Modelling of phase transformation kinetics in Ti alloys – Isothermal treatments

Abstract

We have developed a model which is able to describe the formation of high temperature microstructures in β metastable titanium alloys. It is based on the classical theory of nucleation, and on growth laws obtained by assuming that the processes are controlled by the diffusion of the alloying chemical species only. Two morphologies are described: grain boundary allotriomorphs, and Widmanstätten plates gathered in colonies growing from the allotriomorphs. Moreover, a statistical description of the nucleation conditions on β grain boundaries has been introduced in order to obtain the global kinetics of the transformation. The model predictions proved to be in good agreement with experimental results.

Microstructure and Mechanical Properties of Gas-Tungsten-Arc–Welded Ti-15-3 Beta Titanium Alloy

“…[20] The appearance of a WGB involves the nucleation of a precipitate crystal with a composition different from that of the matrix, at the interphase boundary of another crystal of the same phase. This observation made in b-CEZ [19] and other b-Ti alloys such as Ti-6.6 at. pct Cr and Ti-8.6 at.…”

“…[18] Solutionizing and aging results in a precipitation within the b grains. [19,20] The morphology of the a phase is influenced by the aging temperature, duration, and amount of a stabilizers present in the alloy. The morphology, size, and distribution of these precipitates affect the mechanical properties of the alloy.…”

Tuning the stress induced martensitic formation in titanium alloys by alloy design

“…According to earlier results [26,27], the a phase composition does not vary much with the present heat-treatment conditions in the two phase region. Therefore two typical samples, (one for Ti-10V-2Cr-3Al alloy, another for Ti-10V-1Fe-3Al alloy) were chosen for a composition analysis with EPMA.…”

A model for Ti–6Al–4V microstructure evolution for arbitrary temperature changes

“…The alloying chemical species' composition, mainly Aluminium and Vanadium, of the phases varies during their formation. This is influencing the kinetics of the phase transformations and the morphologies that are formed; Appolaire et al (2005) have modelled the phase formation using the diffusion of the alloying chemical species. Vanadium and Aluminium are in the case of Ti-6Al-4V the elements of interest.…”