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To obtain ideal implant materials, we hot extruded Mg-2.0Zn-0.5Zr-3.0Gd solid-solution alloys, and studied extrusion temperature impacts on materials properties. Fine dynamic recrystallized (DRXed) grains (∼5 μm) and elongated coarse un-dynamic recrystallized (unDRXed) deformed grains turned out at the range of 470–490 °C, but changed to bigger ones (∼8 μm) and abnormal growth (30–40 μm) at 490–510 °C. Precipitated phases consist of rod-like (Mg, Zn) 3 Gd particles and newly precipitated Mg 2 Zn 11 rectangles. The alloy extruded at 490 °C meets all mechanical and anticorrosive requirements for biomaterials, thanks to evenly distributed second phases via the solid solution, and the grain refinements through the hot extrusion. [ABSTRACT FROM AUTHOR]

Microstructure evolution and mechanical properties of AISI 316 LN austenitic stainless steel (SS) after cryorolling with different strains were investigated by means of optical, scanning and transmission electron microscopy, X-ray diffractometer, microhardness tester, and tensile testing system. The deformation-induced martensite transition and the deformation microstructure occurred during cryorolling process were always composed of high-density dislocations, deformation twins, and deformation-induced martensites. Following the strain, the dislocation density in deformation microstructure approached saturation state and the volume fraction of deformation twins combined with deformation-induced martensites increased significantly. At the 70% strain, original austenite was transformed into martensite completely. Further increasing the strain to 90% would refine the martensitic lamellae to nanoscale. The deformation degree also led to remarkable increase of the strength and hardness of the cryorolled SS, and drastic reductions of the elongation. Due to the cryorolling, the tensile fracture morphology changed from typical ductile rupture to a mixture of quasi-cleavage and ductile fracture. [ABSTRACT FROM AUTHOR]

Supersonic fine particles bombarding (SFPB) technology opens a new territory for engineering materials towards improved performances. Owing to its merits and emerging applications, 300M steel (tensile strength ≥1800 MPa) was treated with SFPB to create surface gradient nanostructures. The time dependent SFPB process was implemented on various 300M steel surface to investigate the microstructural evolution and mechanical property. 300M steel surface grains were sufficiently refined down to nanometer scale under high energy SFPB. In the subsurface layer, acicular martensite was found to be bent and broken, resulting in the high-density dislocation. At the early stage of SFPB, the impact affected area of 300M steel surface was deepened with increasing SFPB time, and the grains were constantly refined, which further lead to higher strength and improved hardness. However, after longer treatments of more than 90 s, bombardment energy accumulated at 300M steel surface resulted in grain growths and deteriorations of hardness. In particular, the newly formed microcracks substantially reduced the tensile strength. After SFPB treatment, the dimple size of the 300M steel surface fracture decreased significantly, and a large area of cleavage plane appeared, showing typical characteristics of ductile-brittle mixed fracture. • Surface gradient nanostructures of 300M steel has been created by SFPB treatment. • Dislocation motion has been found the dominant nano-crystallization mechanism. • Appropriate SFPB time can improve the mechanical properties of 300 M steel. • Mixed ductile-brittle fracture morphology was observed for SFPB treated 300 M steel. [ABSTRACT FROM AUTHOR]

Controlled cold rolling impacts on microstructure and mechanical properties of the rare earth Ce-modified SAF 2507 super duplex stainless steel (SDSS) are investigated towards a better application and development prospective over the pristine SDSS. Rolling was performed at room temperature with the deformation level in a range of 30%–90%. A large amount of dislocations into the ferrite phase turned out, and their density increased with the deformation. While, emergence of dislocation plugs group, ferrite grains get refined to nanometer scale during the deformation process. In addition to deformed bands within austenite, formation of α′-martensitic phases and significant increment in their volume fraction are detected and attributed to deformation-induced martensitic transformation. Elongation of the ferrite and austenite microstructures along the deformation direction under the action of high strain also resulted in fibers formation gradually. Correspondingly, significant increase in the strength index while decrement in the plasticity index are observed. Moreover, cold rolling deformation not only affects the tensile fracture morphology but also switches it from a typical ductile to a ductile and quasi-cleavage mixed fracture. [ABSTRACT FROM AUTHOR]