M.Dovchinvanchig Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 8, Issue 7 (Part -IV) July 2018, pp 01-03 www.ijera.com DOI: 10.9790/9622-0807040103 1 | Page Microstructure and phase transformation of nearly equiatomic Ni-Ti binary shape memory alloy M.Dovchinvanchig, O.Amartuvshin, P.Enkhtsetseg, B.Bolormaa, Ya.Gangantogos, B.Munkhjargal (Department of Mathematics, Physics and Information Technology, School of Engineering and Technology Mongolian University of Life Sciences, Ulaanbaatar, Mongolia Corresponding Author : M.Dovchinvanchig ABSTRACT The phase transformation and microstructure behavior of Ni-Ti shape memory alloy was investigated by scanning electronic microscope, X-ray diffraction and differential scanning calorimetry. The results showed that the microstructure of Ni-Ti binary alloy consists of the NiTi 2 phase and the NiTi matrix phase. One-step phase transformation was observed alloy. Keywords - Shape memory alloy, microstructure, phase transformation, --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 11-07-2018 Date of acceptance: 25-07-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Ni-Ti shape memory alloys (SMAs) is a very important material because it owns unique shape memory effect and super-elasticity behaviors. Today this kind of material has been used in many different fields, especially in engineering and medical application[1]. Current research interest on SMA are mainly controlling the martensitic transformation temperature and improving the shape memory effect for their applications. The effect of martensitic transformation, super-elasticity and shape memory effect have been studied widely. Phase transformation behavior is strongly dependent on alloying elements, composition, precipitates and heat treatment. Moreover, the microstructure and phase transformation temperature of the Ni-Ti binary alloys have also been studied using scanning electron microscopy(SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The Ni-Ti binary alloys was found decreaced and increase the phase transformation temperature and change the phase transformation sequence. II. EXPERIMENTAL The Ni-Ti alloy were prepared by melting each 10g of raw materials with different nominal compositions (99.9 mass% sponge Ti, 99.7 mass% electrolytic Ni) in a nonconsumable arc-melting furnace using a water-cooled copper crucible. The alloy in denoted Ni-Ti alloy, respectively. Are- melting was repeated five times to ensure the uniformity of composition. The specimens are spark- cut from the ingots and solution –treated at 850 0 C for an 1hour in a vacuum quartz tube furnace. Subsequently the specimens were quenched using water. Thereafter, the specimens are mechanically and lightly polished to obtain a plain surface. The phase transformation temperature of Ni-Ti alloy were determined by DSC using a TA Q2000 calorimeter. The temperature range of heating and cooling was from -30 0 C to 155 0 C, and the scanning rate of heating and cooling was 10 0 C/min. SEM observations were conducted using a FEI Quanta 650 FEG equipped with EDS analysis systems made by Oxford. An XRD experiment was conducted using a D/MAX-2500PC X-ray diffractometer. III. RESULTS AND DISCUSSION 3.1. Microstructure of Ni-Ti alloy Fig.1 depicts the SEM images of Ni-Ti alloy. There are two different morphologies, namely, black phase and matrix can be identified in the SEM image. The black phase is in irregular shape and distributed randomly in the matrix. To identify the phase structure, EDS analysis was conduced in SEM. The compositions of Ni-Ti alloy are shown in Table.1 The Ti:Ni ratio in the matrix of all Ni-Ti alloy is measured to be near 1. Thus, the matrix can concluded to be NiTi phase. The Ti:Ni ratio in the black phase of Ni-Ti alloy is measured to be near 2:1. By XRD analysis, there is a NiTi2 phase in Ni-Ti. Thus, the black phase can be concluded to be NiTi2. RESEARCH ARTICLE OPEN ACCESS