Volume Fraction Dependent Wear Behavior of Titanium-Reinforced Aluminum Matrix Composites Manufactured by Melt Infiltration Casting

This study aims to investigate the effect of volume fraction of commercially pure titanium (CP-Ti) on microstructural, mechanical, and tribological features of A356 aluminum matrix composites. Vacuum-assisted melt infiltration casting was performed to produce composites with 50%, 65%, 75%, and 80% CP-Ti contents. CP-Ti sawdusts were assembled under mechanical pressure in order to attain porous one-piece CP-Ti preforms which were infiltrated by A356 melt at 730 °C under 10−5 Pa vacuum atmosphere. TiAl3 layer was formed at the interface between A356 and CP-Ti phases. Owing to increased diffusion time through decreased diffusion path length, both thickness and hardness of TiAl3 phase were increased with increasing CP-Ti ratio, whereas the best wear resistance was obtained at 65% CP-Ti ratio. The main reason for decrease in wear resistance of 75% and 80% CP-Ti reinforced composites was fragmentation of TiAl3 layer during wear process due to its excessively increased brittleness. Strongly bonded TiAl3 phase at the interface provided better wear resistance, while weakly bonded ones caused to multiply wear rate.

Web Reinforced AZ91 Composites with Enhanced Strength and Plasticity

Stainless steel web reinforced AZ91 alloy were fabricated by melt infiltration casting method. The mechanical properties of the resultant composites were much improved in regarding to the elastic modulus, 0.2% offset yield strength, ultimate compressive strength and the strains compared to the unreinforced counterpart. The interaction between the web and the dislocations in the matrix and the load transfer from the matrix to the reinforcement are the strengthening factors. While the wire being broken, bended and pulled out of the matrix, especially the activation of much more slip bands in the matrix, suggest that both the load transfer mechanism and the dislocations proliferation mechanism contribute to the plasticity of the composites.

Melt infiltration casting of bulk metallic-glass matrix composites

The authors describe a technique for melt infiltration casting of composites with a metallic-glass matrix. We made rods 5 cm in length and 7 mm in diameter. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed composites were those reinforced with tungsten and carbon steel continuous wire reinforcement. The Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 matrix was quenched to a glass after infiltrating the reinforcement. We analyzed the microstructure of the composites by x-ray diffraction and scanning electron microscopy. The measured porosity was less than 3% and the matrix was about 97% amorphous material.