Modeling of the effect of the β phase deformation on the α phase precipitation in near-β titanium alloys

Abstract

To cite this version:Julien da Costa Teixeira, Benoît Appolaire, Elisabeth Aeby-Gautier, Sabine Denis, Fabien Bruneseaux. Modeling of the effect of the beta phase deformation on the alpha phase precipitation in near-beta titanium alloys. Acta Materialia, Elsevier, 2006, 54, pp. AbstractA model has been developed in order to describe the influence of a prior plastic deformation of the β phase above the transus on the precipitation of the α phase occurring during a subsequent cooling. The model relies on the calculation of the nucleation and growth rates of the α precipitates at the grain boundaries, based on a model presented formerly. Two major modifications have been carried out: first, the geometrical representation of the β microstructure accounts for subgrains resulting from the deformation process; second, the calculation of the nucleation rate is dependent on the conditions of the plastic deformation. A careful analysis of the main parameters of the model has led to distinguish between several assumptions: the Widmanstätten colonies are likely to cross the subgrains during their growth; and the critical width of the transition from the allotriomorphs to the Widmanstätten plates is likely to decrease when the misorientation angle of the grain boundary decreases. Calculations performed for assessing the influence of the strain and strain rate on the transformation kinetics are in good agreement with previous measurements.

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

“…The a phase is expected to nucleate at b grain boundaries (a GB ) and grow normal to the grain boundary to a critical width beyond which Widmansta¨t-ten plates of the a phase (a WGB ) nucleate sympathetically and grow inward. [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.…”

“…[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.…”

Elastically mediated interactions between grain boundaries and precipitates in two-phase coherent solids

“…For example, in Ni-Al superalloys, γ precipitates in the vicinity of GBs have been shown to be responsible for GB serration, leading to improved mechanical properties at high temperature 14,15 . In addition, in steel and Ti-based alloys submitted to thermo-mechanical treatments, acicular Widmanstätten precipitates, are observed to grow from the GBs in a direction normal to the GB plane 16,17 . While the stationary growth kinetics of these structures have been recently clarified 18 , the initial stage of growth that involves the nucleation of precipitates along the GBs is not understood.…”

Modeling ultrasonic noise and attenuation in elongated duplex polycrystalline materials

“…An experimental micrographic picture where a duplex structure appears clearly is given by [9]. For modeling purposes, we describe that structure as a mix of primary and secondary phase in a manner similar to [8].…”

“…By using equation (9) in equation (3), we can obtain a decomposition of the scattering coefficient of a duplex microstructure into three scattering coefficients. The three coefficients of this decomposition are the scattering coefficients of three fictitious materials characterized by spatial correlation functions and elastic constants given in table 3.…”