Aluminium versus steel in the family car — the formability factor

Abstract

Mechanical properties which influence the competition between high-strength low-alloy steels and aluminium alloys, for use in load-bearing body components of light-weight passenger vehicles, are identified. Detailed consideration is given to effects of chemical composition, microstructure and mechanical strength on the forming limits attained in conventional room-temperature stretch-forming operations. It is shown that understanding of the structure-sensitive mechanisms which influence the development of strain-localisation in stretching is providing useful guidance in the selection and development of formable sheet alloys with moderately high strengths. Some advantages which wider exploitation of warm sheet-forming techniques could offer — particularly in applications to higher-strength alloys — are described. Emphasis is given to the possibility of making outstanding advances in the scope and versatility of sheet-forming by developing applications of temperature gradients in the control of the distribution of flow-strengths during forming. It is concluded that aluminium alloys will lend themselves more easily to practical applications of such warm sheet-forming techniques.