Thermomechanical processing effects on the structure and properties of Fe-based SMAs. II. Evolution of damping behavior

The present paper analyses the effects of five different heat treatment temperatures, between 973, 1073, ... and 1373 K as well as two mechanical alloying (MA) fractions, 0 and 40 vol. %, on the evolution of damping behavior of an Fe-Mn-Si-Cr-Ni Shape Memory Alloy (SMA) obtained by powder metallurgy (PM). From the 10 types of samples, rectangular specimens were cut by wire-spark erosion for dynamic mechanical analysis (DMA) tests. DMA tests were performed by temperature scans (TS) and strain sweeps (SS). TS were applied between room temperature (RT) and 673 K, at constant amplitude, and thus enabled determining the temperatures of internal friction maxima associated with antiferromagnetic-paramagnetic transition (Néel temperature), A50N, and ε-martensite reversion to γ-austenite, A50ε, as a function of MA'ed fraction and HT temperature. SS were applied during three cycles with increasing strain amplitude and performed at three temperatures: (i) T1=RT; (ii) T2A50ε. The effects of HT temperature and MA'ed fraction on storage modulus (E') values were emphasized for each of the three temperatures T1,2,3. An E'-plateau was observed and associated with the formation of ε stress induced martensite, during DMA-SS.