عنوان	Microstructural characterization and quantitative phase analysis of Ni-rich NiTi after stress assisted aging for long times using the Rietveld method
نوع پژوهش	مقاله چاپ شده
کلیدواژه‌ها	NiTi shape memory alloy, Rietveld method, Quantitative phase analysis, Ni3Ti precipitates
چکیده	Abstract The present work was aimed to quantitatively analyze the phases in the Ni-rich NiTi shape memory alloy which was aged at different temperatures of 470, 500 and 530 °C for 11, 38, 196 and 536 h. The aging treatment was done while applying various stress values. The phase transformation behavior of prepared specimens was analyzed using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) at ambient temperature and 75 °C. The weight percent of the different phases was measured by the Rietveld refinement method using MAUD software. The quantitative phase analysis and transmission electron microscopy (TEM) images show that the amount of Ni4Ti3 precipitates is increased in the specimens aged under stress. Furthermore, the Ni4Ti3 metastable precipitates are transformed to Ni3Ti2 and Ni3Ti stable phases after a long period aging under 120 MPa for 536 h and the various variants of precipitates are not affected by applied stress after long periods of aging.
پژوهشگران	ویدا خلیلی (نفر سوم)، جعفر خلیل علافی (نفر دوم)، حجت ناجی (نفر اول)