High strength steels S.J.T.U. Phase Transformation and Applications The weight fraction of 50- steel and iron in an average family car has 40 TRIP steels decreased from 74% in 1978 to 67%in 1997.Yet over the 30- DP steels same time period,that Martensitic of high-strength steels 20- steels has risen from 4%to Conventional 9% steels 10- 300 500700 900110013001500 Tensile strength(MPa) M.Militger,Science,2002,298:975 SJTU Thermodynamics of Materials Spring 2010 X.J.Jin Introduction 19/65Phase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2010 © X. J. Jin Introduction 19/65 M. Militger, Science, 2002, 298: 975. 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% High strength steels