A new method to measure volume resistivity during tension for strain rate sensitivity in deformation and transformation behavior of Fe-28Mn-6Si-5Cr shape memory alloy

Abstract

This paper is concerned with the measurement method of volume resistivity in Fe-based shape memory alloy (Fe-SMA) during tensile tests using the circuit with a higher precision based on the Kelvin double bridge. In order to evaluate an amount of martensite associated with shape memory effect (SME), especially at higher deformation rate, it is convenient to capture the change in volume resistivity, which has a correlation with the amount of martensite. On the other hand, it is necessary to consider rate sensitivity of martensitic transformation behavior which is the key of SME as well as deformation behavior in Fe-SMA because the alloy is unavoidable to deform at higher strain rate. In this study, at first, a circuit with a higher precision based on the Kelvin double bridge is assembled. Then, tensile tests of Fe-28Mn-6Si-5Cr alloy at different strain rates are conducted by using two different testing apparatuses such as the conventional material testing machine and impact testing machine based on the split Hopkinson pressure bar technique. The rate sensitivity of the volume resistivity in Fe-SMA is experimentally captured by using the assembled circuit during the tensile testing at various strain rates. Shape recovery strain due to SME is measured by heating the specimens deformed quasi-statically at various strain rates up to above reverse transformation temperature.