A.B. Li

Simulation of the large compressive deformation of metal matrix composites with misaligned whiskers

Abstract An embedded cell finite element model is used to analyze the effect of whisker orientation and rotation on the large compressive deformation of aluminum matrix composites reinforced by misaligned SiC whiskers. A large strain non-linear finite element code with updated Lagrangian formulation is used in this simulation. The composite material is regarded as a tilting whisker embedded in matrix and is again surrounded by a sufficient large homogeneous material with the overall mechanical behavior equivalent to the composite. The simulation provides the whisker rotation process and the evolution of stress–strain field during the large compressive loading. The numerical results show that the rotation angle of the whisker increase under the compressive loading, and the tilting whisker rotates toward the more stable position perpendicular to the compressive direction. It is also found that the whisker rotation angle decreases as the initial orientation angle of whisker increases. The effect of the initial whisker orientation is shown to be more sensitive to the stress–strain behavior of whiskers but less sensitive to the matrix during compression. Finally, the averaged stress–strain behavior of the composite material is quite sensitive to the initial orientation of whiskers.

Titanium Aluminum Alloy Fabricated by Pressure Infiltration and Heat Treatment

Titanium Aluminum alloy is one of the most promising high temperature materials due to its excellent high temperature properties such as anti-creep, antioxidant, high stiffness, and high yield strength. However, titanium aluminum alloy application is limited because of its bad plasticity and difficulty in forming. In the present research, a novel method, which is the combination of pressure infiltration and heat treatment, was used to produce titanium aluminum alloy. Using the OM, SEM, XRD and EDS, the pressure infiltration and heat treatment were investigated, and then the effects of two processes on density and hardness were analyzed. In our work, the optimized parameters of the TiAl Alloy preparation were: Al-Si eutectic alloy pressure infiltration into Ti powders at 600°C, and one-step heat treatment at 1200 °C.

Microstructure and Reaction Mechanism of Multi-Laminated Ti-(SiCp/Al) Composites Subjected to Annealing at 1300°C

The multi-laminated Ti-(SiCp/Al) composite was produced by hot press and subsequent hot roll bonding of Ti and SiCp/Al foils. The microstructure evolution of the composite in reaction annealing was investigated by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDX) and X-ray diffractometer (XRD). The results show that after the reaction annealing at 1300°C for 3h, the Ti and SiCp/Al foils were completely consumed and transformed into the TiAl composite with a microlaminated structure. The microlaminated microstructure of the composite is composed of Ti3Al/(TiAl+Ti5Si3p)/Ti5Si3/duplex-phase (TiC+Ti3AlC) layers. The reaction mechanism is elucidated by employing the reaction model.

Effect of hot extrusion and heat treatment on CNTs–Al interfacial bond strength in hybrid aluminium composites

Moderate carbon nanotubes (CNTs–Al) bond strength plays a key role in determining the mechanical and physical properties of the composite. Here, the effect of hot extrusion and heat treatment on the CNTs–Al reaction and their bond state were investigated in SiCw + CNTs/6061Al hybrid composites prepared by squeeze casting. The results show that the reaction activation energy between CNTs and molten 6061Al is slightly higher than that between CNTs and 2024Al. Reaction between CNTs and Al may also happen at temperature below solidus temperature of 6061Al. After the hot-extruded composite was heat-treated at 580 °C for 1 h, the composite shows enhanced tensile strength due to the improvement of interfacial bond strength between CNTs and Al. Fracture surface observation reveals that the improvement of the tensile strength is related to the enhancement of CNTs–Al bond strength. This demonstrates that controllable interfacial reaction may be adopted to introduce moderate interaction layer between CNTs and Al, and thus raise their bond strength.