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An as cast high entropy alloy AlCrFeMnNiTi was synthesised to investigate the microstructures and crystal structure. The atomic structure models of this AlCrFeMnNiTi alloy were also built to further investigate the stability and bonding behaviour. It was found that the as cast AlCrFeMnNiTi alloy formed two body centred cubic structures, and typical dendrite and interdendrite microstructures were observed. Two reasonably models based on AlNi and Fe matrix were built to simulate the structures of two phases formed in as cast AlCrFeMnNiTi high entropy alloy. The electron density difference and atomic Mulliken population were also calculated, which revealed the chemical bonding in as cast AlCrFeMnNiTi high entropy alloy. In this study, the probable process of spinodal decomposition in this alloy was also discussed and presented.

According to the experimental dataset on the as cast high entropy alloys with cubic structure, the relationship between the stability and physical parameters of cubic structure has been investigated from the view of the atomic size difference, mixing enthalpy, electronegativity difference and valence electron concentration in the present work to reveal the stability and structure formation in as cast high entropy alloys. The results indicated that the mixing enthalpy is the effective parameter that can predict the stability of solid solutions in as cast high entropy alloys. The atomic size difference, electronegativity difference and valence electron concentration also play important roles in the formation of body centred cubic and face centred cubic crystals. Moreover, the back propagation artificial neural network was established using data collected from the calculated solid solution physical parameters and the structure characteristic of as cast high entropy alloys, and the structure of alloys...

The crystal plasticity finite element method has been adopted to study the plastic deformation behaviour, such as the slip system activation, the number and magnitude of the actived slip system, the rotation character and the macromechanics response of face centred cubic (fcc) single crystal metal during uniaxial tension. Five typical crystalline orientations, including four types of typical fcc texture orientation: Goss orientation, copper orientation, S orientation and brass texture, have been considered, and its effects to plastic deformation have been studied and compared. The results show that the orientation between crystalline and loading direction will influence the slipping character and the macromechanical response: the S crystalline orientation (60, 32 and 65°) has the least number of active slip system (just only 3); the brass texture (35, 45 and 0°) has the smallest magnitude of crystalline lattice rotation; and the brass texture orientation (35, 45 and 0°) has the highest yield stress value.

In order to establish an accurate thermal stress mathematical model of the quenching operation for A357 alloy, isothermal compression tests were performed in the temperature range of 200–500°C and the strain rate range of 0·001–1 s−1 on as quenched A357 (Al–7Si–0·6Mg) alloy. Based on the experimental results, the deformation behaviour of as quenched A357 alloy was investigated in terms of artificial neural network with a back propagation learning algorithm. Using the deformation temperature, strain rate and strain were used as inputs, and flow stress was used as the output in the network. The average absolute relative error between the predicted results that used the back propagation network and the experimental data obtained from compression tests is 2·89%, which indicates that this artificial neural network model is able to predict the flow stress with high precision. Therefore, it can be used as an accurate thermal stress model to solve the problems of quench distortion of parts.

Elevated temperature compressive deformation behaviour of TA15 titanium alloy was investigated at temperatures from 1023 to 1273 K and strain rates from 10−3 to 1 s−1. It was found that the flow stresses of the TA15 alloy dropped with increasing deformation temperature and decreasing strain rate. The microstructure of TA15 alloy was observed and analysed using optical microscope. The volume fraction and the shape of primary alpha phase are influenced by deformation temperature and strain rate.