Alloy design by tailoring phase stability in commercial Ti alloys

• The mechanical characteristics and the operative deformation mechanisms of a metallic alloy can be optimised by explicitly controlling phase stability. Here an integrated thermoelastic and pseudoelastic model is presented to evaluate the beta stability in Ti alloys. The energy landscape of beta ->alpha ' /alpha '' martensitic transformation was expressed in terms of the dilatational and transformational strain energy, the Gibbs free energy change, the external mechanical work as well as the internal frictional resistance. To test the model, new alloys were developed by tailoring two base alloys, Ti-6Al-4V and Ti-6Al-7Nb, with the addition of beta-stabilising element Mo. The alloys exhibited versatile mechanical behaviours with enhanced plasticity. Martensitic nucleation and growth was fundamentally dominated by the competition between elastic strain energy and chemical driving force, where the latter term tends to lower the transformational energy barrier. The model incorporates thermodynamics and micromechanics to quantitatively investigate the threshold energy for operating transformation-induced plasticity and further guides alloy design.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Annan materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Other Materials Engineering (hsv//eng)

Nyckelord

Ti alloys

Physical modelling

Alloy design

Phase transformation

Plasticity

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)