Abstract
The influence of mechano-ultrasonic activation (MUA) and nano-additives (carbon nanotubes-CNT) on the interaction pathway of nickel–aluminum powder mixture at high heating rates was investigated. The optimum conditions of the mechano-ultrasonic activation, along with the phase and structure formation peculiarities of nickel–aluminum and nickel–aluminum–carbon nanotubes mixtures by thermal analysis method, the so-called high-speed temperature scanner (HSTS), were found out. The optimum duration of mechanical and ultrasonic activation aiming to achieve homogeneous distribution in the agitated mixtures was determined. A shift in characteristic temperatures of MUA mixtures by the influence of both heating rate and ultrasound on the Ni + Al interaction pathway for the mechano-activated (1, 3, 5 min) and 1 wt% CNT containing mixtures was observed. The formation patterns of NiAl + Ni3Al mixture or pure NiAl phase was manifested according to the interaction mechanism (depending on solid–liquid or solid–solid state of intermediates). The effective activation energy values for the Ni + Al exothermic reactions of all studied systems were determined by the isoconversional method of Kissinger.
Highlights
Nickel–aluminum intermetallics, encompassing the compositional region between 40%and 80% of nickel, have attracted considerable interest owing to a favorable combination of properties, such as high melting point, low weight, high resistance to corrosion, and high-temperature strength [1–3]
The utilization of mechanical activation (MA) allows us to overcome the challenges that arise in the melting or casting processes of nickel aluminides [10,11]
99.8%) and aluminum (ASD-4, Kyiv, Ukraine, particle size < 40 μm, purity 99.9%) powders were used as raw materials, and carbon nanotubes were used as nano-additives (CNT, from tens of nanometers to several microns in size produced by [22])
Summary
80% of nickel, have attracted considerable interest owing to a favorable combination of properties, such as high melting point, low weight, high resistance to corrosion, and high-temperature strength [1–3]. The mechanical activation (MA) [4,5] and self-propagating high-temperature synthesis (SHS) are the most widely investigated techniques [6–8] among the versatile methods for manufacturing nickel aluminides. MA has already emerged as one of the productive and mature techniques for the solid-state synthesis of the nanocrystalline intermetallics uniform by the phase composition [9]. MA is utilized to attain grain refinement, hardening and alloying through secondary phases, which have been found to be effective strategies to improve the mechanical behavior of these intermetallic compounds. The utilization of MA allows us to overcome the challenges that arise in the melting or casting processes of nickel aluminides [10,11].
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