The Heat Treatment Behavior of Super-High Strength Aluminum Alloys by Spray Forming

In order to understand the stress corrosion behavior of super-high strength aluminum alloys by spray forming, different aluminum alloys by different heat treatment was made. The results showed that the alloy with peak aging has the most sensitive stress corrosion cracking, the crack can even be seen using eyes;the alloys with two step aging were better than one step aging alloys, the alloys has not been found stress corrosion cracking.

In-situ Preparation of TiB_2-TiB-Ti Functionally Graded Materials by Improved Sintering Process

An improved multi-step sintering process was used to in-situ prepare TiB2-TiB-Ti FGMs. According to the sintering temperatures, the functionally graded materials （FGMs） were divided into three sections. After sintering at a proper temperature, the three sections were sintered together in turn. The experimental results showed that there were no obvious pores and cracks in the whole TiB2-TiB-Ti FGMs, and no delamination was found in the impacting test with good performance features, which indicated that there were no interface effects in FGMs during penetration, so that the TiB2-TiB-Ti FGMs were an ideal FGM.

Phase and microstructure of CVD alumina-silica coating deposited at relative low temperature

Alumina-silica composite coatings were prepared on the surface of graphite paper by CVD using AlCl3/SiCl4/H2/CO2 as precursor in the temperature range of 300 to 550℃. XRD and SEM were used to examine the phase composition and the microstructure of the coating, respectively. The results indicate that the dense, uniform and adherent alumina-silica composite coating can be prepared on graphite paper substrate by CVD at 550℃ using SiCl4/AlCl3/CO2/H2. The alumina-silica composite coating is composed of a number of spherical particles. Each particle is composed of a number of fine-particle. The phase of the 550℃ composite coating includes γ-alumina containing amorphous silica. The content of Cl element in composite coating decreases with the increase of the deposition temperature. The analysis results of morphology and growth mechanisms of the CVD alumina-silica indicate that the condensation within the boundary layer will be more likely to lead to the formation of gel-particles. The gel-particles size decreases with the increase of deposition temperature in the range of 300550℃. Surface reaction is the main path to generate deposition products at 550℃.

Numerical Simulation and Experimental Research on Penetration of Composite Ceramic Armor by Rod Projectile

The performance of composite ceramic armor penetrated by rod projectile was studied by both numerical simulation and experiment.The penetration and damage mechanisms of the projectile-armor after high-speed collision were also observed by high-speed photography.The experimental results showed that the ballistic performance of composite ceramic armor was highly affected by the density,hardness and toughness of bulletproof ceramic.The flow stress of the failed bulletproof ceramic is not only related to the pressure but also related to the strain rate.The phenomenological method based on Bodner-Partom ceramic model was introduced to derive the growth rate of damage.Numerical simulation results show good agreement with the experimental results.

Microstructure and Mechanical Properties of TiB_2-Al_2O_3 Composites

Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB2-30%Al2O3 can be attained due to the plate-like TiB2 particle and its random orientation and excessive Al2O3 grain growth. When sintering temperature is higher than 1 700 ℃, TiB2 grain growth can be found, which obvious improves flexural strength of TiB2 matrix but decreases toughness. It seems that mechanical properties of TiB2-Al2O3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB2 matrix strength together. Anyway, Al2O3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m1/2 can be achieved inTiB2-30vol% Al2O3.

Effect of ball-milling parameter on mechanical and damping properties of sintered Mg-Zr alloy

Effects of ball-milling parameter on structures and properties of sintered Mg-l.5Zr （mass fraction, %） alloy were researched by metallographic analysis, mechanical properties tests and DMA technology. The results indicate that with 310 r/min rotation speed, the microstructure of the sintered alloy is greatly refined, and Zr-phase distributes uniformly. The micro-hardness, bending strength and damping capacities are the greatest under 310 r/min rotation speed. The damping peak of sintered Mg-l.5Zr alloy increases with increasing frequency under the testing conditions. The relaxation time meets the Arrhenius relationship, and shows the characteristics of relaxation damping.

Study on heat treatment blister of squeeze casting parts

Heat treatment blister is one of the common defects found in squeeze casting parts, which is related to squeeze mode, process and mold. For direct squeeze-casting parts, solution heat treatment can be performed smoothly as long as oil-based paint is not used and air exhaust is well arranged. For indirect squeeze casting parts, solution heat treatment can also be applied when additional factors are taken into consideration, including well designed internal feeding system and strictly controlled liquid metal filling velocity to prevent from inclusions.

Fast Welding of Chromium Carbide and Nickel Alloy by Spark Plasma Sintering

Spark plasma sintering（SPS） was used to weld the ceramics,eg,Cr3C2 and metal,Ni in this paper.It is found that the SPS can weld the Cr3C2 and Ni plates at lower temperatures and shorter holding time comparing with that of hot-pressing（HP）.The binding strength was 113 MPa when the temperature was 1000 ℃ by SPS,compared with 10 MPa by HP at the same temperature.SPS remarkably enhances the atom diffusion in welding.Thermodynamics analysis at different welding temperatures and holding times of SPS or HP shows that the local temperature gradient,different from the past effects of by-passing current,is the dominative mechanism of the SPS welding.