Open AccessThe effect of different at.% Ag elements on the wear rate of nitinol alloys fabricated using the casting method
Author(s) -
Saja Mohammed Hussein,
Khansaa D. Salman,
Ahmed A. Hussein
Publication year - 2020
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/987/1/012022
Subject(s) - shape memory alloy , materials science , pseudoelasticity , nickel titanium , austenite , alloy , casting , metallurgy , diffusionless transformation , martensite , phase (matter) , optical microscope , composite material , microstructure , scanning electron microscope , chemistry , organic chemistry
Shape memory alloys are considered smart alloys due to their properties, such as biocompatibility, superelasticity (SE) and shape memory effect (SME). These alloys are used in many applications (actuators, MEMS, biomedical and aerospace). In this work, the effect of adding the silver element to the NiTi alloy with different atomic percentages (zero, one, two and three at.% Ag) on mechanical properties, such as macrohardness and wear, was studied. The samples of this work were prepared by the casting method using a VAR furnace to obtain homogeneous shape memory alloys. The purity of the elements was Ni 99.2 %, Ti 99.7 % and Ag 99.99 %. In this work, many examinations were carried out to define the characteristics of the manufactured shape memory alloys, such as FESEM and OM, for microstructural analysis. Meanwhile, the mechanical properties were defined using macrohardness and wear tests. The results of the mechanical tests showed a slight impact in the percentage of the wear resistance and macrohardness at the point of increasing the silver element ratio to the binary alloy (NiTi). The photomicrographs of the OM and FESEM examinations showed that the Ag element is homogeneously distributed in the NiTi matrix. In addition, the FESEM examination showed the emergence of the martensite phase, austenite phase and some impurities. The results of the DSC test showed the degrees of the phase transformation for each alloy, and the SME recovery rate of 89.99% was achieved. Furthermore, the surface topography was analysed using an optical microscope for all the tested samples. The obtained results emphasised that the movement between the disc and the pins leads to a rise in the friction temperature and the formation of the layer of oxidation. These oxidation layers will be ploughed and uprooted to create many grooves at the surface of the samples. Hence, these grooves are similar for all samples and increased with increasing loads.