Investigation of the change in the physical properties of niti shape memory alloys by adding cobalt element

SUMMARY INVESTIGATION OF THE CHANGE IN THE PHYSICAL PROPERTIES OF NITI SHAPE MEMORY ALLOYS BY ADDING COBALT ELEMENT In this study, The NiTi shape memory alloys which doped with 2, 3, 4, 5, and 6 at.% of cobalt element were melted by using arc-melting technique and cooled down to room temperature naturally. To make all contribution elements spread equally in the prepared alloy's ingots, they were kept at 1050 oC for 24h in a furnace at air atmosphere. By using DSC (Differential Scanning Calorimetry), x-ray diffractometer, optical microscope, SEM-EDX, and PPMS equipment each crystal structure of alloys, the microstructural phases, variation rate in chemical composition, and magnetization properties of the samples determined, respectively. The results showed that alloys with 2, and 3 at.% of cobalt content has martensite phase in room temperature while the others at the same temperature had austenite phase. The enthalpy change found to have different situation for each categories, such that its value increase in martensite phase-alloys, whereas, this value decrease with increasing Co-additive in austenite phase-alloys. Also, magnetization measurement at room temperature showed that austenite phase-alloys have higher magnetization compared with martensite phase-alloys. Keywords: Phase transformation; Shape Memory Alloy; Cobalt element; Ti2Ni phase; magnetization properties; NiTi alloy.