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Highlights: [•] Secondary phase evolution caused by laser processing was firstly reported. [•] Microstructure development was controlled by heat flow thermodynamics and kinetics. [•] Solid-state transformation resulted in submicron and nano-scale precipitates. [•] Cluster-shaped particles in overlapped region were due to precipitation coarsening. [•] Properties of materials can be tailored selectively by laser processing. [ABSTRACT FROM AUTHOR]

Abstract: Laser-induced darkening effect is an important phenomenon for Mg alloys to provide potential engineering applications in product identification, photocatalysts, and bio-optical implants. This work reports darkening evolution on Mg alloy by KrF excimer laser irradiation. Effort was made to study how processing environment influence morphological evolution and chemical variation of laser-irradiated surface. All irradiated surfaces were characterized using Talysurf surface profiler, atomic force microscope, scanning electron microscope and energy dispersive X-ray spectrometer. The results showed that oxygen content played a critical role in determining darkening effect on the Mg alloy, and surface morphology transferred from network structures to granular structures and protruding oxide particles when darkening occurred. Mechanism of laser-induced darkening in Mg alloy was further discussed. [Copyright &y& Elsevier]

Abstract: Laser surface melting (LSM) is known to enhance the wear and corrosion resistance of Mg alloys, but its effect on microstructural evolution of Mg alloys is not well understood. An effort has been made to study the effect of rapid solidification following LSM on the microstructural evolution of AZ91D Mg alloy. The results of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy indicated that the solidification microstructure in the laser-melted zone was mainly cellular/dendrite structure of primarily α-Mg phase and continuous network of β-Mg17Al12 phase. Numerical prediction of the laser-melted zone suggested that cooling rates increased strongly from the bottom to the top surface in the irradiated regions. An attempt has been made to correlate dendrite cell sizes of the solidification microstructure with the cooling rates in the laser-treated AZ91D Mg alloy. [Copyright &y& Elsevier]

We investigate the onset of detwinning in magnesium alloy Mg-3Al-1Zn under continuous loading with real-time in situ synchrotron X-ray diffraction. Detwinning of the { 10 1 ¯ 2 } extension twins activated both by tension parallel to and compression perpendicular to the c -axis fibers is explored. The experimental results reveal that detwinning of the { 10 1 ¯ 2 } extension twins occurs immediately upon unloading, regardless of whether the twins are activated by tension parallel to or compression perpendicular to the c -axis fibers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Permanent darkening effect was achieved on Mg alloy surface following by nanosecond pulse Nd:YAG laser irradiation in atmosphere environment. [•] Different from darkening effect caused by oxidation previously, surface structure plays an important role in current work. [•] Darkening surface is uniform over spectral range from 200nm to 1100nm. [•] Surface morphology of darkening areas contains of cauliflower-like clusters and protruding particles. [•] Formation of clusters and particles was mainly due to hydrodynamic ablation during laser processing. [ABSTRACT FROM AUTHOR]

We investigate deformation dynamics in a textured magnesium alloy under uniaxial tension and compression along two different directions. The loading axis (LA) is either parallel or perpendicular to the normal direction (ND), referred to as LA ∥ ND tension/compression and LA ⊥ ND tension/compression, respectively. Stress − strain curves are measured simultaneously with X-ray diffraction and strain field mapping via synchrotron X-ray digital image correlation. Massive { 10 1 ̄ 2 } extension twins are observed in the LA ∥ ND tension and LA ⊥ ND compression specimens. The growth rate of tension-induced twins is lower than that of compression-induced twins, likely because the pyramidal 〈 c + a 〉 slips accommodate partial deformation along the c -axis in the LA ∥ ND tension specimen. Both the tension- and compression-induced deformation twins can slow down the process of strain localization, and thus an increase in strain hardening rate as well as the anisotropy in plastic deformation. The plastic strain ratios depend on strain localization and the relative orientation of the loading direction with respect to the basal texture, and are much larger in tension than in compression. [ABSTRACT FROM AUTHOR]