On the effects of laser shock peening on fatigue behavior of V-notched AlSi10Mg manufactured by laser powder bed fusion

To study the abnormal failure of magnesium anodes for buried pipelines in marine engineering in the unique environment of mudflats, a strain of a sulfate–reducing prokaryote (SRP) was isolated from pipe–laying soil, and identified as Desulfovibrio sp. HQM3. Weight–loss test, electrochemical measurements, SEM, EDS, XRD, and CLSM techniques were used to study the effect of corrosion on the AZ31B magnesium alloy. Under the influence of SRP, the magnesium alloy corroded severely at rates up to 1.31 mm/year in the mudflat environment. SRP accelerated corrosion by 0.3mm/year. Pitting occurred on the samples in both abiotic and biotic systems. The pitting depth reached 163.47 μm in the biotic system after 14 days. The main composition of a petal–like corrosion product was Mg(OH)2. The results show that a mudflat environment can lead to an accelerated corrosion of magnesium alloys.

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Corrosion of an AZ31B Magnesium Alloy by Sulfate-Reducing Prokaryotes in a Mudflat Environment

Friction stir welding (FSW) of CuCrZr sheets was performed and Laser Shock Peening (LSP) was carried out as a post-weld surface treatment. Effect of LSP on hardness, tensile and fatigue strength was investigated. Depth of compressive residual stress in base material increased from 550 μm to 700 μm when the number of LSP shots was increased from one to five. However, noticeable change in surface residual stress could not be observed which is attributed to the saturation of dislocation density or plastic deformation at the surface. An increase in yield strength up to ∼35% as well as an improvement in the fatigue life up to ∼70% after LSP could be achieved for base and FSW specimens. Increase in low angle grain boundaries after LSP indicates the increase in substructure induced by plastic deformation. A quantitative analysis using grain boundary misorientation and kernel average misorientation was used to understand microstructural changes due to the LSP and correlate it with the mechanical properties. 

Effect of Laser Shock Peening on micro-structure and mechanical properties of Friction Stir Welded CuCrZr sheets

Friction stir welding (FSW) of CuCrZr sheets was performed and Laser Shock Peening (LSP) was carried out as a post-weld surface treatment. Effect of LSP on hardness, tensile and fatigue strength was investigated. Depth of compressive residual stress in base material increased from 550 μm to 700 μm when the number of LSP shots was increased from one to five. However, noticeable change in surface residual stress could not be observed which is attributed to the saturation of dislocation density or plastic deformation at the surface. An increase in yield strength up to ∼35% as well as an improvement in the fatigue life up to ∼70% after LSP could be achieved for base and FSW specimens. Increase in low angle grain boundaries after LSP indicates the increase in substructure induced by plastic deformation. A quantitative analysis using grain boundary misorientation and kernel average misorientation was used to understand microstructural changes due to the LSP and correlate it with the mechanical properties.

Jiajun Wu

Papers

Microstructural response and improving surface mechanical properties of pure copper subjected to laser shock peening

Nanosecond pulsed laser-assisted modified copper surface structure: Enhanced surface microhardness and microbial corrosion resistance