Phase transformation kinetics during continuous heating of and metastable titanium alloys

The effect of heating rate on the phase trans-formation kinetics of a Ti–10V–2Fe–3Al metastable btitanium alloy quenched from the b field is investigated byfast in situ high energy synchrotron X-ray diffraction anddifferential scanning calorimetry. The initial microstructureis formed by a00 martensite and finexath particles distrib-uted in the retained b-phase matrix. The phase transfor-mation sequence varies with the heating rate as revealed byanalysis of the continuous evolution of crystallographicrelationships between phases. At low temperatures anathermal reversion of a00 martensite into b takes place. Thisreversion occurs to a larger extent with increasing heatingrate. On the other hand, diffusion–driven precipitation andgrowth of the x phase is observed for lower heating ratesaccompanying the reverse martensitic transformation.Furthermore, the results show that the stable a phase canform through three different paths: (a) from the x phase,(b) from a00 martensite, and (c) from the b phase.Introduction Metastable b titanium alloys are mostly used in a widerange of components for the aerospace industry and asalternative structural materials for the automotive sectordue to their high specific strength and excellent fatigueresistance [1, 2]. Moreover, biomedical applications arealso being considered due to biocompatibility of b-Tialloys and partial or total superelasticity [3]. Themechanical properties of these alloys for structural appli-cations are basically defined by a homogeneous distribu-tion of a/b interfaces due to the presence of fine aprecipitates embedded in a b matrix [4]. On the other hand,the superelastic behavior is associated to a reverse mar-tensitic transformation that leads to shape memory effect[5]. The formation of the a phase, its morphology, volumefraction, size, distribution as well as the progression ofeventual shape memory effect are influenced by the phasetransformation kinetics during heat treatments [6]. There-fore, a correct understanding of these processes is requiredfor the optimization of the heat treatment and chemicalcomposition of the alloys. In most of the prior works theElectronic supplementary material The online version of thisarticle (doi:10.1007/s10853-014-8701-6) contains supplementarymaterial, which is available to authorized users. P. Barriobero-Vila (&) G. Requena F. WarchomickaInstitute of Materials Science and Technology, ViennaUniversity of Technology, Karlsplatz 13/308, 1040 Vienna,Austriae-mail: [email protected]. Requenae-mail: [email protected]. Warchomickae-mail: [email protected] F. WarchomickaInstitute for Materials Science and Welding, Graz University ofTechnology, Kopernikusgasse 24, 8010 Graz, AustriaA. Stark N. SchellHelmholtz-Zentrum Geesthacht, Centre for Materials andCoastal Research, Max-Planck-Str. 1, 21502 Geesthacht,Germanye-mail: [email protected]. Schelle-mail: [email protected] T. BuslapsID15, European Synchrotron Radiation Facility,Rue J. Horowitz, 38042 Grenoble, Francee-mail: [email protected] 123J Mater Sci (2015) 50:1412–1426DOI 10.1007/s10853-014-8701-6