传统材料在国民经济中的地位与可持续发展(2) S.J.T.U. Phase Transformation and Applications cn 汽车用钢，特别是多相钢 40- TRIP steels M.Militger,Science,2002. 298:975. 30- DP steels Martensitic 20 steels Conventional steels The weight fraction of steel 300 500700900110013001500 and iron in an average family Tensile strength(MPa) car has decreased from 74% in 1978 to 67%in 1997.Yet Ductility-strength relationship of steels.As tensile strength increases,corventional steels over the same time period, show a decrease in elongation to failure,which is a measure of formability;that is,the higher its that of high-strength steels strength,the less formable is the steeL Dual- has risen from 4%to 9% phase(DP)and TRIP steels deviate from this gen- eral rule by combining high strength with signifi- cantly higher elongation values than those of conventional steels of the same strength leveL SJTU Thermodynamics of MaterialsPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2006 © X. J. Jin Introduction 传统材料在国民经济中的地位与可持续发展（2） M. Militger, Science, 2002, 298: 975. 汽车用钢，特别是多相钢 The weight fraction of steel and iron in an average family car has decreased from 74% in 1978 to 67% in 1997. Yet over the same time period, that of high-strength steels has risen from 4% to 9%