Effect of Ta content and sintering temperature on characteristics of nanocrystalline Cu-Ta nanocomposite
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Effect of Ta content and sintering temperature on characteristics of nanocrystalline Cu‑Ta nanocomposite Roohollah Rahmanifard1 · Seyed Meysam Javidan1 · Mohsen Asadi Asadabad2 Received: 4 April 2020 / Accepted: 5 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this study, the microstructural, physical and mechanical properties of the nanocrystalline Cu-Ta material synthesized by mechanical milling and subsequent sintering were investigated affected by Ta content and sintering temperature. Scanning electron microscope and X-ray diffraction results showed that increasing Ta content from 1 to 5 wt% changed the material behavior during milling and resulted in reduction of powder particle size and crystallite size. For the sintered specimens, addition of Ta decreased the electrical conductivity due to reduced density and increased electron scattering effect while micro-hardness of Cu matrix was promoted. The higher sintering temperature about 850 °C also increased density and provided more segregation of Ta which was led to improvement in both micro-hardness and electrical conductivity of Cu-Ta composite. In addition, a comparison between sintering process at 850 °C by SPS method and conventional cold pressingsintering revealed that SPS has a high potential to enhance physical and mechanical properties. Keywords Cu-Ta · Nanocomposite · Immiscible alloys · Electrical conductivity · Ta content · Sintering temperature
1 Introduction Thermal stability of the nanocrystalline materials is a serious challenge to their development [1]. To stabilize the nanostructured grain or slow down the grain growth at high temperatures, the solution is the reduction of either grain boundary energy or grain boundary mobility. In the former, solute atom segregation along the grain boundaries deceases driving force of the grain growth which is known as thermodynamic stabilization. In the second case called as kinetic stabilization, solute drag forces or pining effect of the secondary phase are the factors which can reduce the mobility of grain boundary [2–4]. As the mobility of boundaries is a temperature-dependent factor and obeys from Arrhenius relationship, and in the other hand, at high temperatures the possibility of secondary phase coarsening cannot be also excluded, thus the thermodynamic method can stabilize the
* Roohollah Rahmanifard [email protected] 1
School of Advanced Technologies, Iran University of Science and Technology, Tehran, Iran
Nuclear Science and Technology Research Institute, Tehran, Iran
2
structure more effectively compared to the kinetic method [4, 5]. Incorporation of immiscible elements into alloy composition can induce a potential to produce the materials with high strength and good thermal stability. Segregation of these elements on the grain boundaries reduces the free energy required for grain growth. The mobility of boundary can be also decreased by solute drag force of the alloying elements. Additionally, the presence of these particles can act as the
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