Effect of milling time on the structure, micro-hardness, and thermal behavior of amorphous/nanocrystalline TiNiCu shape memory alloys developed by mechanical alloying

Abstract

In the present paper, the effect of milling process on the chemical composition, structure, microhardness, and thermal behavior of Ti-41Ni-9Cu compounds developed by mechanical alloying was evaluated. The structural characteristic of the alloyed powders was evaluated by X-ray diffraction (XRD). The chemical composition homogeneity and the powder morphology and size were studied by scanning electron microscopy coupled with electron dispersive X-ray spectroscopy. Moreover, the Vickers micro-indentation hardness of the powders milled for different milling times was determined. Finally, the thermal behavior of the as-milled powders was studied by differential scanning calorimetery. According to the results, at the initial stages of milling (typically 0-12. h), the structure consisted of a Ni solid solution and amorphous phase, and by the milling evolution, nanocrystalline martensite (B19') and austenite (B2) phases were initially formed from the initial materials and then from the amorphous phase. It was found that by the milling development, the composition uniformity is increased, the inter-layer thickness is reduced, and the powders microhardness is initially increased, then reduced, and afterward re-increased. It was also realized that the thermal behavior of the alloyed powders and the structure of heat treated samples is considerably affected by the milling time. © 2013 Elsevier Ltd

Shape Memory NiTi and NiTiCu Alloys Obtained by Spark Plasma Sintering Process

“…For the NiTiCu samples were obtained similar results both for mechanically alloyed (S2) and unalloyed (S1) samples, these being in agreement with the literature data [14,15]. Also, the existence of a Ti 2 (Ni, Cu) phase can be attributed to the presence of a considerable amount of Tiregions in the amorphous phase produced during the milling process.…”

Preliminary investigation on development of functionally graded cemented tungsten carbide with solid lubricant via ball milling and spark plasma sintering

“…This condition is significant in allowing WC particles to make bond in consolidation stage. 30,32,33…”

Fabrication of manganese-aluminum bronze as a shape memory alloy by accumulative roll bonding process

“…So that, using heat treatment, the corrosion current density is decreased from 6.5 μA/cm 2 to 1.78 μA/cm 2 ( Table 1). The corrosion current density, i corr (µA/cm 2 ), is related to the corrosion rate, P i , through the following empirical equation [40]: P i = 22.85 i corr (2) According to the equation, the corrosion rate of the Cu-Al-Mn alloy is decreased from 148.52 µm/year to 40.67 µm/year for the composite and heat-treated alloy, respectively.…”

“…Shape memory alloys (SMAs) have unique properties which make them a multifunctional material for different applications [1]. Among shape memory alloys, NiTi compounds are widely used in medical and engineering applications, due to their shape memory effect (SME), superelasticity and biocompatibility [2,3]. However, the low transformation temperature and excessive production cost of NiTi alloys reduce their applications, particularly for high-temperature uses [1,4].…”