Elimination of Shrinkage Cavities by Liquid Hot Isostatic Pressing in Aluminum Alloys under Superplastic Conditions

The liquid hot isostatic pressure in superplastic conditions was applied to eliminate macroporosity in a die cast Al-12%Si eutectic alloy. The removing of macroporosity provides the yield stress increase of 56%, the ultimate tensile strength increase of 46%, the total elongation increase of 21%, the fracture toughness increase of 340% and the fatigue strength increase of 58%. Remarkable improvement of mechanical properties is caused by suppression of crack initiation on internal coarse pores.

Fabrication and Characterization of SiC-Coated Multi-Walled Carbon Nanotubes Reinforced Reaction Bonded SiC Composite

SiC-coated multi-walled carbon nanotubes (SiC-coated MWNTs) made by RF magnetron sputtering were introduced into the SiC suspensions to enhance the mechanical behaviors of reaction bonded silicon carbide ceramics. The composites were prepared by the epoxy resin curing and liquid silicon infiltration at 1550°Cfor 60min. The distribution, morphology, and reinforcing behaviors of MWNTs were investigated. X-ray diffraction (XRD) reveals that the MWNTs were reserved during the reaction sintering. The flexural strength and fracture toughness increase with MWNTs ranging from 0wt% to 0.5wt%, reaching the peaks value of 347MPa and 4.3MPam1/2 respectively at the MWNTs fraction of 0.5 wt%. This improvement derives from the MWNTs pullout. The consequent decline at MWNTs fraction of 1wt% is resulted from the corrosion of agglomerated MWNTs and the increase of residual silicon.

Effects of RbI on the Optical and Mechanical Properties of Ge23Se67Sb10 Glass

(100-x)Ge23Se67Sb10-xRbI glasses were prepared by the melting technique. The structures and properties were investigated by using SEM, XRD, DSC, FTIR and Vickers hardness tester. It is found that, with increasingx, the glass-forming ability and the infrared transmittance of (100-x)Ge23Se67Sb10-xRbI samples decrease, the thermal stability and the fracture toughness increase, the Vickers hardness increases first and then decreases. When the content of RbI is 1%, the hardness reaches the maximum value 1985 MPa, at this point, the fracture toughness reaches 10.41 MPamm1/2.