Abstract
There are various kinds of smart materials with a martensitic transformation, such as the shape memory alloy and the tranformation-induced plasticity (TRIP) steel, etc.; their applications to actuators, structural materials, etc., are investigated. The martensitic particles orient against the loading axis in the micro region so that it may be possible to improve their mechanical properties by the control of their orientation like the composite materials. Here, the fraction tensor, which components are the line fractions of the martensite, was defined in order to evaluate the orientation of the martensite. The validity of the the fraction tensor for investigating their orientations is discussed by a comparison of the fabric tensor. Then, the fraction tensors were measured from the micrographs of TRIP steel previously obtained. Furthermore, the orientation of the martensite in the TRIP steel was discussed by a polar diagram of the line fraction and the fraction tensor. Finally, the dependence of the fraction tensor on plastic strain, temperature and stress state was discussed.
