Influence of the stress-induced martensite on the corrosion behavior of a β CuAlBe shape memory alloy

S. MONTECINOS; P. KLÍMEK; M. SLAMA; S. SUAREZ; S. SIMISON

Darmstadt

Congreso; Materials Science and Engineering-MSE2018; 2018

The influence of thestress-induced martensite on the corrosion behavior of a β CuAlBe shape memoryalloy after 60 days of immersion in a 3.5 % NaCl solution has been analyzed.The stress-induced martensite was retained in the sample after a load-unloadcompression cycle up to a pseudoelastic deformation of 4.5 %. Compression testswere carried out with a Shimadzu Autograph-DSS-10T universal testing machine atroom temperature, and a constant cross-head speed of 1 mm/min. The presence of martensiteneedles on a β matrix induced the localized corrosion of the β phase. Thecorrosion products and the morphology of the attack has been studied by meansof an Olympus BX60 microscope (OM), and a JEOL JSM-6460LV scanning electronmicroscope (SEM). To estimate the surface composition of different zones of thesamples, energy dispersive X-ray spectroscopy (EDX) analysis under SEM wasemployed. To identify the phase structure of the corrosion products film formedduring the immersion, X-ray diffraction (XRD) measurements were carried outusing a PANanalytical X?Pert Pro PW3373 and a PANanalytical X?Pert MPD X-raydiffractometers with normal and low incident angle. For investigation ofcrystallographic nature, TOF-SIMS analysis with C-TOF integrated on FIB-SEMTescan LYRA3 and an EBSD camera NordlysMax3were used. Theresults obtained in the present work suggest that the presence of the stackingfaults in the martensite phase would protect the martensite needles fromcorrosion. The corrosion of the alloy occurs by dealuminization, where β phaselocated in the areas between the needles of martensite is dissolved due to thepreferential loss of aluminum. From the EBSD results, it is proposed that themechanism of dealloying is dissolution of the alloy and redeposition of copper.