In this work, the impact of the microstructure and the loading conditions on the mechanical behavior of a brich Ti17 titanium alloy is investigated. For this purpose, two different initial microstructures are considered : (i) a two-phase lamellar a ? b microstructure and (ii) a single-phase equiaxed b-treated microstructure. First, compression tests are performed at different strain rates (from 10 À1 to 10 s-1) and different temperatures (from 25 to 900 C) for both microstructures. Then, optical microscopy, scanning electron microscopy, EBSD and X-ray diffraction analyses of deformed specimens are carried out. Whatever the loading conditions are, the flow stress of the as-received a ? b Ti17 is higher than that of the b-treated Ti17. Also, because of a higher strain-rate sensitivity, the b-treated Ti17 is less prone to shear banding. At low temperatures (i.e., T 450 C), the deformation behavior of both the as-received a ? b and the b-treated Ti17 is controlled by strain hardening. For the b-treated Ti17 alloy, martensitic transformation is systematically detected in this temperature range. The softening behavior of the as-received a ? b Ti17 observed at high temperatures is due to the joint effect of dynamic recrystallization, dynamic transformation , adiabatic heating and morphological texture evolution. For the b-treated Ti17 alloy, when the temperature exceeds 700 C, stressstrain curves display a yield drop phenomenon, which is explained by dynamic recrystallization.

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of β-Ti42Nb alloy. Compression tests are performed under two strain rates (1 s−1 and 10 s−1) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45∘ exhibit higher flow stress than those produced with a building direction of 90∘, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV0.1. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.