Fig. 1. True stress-strain compression curves of Ti-5553 heat-treated at 900 °C/1 h/Air Cooled (AC); (a) Dynamic compression performed by SHPB at different strain rates, And inset shows the elastic and strain hardening part of the curve (b) Quasi-static compression at the strain rate of ～10-3/s and strain hardening part of the curve is zoomed in and shown in the inset.

Fig. 2. EBSD images to notify phase transformation and mode of deformation (a) Heat-treated sample without any deformation, (b) Phase map of the sample without deformation, (c) deformed sample by compression, (d) Showing β and transformed α’’after compression.

Fig. 3. TEM analysis of Ti-5553 specimen before and after deformation; (a) Dark-field image which shows the presence of ωath athermal after air quenching from 900 °C. (b) Dark-field image illustrates ωD deformed after deformation. (c) and (d) Dark-field images of ωD deformed, which appeared in the slip band area. Dark-field images were taken along (-1010)ω whereas for SAED B//[011]β zone axes. Schematic images demonstrate the transformation to ωD deformed.

Fig. 4. OM analysis of deformed Ti-5553 samples; (a) High strain compression by SHPB having slip bands, twins and cross slips and also some disappearing cross slips mentioned in a white circle, (b) schematic of randomly arranged grains showing β unit cell and dense pack planes (110)? (blue) and (112)? (red), (c) Quasi-static compression image presenting slip bands in different grains and displaced grain boundaries (insets) after stress concentration (white circles).

Fig. 5. SEM and TEM analysis for slip bands after SHPB; (a) Normal (-110)? and cross (112)? slips present at the angle of 90° with respect to each other while zoom in inset illustrates the transformation of β to α’’ along with activation of slips & twins, and orientation of (-110)? and (112)? plane is shown in schematic, (b) slip bands pointed out by arrows, and transformation of β to α’’, and{332}? twins are shown in TEM and SAED pattern.

Fig. 6. SEM images after compression (a) slip bands, distortion of grains, spalling of grain boundary (inset), shear bands formation (inset) and the crack propagation along with shear band after quasi-static compression, (b) Stress concentration points (red circles), grain boundary displacing and cracking due to slip and overlapping of slip band with grain boundary (inset blue circle) at low strain rate compression, (c) Disappearance of slip band at grain boundary and GB cracking after high strain rate compression.

Fig. 7. HRTEM o Ti-5553 after compression (a) Stacking faults at the intersection point of twin or slips (b) nano cracking and twining.

Fig. 8. EBSD, SEM, and schematic representation of rotation of crystal after compressive loading; (a) Rotated crystal after twining having equal distance parallel slips, (b) (332) <113> primary and secondary twins and slips, (c) schematic representation of (a) shows the activation of a dense-pack plane (disoriented previously) rotated after twin, (d) changing of direction of slip bands (containing transformed α’’) while entering into the adjacent grain, (e) changing the direction of slips while intersecting with cross slip bands within the same grain, (f) Schematic representation of slip when passed through normal and deformed crystal, (g) (332) <113> twining (h, i) Martensitic transformation along with twins & slips, and rotation of the crystal.

Fig. 9. HRTEM and EBSD images showing stress-induced phase transformation after deformation;(a), (b) indicate the complete phase transformation from β to orthorhombic α’’, B//[010]α’’. (c), (d) are showing partially transformed α’’ from β, B//[111]β // [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]]α’’. (e), (f) Phase map showing matrix β, stress-induced α’’ and ω phase.

Fig. 10. HRTEM, SAED, and Schematic images after deformation; (a) Schematic atomic model showing ω transformation, (a1-a5) indicates the gradual transformation of β containing ωath to ωD upon loading. (b, d) describes the β, ωath and ωD (c) A linear fault schematic atomic model, sectioned through (101)? showing the transformation from β to ω after the displacement covered by an adjacent layer of atomic planes named as A & B and also showing the transformation by applying the wave of 2/3 < 111> longitudinal displacement to bcc atomic lattice, while bcc cube containing planes, is representing the transformation to complete (hexagonal) and incomplete (trigonal) ω phase by the displacement wave model.