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A single-layer of three-pass overlapped Al-Mg-Mn-Sc-Zr alloy was successfully fabricated by additive friction stir deposition (AFSD). Microstructures of the deposit were analyzed using optical microscope, scanning electron microscope and electron backscatter diffraction. Vickers hardness was evaluated over the whole cross-section of the deposit. Tensile tests were performed on the deposit as well as the base material using digital image correlation technique. The results indicated that dynamic recrystallisation occurred in the deposit, producing fine and equiaxed grains whose average grain sizes in overlapped zones were reduced to approximately 2–5 μm. The high-angle grain boundaries in the upper regions of the first-third and the first-second passes overlapped zones are 85% and 76%, respectively. The hardness distribution is non-uniform throughout the cross-section of the deposit, with minimum hardness of about 90% of the BM on the retreating side of the second pass and the two overlapped zones. The ultimate tensile strengths of specimens on the first-third and the first-second passes overlapped zones are 343 MPa and 308 MPa. The elongation of the specimens on the first-third passes overlapped zone is 22.2%, higher than that of the base material (19.5%), while the elongation of the specimens on the first-second passes overlapped zone drops to 10.4%. [ABSTRACT FROM AUTHOR]

In order to improve the ZrC-SiC ceramic and TC4 brazed joint property, graded double-layered SiC particles (SiCp)-reinforced TC4-based composite structure (named as GLS for convenience) was designed to relieve the residual stress in the joint. The GLS was successfully fabricated on TC4 substrate by double-layered laser deposition technology before the brazing process. The investigation of the GLS shows that the volume fraction of SiCp in the two composite layers was graded (20 and 39 vol pct, respectively). Ti5Si3 and TiC phases formed in the GLS due to the reaction of SiCp and TC4. The laser power-II (the laser power for the second deposition layer) affected the microstructure of the GLS significantly. Increasing the laser power-II would promote the reaction between the SiCp and TC4. But the high laser power-II made the layer I remelt completely and the two layers became homogeneous rather than graded structure. In the ZrC-SiC and TC4 brazed joint, the CTE (coefficient of thermal expansion) was graded from the TC4 to the ZrC-SiC due to the GLS, and the strength of the joint with the GLS (91 MPa) was higher than that without the GLS (43 MPa). [ABSTRACT FROM AUTHOR]

The effects of electropulsing on the machinability and microstructure of the machined surface of GH4169 superalloy are investigated in the present work. The results indicate that the machinability and the surface quality of GH4169 superalloy achieve evident improvements during the electropulsing-assisted turning process (EP-TP) at appropriate electropulsing parameters compared with the traditional dry turning process (TD-TP). In EP-TP at the frequency of 400 Hz and the root-mean-square (RMS) current density of 0.64 A mm-2, the main cutting force, the axial surface roughness, and the surface microhardness are reduced dramatically. In addition, the quality of machined surface and the ability of plastic deformation are also facilitated significantly under the effects of electropulsing. For GH4169 superalloy, the enhanced ability of the plastic deformation and the promoted mobility of dislocations in the cutting layer under the influence of the coupling of thermal and athermal effects of the exerted electropulsing are likely the primary reasons for the observed phenomena. [ABSTRACT FROM AUTHOR]

The effect of extrusion combined with shear (ES) on the microstructure and mechanical properties of magnesium alloy AZ31 is studied. The additional die providing shear deformation of the extruded bars (two successive turns of the calibrating channel to equal opposite angles) provides refinement of grains. Growth of the deformation temperature causes grain growth. The intensity of the x-ray reflection from basal plane (0002) after the ES increases. After the deformation at 420°C fracture mainly develops by the transgrain mechanism. After the deformation at 450°C the maximum hardness corresponds to the largest grain size in the central part of the bar, and the fracture is chiefly determined by twinning. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1007/s00339-016-0605-7. 3X-ray diffraction patterns of AZ61 fabricated by ES process with different die channel angles The authors would like to apologise for any inconvenience caused. [Extracted from the article]

The transient liquid phase diffusion bonding (TLPB) method was used to repair an artificial crack in Inconel 738, which was notched by a femtosecond laser. Mixed ratios of BNi-1a:DF-4B were investigated at the bonding temperature of 1373 K (1100 °C) for 2 to 36 hours. The effect of borides on the mechanical properties of TLPB repaired joints was studied through analysis of the microstructure, fracture path, and morphology observations. The borides formation, morphology, distribution, and joints strength were studied in detail. The results showed that the diffusion of B can either increase or decrease the joint strength, depending on its distribution and morphology. The amount of large blocky Ni-B compounds in the precipitate zone were reduced with increasing holding time, which resulted in an increase in joint strength. Nevertheless, further increasing the holding time led to a decrease in joint strength because of the formation of continuous acicular borides in the diffusion-affected zone. The fracture modes of TLPB joints were also discussed on the basis of the microstructure and fractography. [ABSTRACT FROM AUTHOR]

In many industrial applications, large-sized SiC components are increasingly desired through a conventional and pressureless brazing method. In present study, Ni-Si-Ti powder mixtures containing 0~10 wt.% Ti were used to braze SiC ceramics. Differential thermal analysis (DTA) and wetting tests were carried out to determine the appropriate joining temperature to be at 1450 °C. Microstructure, phase constituents, and mechanical strength of the prepared SiC joints were characterized. For a brazing composition without Ti addition, the interlayer primarily consists of NiSi and Ni3Si2 phases. With the addition of Ti, Ni49Ti14Si37 phase is newly formed within the interlayer besides the Ni-Si compounds. The bending strengths of SiC joints locate in 66~75 MPa as brazed at present conditions and the specimens generally fracture from the interface between alloy interlayer and SiC substrate. [ABSTRACT FROM AUTHOR]

The Fe-Si-Al soft magnetic powder cores with five particle size distributions were prepared. The microstructure study revealed that the cores had a fairly compacted structure with a uniform insulation layer of the phosphate forming on the surface of the magnetic particles. The particle size distribution was found to have the great influence on the core's magnetic properties. The increase of the percentage of the small particles results in the decrease of the effective permeability, the improvement of the DC-bias performance, and the deterioration of the core loss. The effects of the distributed air gap and the demagnetization field on the core's magnetizing process were believed to be the underlying physical origins. The core losses at the frequencies lower and higher than 150 kHz were found to be mainly determined by the hysteresis loss and the eddy-current loss, respectively. The good magnetic performances of the Fe-Si-Al powder cores with the effective permeability of about 55-60 were finally achieved as follows: the percent permeability at 100 Oe is up to 52.3 %, and the lowest core loss at 50 kHz/1000 Gs is 270 mW cm. [ABSTRACT FROM AUTHOR]

The AlFeCoNiCrSn high-entropy alloys (HEAs) are fabricated. The microstructure and mechanical properties of the alloys are investigated. The results show that alloying elemental content plays a significant role in the microstructure and properties of the alloys. When Sn content is <0.05, the AlFeCoNiCrSn HEAs consist of only BCC solid solution and possess high strength and good plasticity. While Sn content is above 0.05, the CoSn intermetallic compounds form, formation of intermetallic compounds decreases the plasticity of alloy. The maximum strength and stain values of alloys can reach 2,180 MPa and 18.1%, respectively. [ABSTRACT FROM AUTHOR]

A log-pile photonic crystal of CdS nanoparticles–polymer nanocomposites was successfully fabricated by a novel method combining the two-photon polymerization technique and in situ synthesis of CdS nanoparticles in a polymer matrix. The photonic band gap of the three-dimensional (3D) log-pile photonic crystal is confirmed and becomes more effective for CdS nanoparticles–polymer nanocomposites than polymer doped with Cd2+ ions, because the nanocomposites possess a higher refractive index than the polymer. The proposed concept in the new fabrication method for a 3D microstructure of polymer nanocomposites should be of critical importance in providing a general methodology for functionalization of materials via functional nanocomposites used in the field of laser microstructure fabrication. [ABSTRACT FROM AUTHOR]