Mr Haoxiang Gao
Research Area
Superplastic forming (SPF) and Solution heat treatment, cold in die forming technology (HFQ) on Al-Li alloy
Aluminium Lithium (Al-Li) alloy has become increasingly popular material used in the aerospace industry. Li has extremely low density, for each 1wt% addition, the density of the aluminium alloy could be reduced by 3wt%, thus Al-Li alloy could lead to significant weight reduction in the aero-structural components. In order to form complex-shaped Al-Li components, Superplastic Forming (SPF) technology and HFQ technology ( i.e. the Solution Heat Treatment) are employed. Until now, SPF technology has been developed for more than 40 years and already become reality with large scale of metallic sheet materials being superplastically formed. As a new technology, the HFQ is a novel hot forming technology which combines forming and heat treatment in one operation.
The mechanical properties of Al-Li alloys at superplastic forming and HFQ forming conditions including their flow stresses, ductility and formability are very important for the FE simulation of the forming process. Since the superplasticity is achieved via the grain rotation and grain boundary sliding at elevated temperatures (normally greater than 450 °C), the ultra-fine grain size (approximately < 20µm), and the fine dispersion of thermally stable particles which pin the grain boundaries and a fine structure at the forming temperature require particular attention. The HFQ technology has been used for forming many medium and high strength aluminium alloys, such as AA6XXX and AA7XXX, as an effective manufacturing technique. However, the HFQ forming of Al-Li alloys requires a great amount of investigations in order to benefit from these optimal material properties, for instance, the effect of Solution Heat Treatment on strengthening mechanism and the corresponding mechanical properties obtained on Al-Li alloy are interestingly concerned by HFQ.
In both forming techniques, the prediction of flow stresses, formability and microstructure evolution etc. of Al-Li alloys during the forming process are considered as the main scientific challenges. In addition, the comparisons between HFQ and SPF technologies are required by considering the formability and thickness distribution of the final products and also the difference of microstructural mechanism during the forming process.
Research Keywords
- Aerospace industry
- Aluminium lithium alloy
- Solution heat treatment
- Formability
- Superplasticity
- Microstructural Mechanism
Qualifications
- MEng in Aerospace materials