Abstract
Nanocrystalline Ni(50-x)Ti50Cux(X = 5, 9 wt%) alloys were successfully produced by mechanical alloying. Mechanical activation was performed at different milling times under a high purity argon (99.998 vol%) atmosphere. Phase analysis and structural features of the samples were examined by X-ray diffraction (XRD). Results revealed that NiTiCu (B2) phase was achieved after 600 min of milling. The formation of this phase was mostly related to the critical factors in determining the site replacement of elements in Ni-Ti-Cu ternary system. After 600 min of milling, the average crystallite size and lattice strain of the samples were about 5 - 10 nm and 1.057% - 1.967%, respectively. Evaluation of the full width at half maximum (FWHM) values for all the samples indicated the occurrence of anisotropic line broadening. The determined amounts of crystallinity revealed that the fraction of crystalline phase decreased with increasing weight percentage of copper up to 9% and reached a minimum value after 600 min of milling. The lattice parameters and the unit cell volume of the milled samples were always larger than the standard values. In addition, lattice parameter deviation influenced by the weight percentage of copper. Based on the obtained data, mechanical alloying process can be used for production of nanocrystalline NiTiCu alloys with different structural features.
Highlights
NiTi shape memory alloys (SMAs) have been widely utilized in different fields of aerospace and medicine due to their superior shape memory effect and higher superelasticity compared to other shape memory alloys [1]
Phase analysis and structural features of the samples were examined by X-ray diffraction (XRD)
The determined amounts of crystallinity revealed that the fraction of crystalline phase decreased with increasing weight percentage of copper up to 9% and reached a minimum value after 600 min of milling
Summary
NiTi shape memory alloys (SMAs) have been widely utilized in different fields of aerospace and medicine due to their superior shape memory effect and higher superelasticity compared to other shape memory alloys [1]. Several methods have been developed to synthesize NiTi-based alloys such as conventional powder metallurgy, self-propagating high temperature synthesis (SHS), shock synthesis and mechanical alloying (MA) [5]. Among these methods, MA is a powder technique that allows production of homogeneous materials from blended elemental powder mixtures. MA is a powder technique that allows production of homogeneous materials from blended elemental powder mixtures In this method, melting is not essential and the products have nanostructural characteristics as a result MA has been applied to produce all material classes including metals, ceramics, and polymers [6]. There are a few papers about the structural characterization of the nanocrystalline Ni(50−X)Ti50CuX alloys produced by MA process [8,9]
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