The impacts of rolling temperature on phase transformations and mechanical properties were investigated for AISI 316LN austenitic stainless steel subjected to rolling at cryogenic and room temperatures. The microstructure evolution and the mechanical properties were investigated by means of optical, scanning, and transmission electron microscopy, an X-ray diffractometer, microhardness tester, and tensile testing system. Results showed that strain-induced martensitic transformation occurred at both deformation temperatures, and the martensite volume fraction increased with the deformation. Compared with room temperature rolling, cryorolling substantially enhanced the martensite transformation rate. At 50% deformation, it yielded the same fraction as the room temperature counterpart at 90% strain, while at 70%, it totally transformed the austenite to martensite. The strength and hardness of the stainless steel increased remarkably with the deformation, but the corresponding elongation decreased dramatically. Meanwhile, the tensile fracture morphology changed from a typical ductile rupture to a mixture of ductile and quasi-cleavage fracture. The phase transformation and deformation mechanisms differed at two temperatures, with the martensite deformation contributing to the former, and austenite deformation to the latter. Orientations between the transformed martensite and its parent phase followed the K–S (Kurdjumov–Sachs) relationship.

Fatigue resistance, particularly the endurance limit, is an important design consideration in engineering applications for TiZr-based alloys. The investigated Ti–20Zr–6Al–4 V (wt-%) alloy exhibited a high fatigue endurance limit of 775 MPa. Results showed that severe local stress concentration due to extensive dislocation pile-up at α/β interfaces was responsible for the crack initiation. A transition from a tensile mode to a shear mode crack was observed during crack propagation. Many striations as well as some micro-cracks which can improve the resistance to crack propagation exist in the stable crack-propagation region. A localised deviation between the crack-growth direction was also found, and this outcome combined with micro-cracks and tear ridge may be attributed to varied crystallographic orientations between different phases.