This work studies the tension-compression asymmetry (TCA) of metastable austenitic stainless steel (MASS) in uniaxial loading depending on temperature. In-situ high-energy synchrotron X-ray diffraction was used to simultaneously probe phase fractions, transformation kinetics, crystallographic texture, lattice strains, strain and stress partitioning between austenite and martensites during quasistatic tensile and compressive deformation at 24°C, 60°C and 100°C. Complementary relaxed-constraint crystal plasticity simulations and calculations of the mechanical driving force related to the formation of α’ and ε martensites were performed. Transformation kinetics were analysed in relation to shear banding and the geometric alignment of ε lamellas depending on load sense and temperature.

Macroscopic stress-strain response and transformation behaviour exhibit weak TCA, with compression promoting the conversion of ε into α’. A strong TCA was found for crystallographic texture, bearing signatures of grain rotation due to plastic slip and of martensitic transformation (MT) in case of austenite (γ). Analysis of differently oriented austenite grain families also revealed a pronounced TCA of the lattice strains, linked to the γ → ε MT. This was found to be a direct consequence of driving force and volume change related to ε formation. Furthermore, stress is shared differently between austenite and martensites in tension vs. in compression. γ hardens more and hence carries a larger portion of the total stress in compression than in tension. These findings can help aid the development of new MASS material laws that are sensitive to load sense and temperature for advanced forming simulations.