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High Entropy Alloys in Bulk Form
Published in T.S. Srivatsan, Manoj Gupta, High Entropy Alloys, 2020
Reshma Sonkusare, Surekha Yadav, N.P. Gurao, Krishanu Biswas
MA is followed by sintering to obtain the final product in the bulk form. For sintering, both the conventional sintering route (such as hot isostatic pressing (HIP), hot pressing (HP), etc.) or the spark plasma sintering route can be used. However, spark plasma sintering (SPS) is preferable to other sintering techniques due to its shorter sintering time, high heating rate, short holding time, limited grain growth, better relative density, and protective environment. SPS uses the pulsed DC current (up to 5,000 A) and uniaxial pressure (30–100 MPa) to achieve the bulk form with stable phases and significant mechanical properties. Spark plasma sintering opens up the possibilities to synthesize the complex microstructure with suitable properties. After solidification and casting, MA followed by SPS is widely used for bulk preparation of HEAs and HEA composites [64].
Synthesis and Characterization of Copper–Ruthenium Composites
Published in Ajay Kumar Mishra, Lallan Mishra, Ruthenium Chemistry, 2018
Rasidi Sule, Iakovos Sigalas, Joseph Kwaku Ofori Asante, Peter Apata Olubambi
Spark plasma sintering (SPS) also known as field-assisted sintering technology (FAST) is currently a widely used sintering technique employing current-activated consolidation. The spark plasma sintering process is based on the principle of the electrical spark discharge phenomenon. Spark plasma sintering uses high energy, low voltage, pulsed DC current, and uniaxial pressure to consolidate metallic/ceramic powders (Munir et al., 2006). The accurate control of sintering energy as well as high sintering speed makes SPS a promising technique of producing highly dense materials with controlled grain growth (Suárez et al., 2013). However, there is a similarity between hot pressing and spark plasma sintering as both techniques are usually involve a uniaxial press coupled with a heating devices. In hot press technique, the sample is heated by radiation from enclosed furnace through external heating elements. However, in SPS, the joule effect caused by a pulsed direct current lead to very rapid and efficient heating (Suárez et al., 2013). A schematic of the SPS the showing tooling set up is given in Fig. 5.8.
Fabrication Routes for Nanostructured TE Material Architectures
Published in D. M. Rowe, Materials, Preparation, and Characterization in Thermoelectrics, 2017
Muhammet S. Toprak, Shanghua Li, Mamoun Muhammed
CoSb3 powders have been prepared by vacuum melting and annealing using high-purity metallic elemental rectants.16 Spark plasma sintering (SPS) is a sintering method where direct current is passed through the sample during compaction, reaching very high densification values with minimum exposure to elevated temperatures and pressures. High-performance NS bulk skutterudites YbxCo4Sb12 have been prepared by combining the melt-spinning technique with SPS. Prepared polycrystalline ingots with desired stoichiometry using the traditional method (melt + quench + annealing + SPS) were inductively melted in a quartz tube and the melt is ejected on a chilled Cu wheel where it rapidly solidified. Formed ribbons were then collected and loaded into a graphite die and sintered by the SPS method. As a result, NS materials with grain size of 100–200 nm and finer structure with nanocrystals of 10–20 nm were obtained as can be seen from the micrographs presented in Figure 17.1.17
Fundamental principles of spark plasma sintering of metals: part I – Joule heating controlled by the evolution of powder resistivity and local current densities
Published in Powder Metallurgy, 2019
‘Spark Plasma Sintering’ (SPS) is the most common name for a powder consolidation technology that uses a pulsed electric current to heat the powder compact and simultaneously accelerates its densification by applying an uniaxial mechanical pressure. As both the existence of sparks and plasma have been questioned [1, 2] and with densification being attributed to plasticity and creep [3–6], many other names have been proposed, like field-assisted sintering technology (FAST), pulsed electric current sintering (PECS), and so on [7]. Even though this publication will, together with two following parts, show that there is indeed neither spark nor plasma, the term SPS is nevertheless used as it is the one name everybody active in this field immediately recognises.
Development of TiCN-Co-Cr3C2-Si3N4-based cermets with improved hardness and toughness for cutting tool applications
Published in Powder Metallurgy, 2023
Balasivanandha Prabu Shanmugavel, Sri Harini Senthil Kumar, Chellammal Nandhini Aruna, Madhi Varshini Ramesh
Spark Plasma sintering (SPS) is a process used to consolidate powders into solid parts. This powder metallurgy combines heat and pressure to sinter powders together. The process is performed in a vacuum, in which the powders are placed in a die and subjected to electric current. This causes a spark to be generated between the powders, which raises the temperature of the powder to the sintering point. Pressure is then applied to consolidate the powder into solid parts. SPS has the advantage of a relatively short sintering time, high sintering density and excellent properties of the sintered materials. SPS can be used to sinter a wide range of materials, including metals, ceramics and their composites as well [2].
Mechanical and microstructural properties of titanium/hydroxyapatite functionally graded material fabricated by spark plasma sintering
Published in Powder Metallurgy, 2018
N. Omidi, A. H. Jabbari, M. Sedighi
Functionally graded materials (FGM) are a new type of advanced materials consisting of the continuous or discontinuous gradient in their compositions or structures [1,2]. Depending on the type of materials and FGM applications, several methods are used to fabricate FGMs such as powder metallurgy, casting, freeze-form extrusion, high-gravity combustion synthesis, roll bonding, remelting and sedimentation process, and centrifugal casting [3–8]. Since each method has its own advantages and disadvantages, it is hard to define the best method to produce FGMs. However, among all of these methods, powder metallurgy is one of the most interesting method for FGMs fabrication [1]. This method is used with two different approaches: pressure less sintering and sintering with applying pressure. The spark plasma sintering (SPS) is a high-speed sintering method, simultaneously introducing heating and mechanical pressure to the material. This method is widely used to consolidate ceramics, metals, composites and FGM. It has several advantages in comparison to other conventional sintering methods such as decreasing sintering temperature and time. For instance, for a titanium/hydroxyapatite (Ti/HA) composite, temperature and time decrease from 1300°C to 850°C and 90 min to 5 min, respectively. This reduction prevents decomposition of HA and the reaction between titanium and HA [9,10]. In addition, in the conventional cold pressing process, for pressure less sintering method, the friction force between die and powders has a negative effect on mechanical and microstructural properties. In other words, by receding from a punch, compressive force reduces dramatically. As a result, the pressure of cold pressing is not uniform along the axial axes of the compacted samples.