Effects of Melt Vibration During Solidification on the Mechanical Property of Mg-Al-Zn Alloy

Abstract The effect of mechanical mould vibration during melt solidification on the mechanical properties of an AZ91 magnesium alloy was investigated. This was tested in the frequency range from 0 to 24 Hz and at two vibration intensities; 5V-peak to peak and 10V-peak to peak. Mechanical tests such as tensile test, hardness test and impact test were carried out on the samples. Improvements were observed in the mechanical tests within the frequency threshold of 12 and 16 Hz. It was concluded that vibration of moulds during melt solidification have some refining effects on the grain structures of the alloy and improve the mechanical properties of the sample. The optimum frequency of mold vibration is between 12 and 16 Hz

MECHANICAL PROPERTIES AND PHASE EVOLUTIONS IN HEAT-TREATED CAST Al-SiC-TiO2 METAL MATRIX COMPOSITES

The effect of heat treatment with an addition of titania on the phase development and mechanical properties of sand casted Al-SiC-TiO2 metal matrix composite was investigated. The standard samples dimensions for tensile properties, wear and hardness were prepared. These samples were heat treated at different temperature of 180°C to 220°C without solution treatment. The samples were held at the heat treatment temperature for an hour after which they were allowed to cool in the air. Thereafter, samples were subjected to various mechanical and wear tests, respectively. The phases evolved due to heat treatment of the samples were examined using X-ray diffractometry. It was observed that the increase in heat treatment temperature of samples leads to the formation of precipitates within the aluminium matrix composite reinforced with SiC. The addition of 5 % titania inhibits the formation of aluminium silicon carbide phases in preference to SiO2 and TiO2 . The increase in heat treatment temperature leads to the formation of precipitates like TiSi2 , Si11.4TiO24.4, TiC, Al2 O3 and buckminsterfullerene C70 within the aluminium matrix composite. The addition of 10 % titania leads to the development of precipitates like Al5 Ti3 and Ti-rich oxides with the aluminium matrix. At 220°C, alumina was formed within the metal aluminium matrix and no trace of SiC was found. All the samples have low wear loss but the heat treated at 180°C sample (A) has the lowest wear loss. The heat treatment of the sample without solution treatment has impact on the phase development in the samples. It gives rise to the development of precipitates in the samples which affects the hardness and other mechanical properties. The addition of SiC and TiO2 to aluminium matrix makes the sample harden. Sample A heat treated at 200°C have the highest hardness

Laser Based Additive Manufacturing Technology for Fabrication of Titanium Aluminide-Based Composites in Aerospace Component Applications

Titanium aluminides has the potential of replacing nickel-based superalloys in the aerospace industries because its density is almost half that of nickel-based alloys. Nevertheless, the room temperature properties (ductility) have made the wider application of this class of intermetallic alloy far from being realized. This has led to various research been carried out in adjusting the production processing and/or material through alloying, heat treatment, ingot metallurgy, powder metallurgy and most recently additive manufacturing processing. One of the additive manufacturing processing of titanium aluminide is laser engineered net shaping (LENS). It is used to produce components from powders by melting and forming on a substrate based on a computer-aided design (CAD) to shape the components. This contribution will focus on the laser processing of titanium aluminides components for aerospace applications. Also, the challenges confronting this processing techniques as well as suggested finding to solve the problems would be outlined. The objective of this work is to present an insight into how titanium aluminides components have been developed by researchers with emphasis on aerospace applications