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In the present study, pre-deformation was applied to a metastable β titanium alloy (Ti-36Nb-2Ta-3Zr-0.35O) with the hope of improving its overall mechanical properties. The microstructural evolution and mechanical properties of the as-rolled alloys with different thickness reductions (from 4% to 35%) were characterized and analyzed. The results show that increasing the amount of pre-deformation can increase the strength (yield strength and tensile strength) of the Ti-36Nb-2Ta-3Zr-0.35O alloy without (4%–15% pre-deformation) or with only minor (23%–35% pre-deformation) sacrifice of ductility. Due to the increase of pre-deformation reduction, the β phase stability increases, leading to the twinning activities and the evolution of twinning system, which contribute to the strain hardening and the good ductility of the alloy pre-deformed by 9% and 15%. [ABSTRACT FROM AUTHOR]

Long-term exposure of structural materials to extreme hydrogen-enriched environments will lead to hydrogen embrittlement, and thus search and design of new alloys with economic and safety benefits against hydrogen embrittlement have become a top priority for the development of many engineering fields. In this work, the hydrogen embrittlement behavior of a new cobalt-free high-entropy alloy (HEA) Fe 27 Ni 28 Mn 27 Cr 18 was systematically studied and compared with a typical quaternary HEA Fe 25 Co 25 Cr 25 Ni 25. Numerous vacancies are produced in the process of electrochemical deuterium charging and the corresponding concentration is related with the solubility of deuterium atoms. Fe 27 Ni 28 Mn 27 Cr 18 has much higher concentrations of deuterium and vacancies than Fe 25 Co 25 Cr 25 Ni 25 , which is attributed to the Mn induced severe lattice distortion and results in different variations of mechanical properties. The ultimate tensile strength (UTS) of Fe 27 Ni 28 Mn 27 Cr 18 increases from 353.73 MPa to 589.50 MPa after electrochemical hydrogen charging while the elongation still remains at 74.73%, and its deformation mechanism is dominated by dislocation proliferation. In contrast, the UTS of hydrogen charged Fe 25 Co 25 Cr 25 Ni 25 decreases from 552.79 MPa to 501.53 MPa and the corresponding elongation also decreases from 74.65% to 67.24%, and the plastic deformation mechanism is dominated by twinning. This work demonstrates an economic cobalt-free HEA with great resistance to hydrogen embrittlement, which would enhance the applications of HEAs in hydrogen-enriched environments. • The severe lattice distortion in Fe 27 Ni 28 Mn 27 Cr 18 promotes the dissolution of deuterium atoms. • Deuterium charging leads to a decrease in the plasticity of the sample and an increase in the yield strength. • Fe 27 Ni 28 Mn 27 Cr 18 alloy has high plasticity and low hydrogen embrittlement susceptibility. [ABSTRACT FROM AUTHOR]