Investigation of early stage deformation mechanisms in a metastable β titanium alloy showing combined twinning-induced plasticity and transformation-induced plasticity effects

Abstract

International audienceAs expected from the alloy design procedure, combined Twinning Induced Plasticity (TWIP) and Transformation Induced Plasticity (TRIP) effects are activated in a metastable β Ti-12(wt.%)Mo alloy. In-situ Synchrotron X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations were carried out to investigate the deformation mechanisms and microstructure evolution sequence. In the early deformation stage, primary strain/stress induced phase transformations (β->ω and β->α'') and primary mechanical twinning ({332}<113> and {112}<111>) are simultaneously activated. Secondary martensitic phase transformation and secondary mechanical twinning are then triggered in the twinned β zones. The {332}<113> twinning and the subsequence secondary mechanisms dominate the early stage deformation process. The evolution of the deformation microstructure results in a high strain hardening rate (~2GPa) bringing about high tensile strength (~1GPa) and large uniform elongation (> 0.38)

Design and tensile properties of a bcc Ti-rich high-entropy alloy with transformation-induced plasticity

“…[16,18,23,24] As expected from the chosen alloying design, cyclic stress-strain curves display a double yielding behavior (detailed in Figure 1(b) of the Supplementary material), typically observed in metastable β-alloys. [25,26] This behavior is reflected in the evolution of the normalized work-hardening rate (θ/G, θ = dσ T /dε p ), with the shear modulus G estimated from G/E = 3/8 as experimentally found for polycrystalline metallic materials. [27] Three stages as visible in Figure 2 (green curve): first, a classical decrease in θ/G until ε p = 0.018 (stage 1), then an increase in θ /G in stage 2 up to a maximum of about θ /G = 0.103 and finally a decrease from ε p = 0.07 to the end.…”

Formation of Deformation-Induced Products in a Metastable-β Titanium Alloy during High Temperature Compression

“…In this study, two kinds of ω phase were noticed: (1) nanosized spherical or ellipsoidal particles (ω ath ) (Figure 5d) that have been observed to occur on accelerated cooling in metastable-β titanium alloys [18,20,38] and (2) lamellae ω (stress-induced ω) (Figure 5c) which has been reported in titanium alloys after plastic deformation [23,44,45]. Shuffle of atoms in {112} β planes in the direction of 111 has been suggested as the formation mechanism for both ω types [44].…”

“…%) [21], β-Cez alloy [22] and Ti-12 Mo (wt. %) [23,24]. Depending on the beta phase stability and stress conditions (strain rate, strain path, etc.…”

Microstructures and mechanical properties of as‐cast titanium–zirconium–molybdenum ternary alloys

“…For a metal to be used as a biomaterial, high ductility is desirable to minimize the risk of breakage. The b-type titanium alloys were found to possess higher ductility than a-type titanium alloys because a range of deformation modes including phase transformation, twinning, and/or dislocation slip can be activated simultaneously during deformation [15][16][17][18]. Hence, adding b-phase stability elements, such as iron, tantalum, niobium, and molybdenum, to the binary titanium-zirconium alloy to obtain b-type titanium alloys may be a viable way to improve the ductility.…”