Microstructure and surface texture driven improvement in in-vitro response of laser surface processed AZ31B magnesium alloy

The present work explored effects of laser surface melting on microstructure and surface topography evolution in AZ31B magnesium alloy.Thermokinetic effects experienced by the material during laser surface melting were simulated using a multiphysics finite element model.Microstructure and phase evolution were examined using scanning electron microscopy,X-ray diffraction,and electron back scatter diffraction.Surface topography was evaluated using white light interferometry.The interaction of surface melted samples with simulated body fluid was monitored by contact angle measurements and immersion studies up to 7 days.Laser surface melting led to formation of a refined microstructure with predominantly basal crystallographic texture.Concurrently,the amount ofβphase(Mg_(17)Al_(12))increased with an increase in the laser fluence.βphase preferentially decorated the cell boundaries.In terms of topography,the surface became progressively rougher with an increase in laser fluence.As a result,upon immersion in simulated body fluid,the laser surface melted samples showed an improved wettability,corrosion resistance,and precipitation of mineral having composition closer to the hydroxyapatite bone mineral compared to the untreated sample.

Simulation and experimental analysis of melt pool evolution in laser engineered net shaping

In this work,the evolution of melt pool under single-point and single-line printing in the laser engineered net shaping(LENS)process is analyzed.Firstly,the basic structure of the melt pool model of the LENS process is established and the necessary assumptions are made.Then,the establishment process of the multi-physical field model of the melt pool is introduced in detail.It is concluded that the simulation model results are highly consistent with the online measurement experiment results in terms of melt pool profile,space temperature gradient,and time temperature gradient.Meanwhile,some parameters,such as the 3D morphology and surface fluid field of the melt pool,which are not obtained in the online measurement experiment,are analyzed.Finally,the influence of changing the scanning speed on the profile,peak temperature,and temperature gradient of the single-line melt pool is also analyzed,and the following conclusions are obtained:With the increase in scanning speed,the profile of the melt pool gradually becomes slender;The relationship between peak temperature and scanning speed is approximately linear in a certain speed range;The space temperature gradient at the tail of the melt pool under different scanning speeds hardly changes with the scanning speed,and the time temperature gradient at the tail of the melt pool is in direct proportion to the scanning speed.

Surface engineering and the application of laser-based processes to stents-A review of the latest development

Late in-stent thrombus and restenosis still represent two major challenges in stents’design.Surface treatment of stent is attracting attention due to the increasing importance of stenting intervention for coronary artery diseases.Several surface engineering techniques have been utilised to improve the biological response in vivo on a wide range of biomedical devices.As a tailorable,precise,and ultra-fast process,laser surface engineering offers the potential to treat stent materials and fabricate various 3D textures,including grooves,pillars,nanowires,porous and freeform structures,while also modifying surface chemistry through nitridation,oxidation and coatings.Laser-based processes can reduce the biodegradable materials’degradation rate,offering many advantages to improve stents’performance,such as increased endothelialisation rate,prohibition of SMC proliferation,reduced platelet adhesion and controlled corrosion and degradation.Nowadays,adequate research has been conducted on laser surface texturing and surface chemistry modification.Laser texturing on commercial stents has been also investigated and a promotion of performance of laser-textured stents has been proved.In this critical review,the influence of surface texture and surface chemistry on stents performance is firstly reviewed to understand the surface characteristics of stents required to facilitate cellular response.This is followed by the explicit illustration of laser surface engineering of stents and/or related materials.Laser induced periodic surface structure(LIPSS)on stent materials is then explored,and finally the application of laser surface modification techniques on latest generation of stent devices is highlighted to provide future trends and research direction on laser surface engineering of stents.

The 3rd International Symposium on High Power Laser Science and Engineering

9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),

Laser diode corner pumped Nd：KGW slab laser

This paper reports the continuous wave （CW） and Q-switched operation of a diode pumped KGd （WO4）： Nd （Nd：KGW） slab laser with a comer pumped geometry at the wavelength of 1067 nm. With an optical conversion efficiency of 38% and 34%, average powers of 23 and 20 W in CW and Q-switched modes were achieved respec- tively. The maximum pulse energy of 27 mJ was observed with a repetition rate of 840 Hz.