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Laser surface melting (LSM) with alternating magnetic field was applied to the AZ91D magnesium alloy using a 2 kW fiber laser. The microstructure and phase composition of melted layer with and without alternating magnetic field were studied by optical microscopy (OM) and X-ray diffraction (XRD) measurement. The micro-and nano-hardness, wear and corrosion resistance of the modified layers and as-received magnesium alloy were measured by microhardness tester, nanoindenter, pin-on-disc wear tester and electrochemical workstation, respectively. Results showed that the LSM treatment resulted in a highly homogeneous modified layer with refined grains. Compared to the melted layer without electromagnetic stirring (EMS), the microstructure of melted layer became finer and more uniform, the dendritic crystal was changed to an approximately equiaxial crystal under the action of EMS application treatment. The microhardness of the melted layer with and without EMS (70.8Hv0.1 and 62.9Hv0.1) is higher than the as-received magnesium (55.53Hv0.1) microhardness, regarding especially the melted layer with EMS.·The friction coefficient and wear mass loss of the melted layer with EMS were 0.2175 and 0.1616 g accordingly, subsequently having decreased by 14.8% and 6.1% compared to the melted layer without EMS. From the worn-out appearance of the melted layer without and with EMS, the wear mechanism turning from a slight abrasive wear into a slight plastic deformation during EMS-assisted. The corrosion potential and corrosion current density of the melted layer with EMS were increased by 18.7% and decreased by 4% compared to the corresponding effects without the EMS-assisted, respectively. Experimental results showed that the melted layer assisted by EMS displayed the best wear and corrosion resistance properties.

Transient temperature field distribution is important for quality control of laser sintering graphene (Gr) reinforced nickel matrix (Ni-Gr) nanocomposites and the optimization of sintering parameters. To date, it is difficult to measure the temperature field directly. Thus, numerical simulation was utilized to study the distribution and evolution of temperature field. Finite element models were employed to simulate the sintering process of Ni-Gr coatings on AISI 4140 steel. The temperature distribution, the depth of the melting pool, the width of metallurgical bonding and the parameter optimizing method for laser sintering were investigated. In order to verify simulation results, single-track experiments were performed with the same laser sintering parameters as simulation. Simulated results reveal that convection and radiation heat transfer, and the latent heat of phase transition play a major role in the sintering process. Simulation output is consistent with experiments under the same processing parameters. Based on simulation results, substrate melting depth, metallurgical bonding width and thermal accumulation effects can be predicted. Thus, according to these guidelines, the optimal laser sintering parameters can be decided.

Numerous quantitative trait loci (QTL) have been mapped in tetraploid and hexaploid wheat and wheat relatives, mostly with simple sequence repeat (SSR) or single nucleotide polymorphism (SNP) markers. To conduct meta-analysis of QTL requires projecting them onto a common genomic framework, either a consensus genetic map or genomic sequence. The latter strategy is pursued here. Of 774 QTL mapped in wheat and wheat relatives found in the literature, 585 (75.6%) were successfully projected onto the Aegilops tauschii pseudomolecules. QTL mapped with SNP markers were more successfully projected (92.2%) than those mapped with SSR markers (66.2%). The QTL were not distributed homogeneously along chromosome arms. Their frequencies increased in the proximal-to-distal direction but declined in the most distal regions and were weakly correlated with recombination rates along the chromosome arms. Databases for projected SSR markers and QTL were constructed and incorporated into the Ae. tauschii JBrowse. To facilitate meta-QTL analysis, eight clusters of QTL were used to estimate standard deviations ([Formula: see text]) of independently mapped QTL projected onto the Ae. tauschii genome sequence. The standard deviations [Formula: see text] were modeled as an exponential decay function of recombination rates along the Ae. tauschii chromosomes. We implemented four hypothesis tests for determining the membership of query QTL. The hypothesis tests and estimation procedure for [Formula: see text] were implemented in a web portal for meta-analysis of projected QTL. Twenty-one QTL for Fusarium head blight resistance mapped on wheat chromosomes 3A, 3B, and 3D were analyzed to illustrate the use of the portal for meta-QTL analyses.

Single layer graphene oxide (SLGO) reinforced titanium (SLGO-Ti) nanocomposites have been achieved by laser sintering. This study focuses on the graphene oxide dispersion and survival in titanium matrix during laser sintering process. Through laser sintering, graphene oxides were dispersed uniformly into titanium matrix to fabricate SLGO-Ti nanocomposites. Microstructures and components of the nanocomposites were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy-dispersive X-Ray spectroscopy (EDS) and Raman spectroscopy. It was confirmed by XRD patterns, EDS maps and Raman spectrum that graphene oxide survived in SLGO-Ti nanocomposites after laser sintering. Nanoindentation measurements showed the laser sintered SLGO-Ti nanocomposites hardness was improved by more than 3-folds than that of pure titanium counterpart.

Thick Fe901 coatings were prepared on Cr12MoV substrates using electromagnetic field (EMF)-assisted multi-layer laser cladding. The effect of the EMF on surface topography, microstructure, multi-layer strategy, phase composition, and wear resistance in the multi-layer laser cladding Fe901 coatings were investigated. The results indicate that the application of EMF decreased the number of defects in coatings produced with laser cladding. Dendrites or cellular crystals oriented perpendicular to the interface were observed in the coatings with and without EMF-assisted growth. The microstructure of the coating formed with the applied EMF gradually transitioned from columnar dendrites to fine dendrites and equiaxed dendrites as the number of cladding layers increased. The coatings with and without an applied EMF primarily contained α-(Fe), α-(Fe,Cr), (Cr,Fe)7C3, CrFeB and FeCrMo phases. The EMF did not affect the phase composition of the coatings, although the intensity of X-ray diffraction peaks from the coating produced in an EMF were changed from those in the coating produced without the field. In addition, the coating produced in the EMF exhibited higher fatigue and abrasion resistance. The coatings prepared in an EMF also displayed narrower, shallower wear tracks, with 78.2% lower mass loss than the conventional coating.

Graphene reinforced titanium (Ti-Gr) nanocomposites have been prepared on AISI 4140 base plate by laser sintering process. The dispersion and survival of graphene in the Ti matrix after laser treatment were discussed. Through laser sintering, graphene sheets were dispersed uniformly into Ti matrix to form Ti-Gr nanocomposites. Microstructures and components of the nanocomposites were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and Raman spectroscopy. It was proved by SEM images, XRD patterns and Raman spectrum that graphene survived in Ti-Gr nanocomposites after laser sintering. Hardness measurements showed the laser sintered Ti-Gr nanocomposites got more than 2-fold higher in Vickers Hardness value than that of laser sintered Ti.