The application of biodegradable magnesium-based materials in the biomedical field is highly restricted by their low fatigue strength and high corrosion rate in biological environments. Considering the sensitivity of both fatigue strength and corrosion rate to the surface characteristics of the material, apposite surface treatments could address these challenges. As a low cost and versatile severe plastic deformation technique aimed at inducing surface grain refinement, severe shot peening has been effective in enhancing mechanical properties and promoting cellular interactions on non-degradable biocompatible metallic materials. Herein, we treated the surface of a biocompatible magnesium alloy AZ31 by severe shot peening in order to evaluate the potential of surface grain refinement to enhance its functionality in a biological environment. The AZ31 samples were studied in terms of a wide variety of micro/nanostructural, mechanical, and chemical characteristics in addition to cytocompatibility properties. The evolution of surface grain structure and surface morphology were investigated using optical as well as scanning and transmission electron microscopy. Surface roughness, wettability and chemical composition, as well as in depth-microhardness and residual stress distribution, and corrosion resistance were investigated. Successive light surface grinding was used after severe shot peening to eliminate the effect of surface roughness and separately investigate the influence of grain refinement alone. Cytocompatibility tests with osteoblasts (or bone forming cells) were performed using sample extracts. Results revealed for the first time that severe shot peening can significantly enhance mechanical properties without causing adverse effects to the growth of surrounding osteoblasts. The corrosion behavior, on the other hand, was not improved by severe shot peening; nevertheless, slight grinding of the rough surface layer with a high density of crystallographic lattice defects, without removing the entire nanocrystallized layer, provided a good potential for improving corrosion characteristics after severe shot peening and thus, this method should be studied for a wide range of orthopedic applications in which biodegradable magnesium is used.

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Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO3)2, 0.06 M NH4H2PO4 and 10 ml l(-1) of H2O2. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process.

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Ultrasonic impact peening was applied on welded joints manufactured from Strenx 700 MC high strength low alloy steel with the aim to improve the fatigue properties. Three different surface treatment parameters were tested, which resulted in transformation of the near-surface tensile residual stresses in the weld metal and heat affected zone to compressive residual stress field, while maximal values from −400 MPa up to −800 MPa were reached. The highest fatigue life improvement was reached by the double peening with the 85 N contact force, where the fatigue limit for N = 108 cycles increased from 370 MPa to 410 MPa.

Equal channel angular pressing (ECAP) is used to investigate the influence of microstructural evolution on mechanical properties and corrosion resistance of an extruded Mg alloy (ZFW MP) via route BC at 579 K. The transmission electron microscope (TEM) and the optical microscope (OM) are used to observe the microstructure. Tensile testing and hardness measurement are used to investigate the mechanical properties at room temperature, and electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements are used to examine the corrosion properties in Hank's solution at 37 °C. The ECAPed samples show the enhanced mechanical properties as compared with the extruded sample. The ECAPed ZFW MP alloy possesses a homogeneous microstructure due to dynamic recrystallization (DRX), as indicated by the resulting microstructures. However, the electrochemical measurements show that a reduction in the corrosion resistance is caused by the ECAP processing. A broader grain size distribution and a continuous network of the oxide layers along grain boundaries result in an improvement in the corrosion resistance in the extruded sample as compared with the ECAPed sample. However, better mechanical properties are observed with a further homogeneous microstructure in the ECAPed sample as compared with the extruded counterpart.

This study aims to evaluate and compare the mechanical and corrosion resistance properties of ultrafine-grained (UFG) copper with that of coarse-grained (CG) copper microstructures. Ultrafinegrained microstructures are produced through severe plastic deformation using rotary swaging. Potentiodynamic polarization and electrochemical impedance tests are performed at 37 C in Hank's solution as the simulated body fluid. The results reveal that the highly deformed UFG-materials not only show marked enhancement of the mechanical properties but also remarkable enhancement of corrosion resistance compared with that of the CG counterpart.