In-situ investigation of phase transformations in ultra-fine grained Ti15Mo alloy

Phase Transformations upon Ageing in Ti15Mo Alloy Subjected to Two Different Deformation Methods

“…The formation of shear bands (areas with higher dislocation density) is typical in deformed alloys and can also cause an inhomogeneous precipitation of the α phase, as nucleation of the α phase is enhanced in areas with higher dislocation density [41]. This phenomenon has been described already in our previous studies [15][16][17] or in studies by other authors [18,20]. The growth of the α nuclei is diffusion-controlled and therefore is accelerated in the presence of a high density of dislocations as the pipe diffusion along dislocations is several orders of magnitude higher than the bulk diffusion [42].…”

“…The combination of intensive plastic deformation (such as SPD) and subsequent heat treatment leads to the precipitation of small, equiaxed and finely dispersed α precipitates, as reported in our previous studies [15][16][17] and in other studies [18,19]. Moreover, some authors previously reported improved strength of these deformed and aged metastable β-Ti alloys [19,20].…”

“…HPT straining results in the formation of a UFG structure of the Ti15Mo alloy [15,17,[29][30][31][32]. In the rudimentary stage of the HPT deformation, a twinning process takes place, which is followed by significant grain refinement [31,33,34].…”

“…In this study a metastable β-Ti alloy, Ti15Mo (in wt%) was investigated. The nondeformed (solution treated) condition contains a β matrix and metastable ω phase as it was reported in our previous study [15][16][17]. The material after solution treatment was deformed by high pressure torsion (HPT), which is a type of SPD method, and alternatively using cold-rotary swaging (RS).…”

Effect of the High-Pressure Torsion (HPT) and Subsequent Isothermal Annealing on the Phase Transformation in Biomedical Ti15Mo Alloy

“…In the specimen aged for a longer time (400 • C/16 h), nanometer-sized precipitates are seen in the SEM-BSE micrograph (note the higher magnification of this micrograph). These small ellipsoidal particles are particles of ω phase, which are visible due to chemical partitioning-ω phase particles are slightly Mo depleted [29]. Ageing at the higher temperature of 500 • C resulted in a precipitation of continuous and coarse α phase along grain boundaries (hereafter referred to as grain boundary α or GB α), which is also Mo depleted and appears as a long dark particle along the former β/β boundary (indicated by a yellow arrow).…”