiency is FAST-DB—whereby multiple alloys in powder form are diffusion bonded (DB) using field-assisted sintering technology (FAST). But the joining of multiple alloys using conventional welding and joining techniques can generate high residual stress in the bond region that can affect the mechanical performance of the components. In this study, the residual stress distribution across dissimilar titanium alloy diffusion bonds, processed from powder using FAST, were measured using X-Ray diffraction and the Contour method. The measurements show low residual stress in the bulk material processed with FAST as well as in the diffusion bond region. In addition, FAST-DB preforms subsequently hot forged into different near-net shapes were also analyzed to understand how the residual stress in the bond region is affected by a subsequent processing. Overall, no sharp transitions in residual stress was observed between the dissimilar alloys. This study reinforces confidence in the solid-state FAST process for manufacturing next generation components from multiple titanium alloy powders.

Influence of Different Filler Metals on the Mechanical and Microstructural Characteristics of Arc-Welded Joints Made of Dissimilar Titanium Alloys

“…For the manufacture of the heat resistant components used for aerospace and motorsport applications, it is a common practice to require the joining together of different titanium alloys displaying different microstructures. In general, for welding dissimilar materials, the potential issues for attaining good joints are ascribable to differences in melting temperature and thermal expansion coefficients of the two materials, which may lead to higher thermal stresses and result in cracking in the transition zone between the materials [1]. Hence, challenges in joining an α + β titanium alloy to an α Ti one are mainly represented by the mismatch in mechanical properties, melting temperatures in the case when a molten phase is involved, crystal structures, and, perhaps more importantly, mutual solubility.…”