FAST- forge of novel Ti-6Al-4V/Ti-6Al-2Sn-4Zr-2Mo bonded, near net shape forgings from surplus AM powder

Materials Science and Technology

Sagoo

et al. 2023

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Titanium alloys are a key part of an armour designer's toolset due to their high ballistic mass efficiency. However, titanium's high cost has restricted its use in military land-based vehicles. In this study, the effect of different processing routes on the microstructure, texture, ballistic performance V50 and deformation modes of Ti-6Al-4V armour plate is investigated. Plates were fabricated via conventional hot rolling and the powder metallurgy techniques of HIP and FAST. The plate failure modes varied significantly with the microstructure while the formation of adiabatic shear bands seems to be influenced by crystallographic texture. The rolled plate exhibited the best performance due to a strong transverse-type texture perpendicular to the projectile direction.

Section: Introductionmentioning

confidence: 99%

Effect of processing route on ballistic performance of Ti-6Al-4V armour plate

Fernandez-Silva

Materials Science and Technology

Sagoo

et al. 2023

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Deformation Behaviour of a FAST Diffusion Bond Processed from Dissimilar Titanium Alloy Powders

Lunt

Baxter

et al. 2021

Metall Mater Trans A

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Titanium alloys have a high strength-to-weight ratio, fatigue performance and excellent corrosion resistance, and therefore are widely used in the aerospace sector due to their ability to withstand severe mechanical and thermal stresses in service. There are numerous cases where it would be desirable to use different titanium alloys in defined subcomponent regions to improve performance and efficiency. Conventional processing routes do not permit components to be produced with multiple titanium alloys and thus, design efficiency and optimization of component properties is compromised or over-engineered. In this study, a hybrid solid-state consolidation route is presented whereby field assisted sintering technology (FAST) is exploited to diffusion bond (DB) dissimilar titanium alloy powders in defined regions—a process termed FAST-DB. Titanium alloy powders Ti-6Al-4V (Ti-64) and Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) were bonded using FAST in order to study the tensile deformation behavior and strain localization across a dissimilar alloy solid-state bond. FAST-DB was carried out at the sub- and super- beta transus temperatures of both alloys to generate dissimilar microstructure morphologies across the bond. In all cases, diffusion bonds showed excellent structural integrity with no defects and a smooth hardness profile across the bond. The deformation characteristics of the bonds was studied using two different tensile test approaches. The first approach used ASTM standard specimens to measure the mechanical properties of FAST-DB samples and study the location of the tensile failure. The second approach used a microtester and optical Digital Image Correlation to capture the grain interaction in the bond region under tensile loading. The work demonstrated that the diffusion bond remains intact and that tensile failure occurs in Ti-64 (i.e. the lower strength alloy) and is independent of the grain crystal orientation. The results from this study will provide materials engineers confidence in nesting FAST-DB technology in future near net shape manufacturing routes.

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

Pope

Violatos

et al. 2023

Metall Mater Trans A

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.