Materials Science Forum Vol. 750

Abstract: Multiple target magnetron sputtering technique was employed for the deposition of (Cr,V)2AlC thin films, on the substrate of Si wafer at temperatures ranging from ambient to 840 K. The chemical composition and crystal structure of the deposited thin films were analyzed, surfaces as well the cross sections observed. The experimental results demonstrated that the temperature of the substrate does not affect the chemical composition of the deposited thin films. Deposition at room temperature or moderate elevated temperatures was found to result in amorphous films, whereas crystalline MAX phase thin films were obtained at high temperature. The transition of the substrate temperature was found to be around 743 K. The thin films deposited at temperatures below the transition showed the featureless flat surfaces. At high substrate temperatures, crystalline MAX thin films were formed. When deposited at temperatures near the transition, amorphous/nanocrystalline double layer thin films were deposited.

Abstract: Abstract: With the industrial development and improvement of mechanical product quality, the demand of part surface quality and accuracy gets more and more high. As some parts of complex shape, can’t be machined by the traditional processing technology, therefore, the magnetic abrasive technique was proposed. The magnetic abrasive particles play an important role in the magnetic abrasive finishing, it use strong magnetic iron particles and abrasive particles mixed together (called magnetic abrasive). The prepared method of magnetic abrasive one of is sintering method, the aim is to change the internal structure of abrasive particles, make the abrasive particles is distributed on the surface of magnetic iron particles, get a kind of magnetic abrasive, which can be magnetized in a magnetic field and improve processing efficiency and surface quality in magnetic abrasive finishing. In this paper, sintering method is used to make iron particles, abrasive particles mixed with some binder, after suppression, drying, sintering, cooling, break up and sieving, analysis surface morphology and composition of the magnetic abrasive particles by scanning electron microscopy, discusses the effect of the abrasive particles size ratio, sintering time, sintering temperature for the finishing performs, the preparation process of the magnetic abrasive has been optimized, work out the standard of preparation of the magnetic abrasive process

Abstract: Nylon 6 clay hybrid (NCH) composite consists of nano-sized Montmorillonite and nylon 6 matrix. The testing materials were nylon 6, NCH-2 (2 wt% clay reinforced composite) and NCH-5 (5 wt% clay reinforced composite). Fatigue tests at the glass transition temperatures (35 °C and 50 °C) were performed with a stress ratio of 0.1 and frequency of 0.1Hz. NCH-2 had the highest fatigue strength at room temperature, but NCH-5 had the highest fatigue strengths at 35 °C and 50 °C. It was found that the fracture origin changed from surfaces to interior of specimens with an increase in temperature in NCH-2 and NCH-5.

Abstract: SiC whisker reinforced Si3N4 composite was used for studying crack healing behavior. Surface crack and straight-through crack were introduced on the tensile surface of specimens by Vickers hardness indenter and single edge pre-crack beam method. The cracked specimens were heat-treated at 1000 , 1100 , 1200 and 1300 for 1 hour in air. Bending strength was measured at room temperature by three point bending tests system. It was investigated that the best heat treatment temperature of Si3N4/SiC whisker composite is 1200 -1300 . The relationship between bending strength and logarithm of crack area was near linear and parabola in original and heat-treated specimens, respectively. Crack healing behavior was analyzed by oxidation filling model according to oxidation kinetics.

Abstract: Compressive tests of Zr6Ni3AlX（X=1 to 3），Zr7Ni3AlX（X=1 to 3），Zr8Ni3AlX（X=1 to 3），Zr9Ni3AlX（X=1 to 3），Zr3Ni4AlX（X=1 to 3）and Zr10Ni3AlX（X=1 to 3）bluk metallic glass（BMG） were carried out to investigate the compositional dependence of mechanical properties． The strength increased but the ductility decreased with an increase in Al content．Moreover，it was confirmed that the formation of multiple shear bands became difficult with an increase in glass forming ability．

Abstract: In this research, the effect of Ta addition on the formation, thermal stability and corrosion behavior of Ti-Zr-Cu-Pd bulk metallic glasses were investigated. The results revealed with minor addition of Ta, higher corrosion resistance and compressive strength as well as large plastic deformation were achieved. Minor addition Ta is effective for the formation of more protectively passive film during the process of anodic polarization. In addition, proper volume fraction nanoparticle with small size is responsible for the large plastic deformation of the as-cast Ti-based bulk metallic glasses with 1% Ta addition.

Abstract: The purpose of this study was to understand the effects of thermal exposure temperature on residual stress in thermal grown oxide (TGO) on NiCrAlY coating. The residual stresses in the TGO layer were measured by photo-stimulated luminescence spectrum. High velocity oxygen fuel sprayed (HVOF) method was used to fabricate NiCrAlY coating material. The thermal exposure tests were conducted in air at 900°C, 1000°C, 1100°C for up to 1000 hours using an electric furnace. It was shown that the thickness of the TGO increases with an increase in thermal exposure time with a parabolic curve. The residual stress in the TGO layer increases in thermal exposure time up to 75 hours, and then, the residual stress in the TGO layer decreases slowly. The effects of surface roughness on the residual stress in the TGO were discussed based on experimental results and analysis.

Abstract: The Ni-P-Al₂O₃ composite film was coated on mild steel of SS400 with electroless plating method. In this process, different sizes of Al₂O₃ particles and different blended amounts of Al₂O₃ particles into the plating solution were applied. From the surface and cross section observation, it is known that the Al₂O₃ particles were uniformly dispersed in the Ni-P alloy. The highest corrosion resistance and the highest wear resistance of the Ni-P-Al2O3 composite film were obtained when adding Al2O3 particles with the mean diameter of 0.05μm into the plating solution at the blended amount of 1.0g/L.

Abstract: The effects of small amounts of Si on the glass-forming ability, thermal stability and mechanical property of a TiZrCuPdSn bulk metallic glass were investigated. The addition of Si caused the decrease of glass-forming ability and the increase of the supercooled liquid (SCL) region. With 2 at.% Si addition, a significant SCL region of 80 K was obtained, which indicated high thermal stability of the glassy alloy and was in favor of secondary working by viscous flow deformation. With increasing Si content, the plasticity decreased.