Through Process Prevention of Recrystallization in Hot Formed Aluminium Structural Car Components
Aluminium is increasingly used in structural components in cars. The advantages are many, and recyclability, weight saving and energy absorption during impact and are often considered as the most important. There are also several disadvantages compared to iron and steel, i.e. material cost, low stiffness, lack of fatigue limit, high thermal conductivity, high thermal expansion coefficient, corrosion susceptibility and others. To enhance the advantages and to minimize the disadvantages, several actions can be made. To prevent recrystallization is one of them, and has to be dealt with from the melt through all thermo-mechanical, mass reducing and assembly processes – “from the ore to the car”. As recrystallization may reduce the static strength and fatigue life time in a finished component considerably, preventing recrystallization is as important as to optimize component geometry. Additionally, there is considerable risk of inter-granular cracking or melting during thermo-mechanical processing, especially those involving very high strain and forming temperatures above eutectics. To prevent recrystallization, a well balanced budget on chemical composition, strain, strain rates and temperatures is essential. Examples of successes and failures are vital ingredients of the base of knowledge in development of highly utilized aluminium car components. All process steps, from alloying and melt treatment of wrought aluminium alloys to the assembly of a finished component, can influence on product performance. AlMgSi1 alloys are used as examples in evaluating recrystallization in this paper. By focusing on recrystallization, other major factors influencing performance are not neglected, but not further discussed here.
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
J. Sandvik et al., "Through Process Prevention of Recrystallization in Hot Formed Aluminium Structural Car Components", Materials Science Forum, Vols. 638-642, pp. 315-320, 2010