Master of Engineering (Hons.)
Department of Materials Engineering
Liu, He, Influence of carbon on martensitic transformation and shape memory effect of Fe-Mn-Si alloys, Master of Engineering (Hons.) thesis, Department of Materials Engineering, University of Wollongong, 1996. http://ro.uow.edu.au/theses/2489
This thesis reports the influence of carbon addition on the s martensitic transfometion and shape memory effect (SME) in Fe-Mn-Si based alloys. At first, a critical review is given on the development, characteristics and the mechanism of shape memory in Fe-Mn-Si based alloys. Various effects on the alloys, such as annealing temperature, prestrain and deformation temperature, thermal and thermomechanical cycling on the e martensitic transformation and the SME are discussed. It is concluded that a high strength matrix and a low stacking fault energy are the essential conditions required to obtain a good shape memory effect for the Fe-Mn-Si base alloys. The experimental work was carried out in two parts. In the first part, the effects of different carbon levels on the 6 martensitic transformation temperatures and 8 martensite morphology in Fe-20Mn-6Si alloys were examined by means of differential scanning calorimetry and optical microscopy. It was found that carbon strongly decreased the 'y->e martensitic transformation temperature, Ms. The addition of 0.3wt% carbon was found to reduce the Ms tenperature by up to 120K. The phase transformation hysteresis (As-Ms) increased with increasing the carbon content. On the other hand, the 8 martensite plates or bands became thinner as the carbon content increased.