HFQ and SPF Forming on Al-Li Alloy Components
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 Al-Li alloy can be reduced by 3%, thus Al-Li alloy could lead to significant weight reduction in the components.
In order to form complex-shaped Al-Li components for aeronautic applications, Superplastic Forming (SPF) technology is usually used, which requires the simultaneous control of many critical parameters including: temperature, strain rate via applied gas pressure and blank holding force etc. Thus, SPF is a sophisticated process which enables the forming of complex shaped components by using relatively inexpensive tooling; especially it is highly suitable for low volume production of complex shaped components. However, there are a number of drawbacks in the superplastic forming technology. 1) SPF requires long processing time which takes several minutes, sometimes up to 2 hours for critical parts. 2) Localised thinning of SPF product is one of major problem 3) a limited number of materials are capable by using SPF technology.
An alternative technology to form high-strength complex-shaped Al-Li components could be the (Solution Heat Treatment, Forming and in-die Quenching) HFQ process, which is a novel hot forming technology combining forming and heat treatment in one operation. In the past years, the HFQ technology has been used to form a number of medium and high strength aluminium alloys, such as AA5XXX, AA6XXX, AA2XXX and AA7XXX. However, the feasibility of HFQ forming of Al-Li alloys needs to be studied.
Mr Haoxiang Gao (Imperial College London)