HVEM OBSERVATION OF MICROSTRUCTURES IN Fe-Mn-Si BASED SHAPE MEMORY ALLOYS AFTER HIGH SPEED DEFORMATION

摘要

Fe-Mn-Si based shape memory alloys deformed by a super high-speed roller were examined by HVEM after various heat treatments and mechanical tests. It has been revealed that the strong iron based shape memory alloy can be rolled down to 50 % in thickness reduction by use of Cu plates covering a foil specimen. Microstructures of as rolled and annealed specimens were examined with special interest in the refinement of crystal structure. Application of a 2-1/2 D method enabled us to visualize microscopic distribution of sub-grains and distribution of misorientations that play an important role in strengthening of these alloys. Effect of introduction of second phase particles on the strengthening has also been studied for the purpose of improving the shape memory property by structural refinement.