New Lower Temperature Superplastic Titanium Sheet Alloy

Currently, superplastic forming (SPF) of Ti-6Al-4V sheet is in most cases performed at temperatures above 1600F. Lower temperature SPF, although providing for significant reduction of the forming process costs, requires sheet material with improved SPF properties. Grain size reduction has proved to enable forming at lower temperatures; however, stable production of submicron grain sheet in a production environment remains an expensive process, which in many cases counterweighs the advantages of low temperature forming.

A new titanium sheet alloy, developed jointly by Boeing and VSMPO-Avisma, can be superplastically formed at both standard and low SPF temperatures, providing for formability and mechanical properties similar to those of fine-grained Ti-6Al-4V sheet. Such performance does not require special thermomechanical processing to achieve a submicron grain size, but rather, results from the chemical composition. This allows for a higher volume fraction of beta phase at deformation temperatures as well as higher fraction of alpha/beta interphase boundaries promoting grain boundary slip.

The presentation covers the considerations of development of the chemical composition to achieve lower flow stress levels and better strain uniformity in different directions, some results of testing and evaluation of the new alloy material and potential implementation plans.