Project description

The proposal explores the factors that favor the emergence of super-elasticity (SE) in SMA FeMnAlNi, comparing their reaction with the superelastic behavior of the FeNiCoAlTaB alloy taken as a reference. In the first stage of the project, vacuum-induction melt ingots will be produced in a cold crucible with the compositions: Fe40.95 Ni28 Co17 Al11.5 Ta2.5 B0.05 and Fe43.5Mn34Al14; 15; 16Ni7; 7.5; 8. The billets will be cut, hot rolled up to thickness t = 0.5-1 mm and thermally treated to favor the abnormal growth of crystalline grains at SMA FeMnAlNi. AMF FeNiCoAlTaB will be cold rolled and put in solution (1250 ° C) to produce a strong texture {035}. After thermal treatment, the average size (D) of the grains will be determined by optical microscopy. The purpose of thermal treatment is to obtain a bamboo oligocrystalline structure characterized by D / t> 1 and the absence of triple junctions of grains. From the oligocrystalline samples, in the second phase of the project, samples for mechanical testing and mechanical-dynamic analysis (DMA) will be sampled. Tensile loading/unloading tests will be performed at different temperatures and the deformation stress curves will be analyzed. The reversible force variation with the amplitude of the deformation during dynamic cycles will be analyzed by deformation swings on the DMA with a dual lever test attachment. In the third stage of the project, the FeNiCoAlTaB and FeMnAlNi samples, which developed SE on traction, will undergo thermal and structural analysis. The first will be performed by differential scanning calorimetry to determine critical transformation temperatures and the second by X-ray diffraction, electron beam scanning coupled with retarded electron diffraction and electron microscopy through transmission, to observe the presence of coherent precipitates and to correlate their morphological fluctuations with technological factors.