Structure and magnetostriction of Tb_(0.4)Nd_(0.6)(Fe_(0.8)Co_(0.2))_(1.90) alloy prepared by solid-state synthesis

Mechanical alloying (MA) and subsequent solid sintering process was used to prepare the Nd-containing magnetostrictive Tb0.4Nd0.6(Fe0.8Co0.2)1.90 alloy. The structure, thermal stability and phase transformation were investigated as functions of composition, milling process and annealing temperature. An amorphous phase was formed by high-energy ball milling for 5 h with the ball-to-powder weight ratio of 20:1, which crystallized into MgCu2-type and PuNi3-type crystalline structure with different annealing temperatures. The magnetoelastic properties were investigated by means of a standard strain technique. The high Nd-content (Tb,Nd)(Fe,Co)2 Laves phase for the composition Tb0.4Nd0.6(Fe0.8Co0.2)1.90 was synthesized by MA process plus annealing at 500 ℃ for 30 min.

Effects of high temperature annealing on the dislocation density and electrical properties of upgraded metallurgical grade multicrystalline silicon

High temperature annealing was performed on upgraded metallurgical grade multicrystalline silicon (UMG multi-Si) wafers with a purity of 99.999%. The samples were mechanically polished and chemically etched, and then the microstructures were observed by a scanning electron microscope (SEM). The minority carrier lifetime and resistivity of the samples were measured using microwave photoconductance decay and four-point probe techniques, respectively. The results show that the electrical properties of the samples decrease rather than increase as the annealing temperature increases, while the number of dislocations in bulk Si reduced or even disappeared after annealing for 6 hours at 1100–1400°C. It is considered that the structural microdefects induced by the high concentration of metal impurities (including interstitial or substitutional impurities and nanoscale precipitates) determine the minority carrier recombination activity and thus the electrical properties of UMG multi-Si wafers rather than dislocations in bulk Si.

Effect of AlN Thickness on Structure and Properties of AlN/Al Dual Protective Coatings on NdFeB by DC Magnetron Sputtering

In order to improve the corrosion resistance of NdFeB,AlN/Al dual protective coatings were prepared by DC magnetron sputtering in a home-made industrial apparatus.The inner Al layer with an excellent toughness was deposited onto NdFeB substrate firstly.And then the outmost AlN layer with a higher hardness was prepared with the nitrogen/argon mixture gas of the nitrogen partial pressure at 50%of the total pressure of 0.5 Pa and depositing time of 30,50 and 70 min,respectively.The denser outmost AlN layer was formed on the inner Al crystal layer.There is an occurrence of the interfacial reaction and metallurgy bonding in the interface layer between the coatings and NdFeB substrate.It has been found that the thickness of outmost AlN layer has a significant impact on corrosion resistance.For 50 min to deposit outmost AlN layer,AlN/Al coated NdFeB has the best corrosion resistance.

Quantitative microstructure and fatigue life of B319 casting alloys

In this study, the microstructure of B319 casting alloys and effects of five different casting conditions on microstructure were studied. Multi-scale microstructure was quantified in terms of secondary dendrite arm spacing （SDAS）, and Si particle size and aspect ratio. The effects of SDAS, Si aspect ratio and size on fatigue life were analyzed. The results indicate that the size and aspect ratio of Si particles are a function of SDAS which is dependent on cooling rate during solidification. The fatigue life decreases with SDAS increasing as SDAS is smaller than 30 pm while it increases with SDAS increasing as SDAS is larger than 60 ~tm. In addition, the fatigue life decreases with Si aspect ratio and size increasing at the same SDAS. Moreover, SDAS and Si particles have also influence on fatigue fracture, such as the area of cracks propagation region and the roughness of fatigue fracture. The cracks propagation area is smaller, and the fatigue fracture is similar to tensile fracture with larger SDAS. Besides, the longitudinal section of fatigue fracture is rougher with large SDAS and elongated Si particles.

Mechanical Properties of TiN Coating on Nanocrystalline Surface Layer of 304 Stainless Steel

Surface nanocrystallization(SNC)can markedly improve surface mechanical properties of metallic materials and accelerate thermal diffusion of elemental atoms.In this work we study the effects of SNC on structure and mechanical properties of TiN coating on 304 stainless steel substrate.The steel was subjected to 15 min surface mechanical attrition treatment(SMAT)to obtain a nanocrystalline surface layer with thickness about 30μm.TiN coating was deposited on the surface nanocrystallized and the coarse-grained steel substrates by multi-arc ion plating.X-ray diffraction shows that TiN(111)orientation of the coating is much reduced due to SNC treatment.Mechanical tests show that the nanocrystalline surface layer has obviously increased surface hardness of the coating system;toughness and adhesion of the coating,impact resistance of the coating system are also improved.Advantages of SNC-hard coating processing over the conventional duplex treatment consisting of thermal diffusion process-hard coating are shortly discussed.