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Densification of Consolidated Products
Published in Anshuman Patra, Oxide Dispersion Strengthened Refractory Alloys, 2022
The sintering process can be accelerated with a reduced sintering temperature by the liquid phase sintering method [3]. Liquid phase sintering involves the formation of a liquid phase in which the solid constituents are soluble. Therefore, the effectiveness of the liquid phase depends on the solubility of the solid constituents in the liquid. The wetting of the solid phase by the liquid and the capillary pressure exerted by the liquid phase are effective in particle bonding. If the solid has no solubility in liquid, the solid-state sintering is dominant and the liquid assists in densification by sealing the pores [4, 5]. The liquid-phase sintering process and the progress of densification with sintering time are described in Figure 6.2 and Figure 6.3 respectively. In the initial step, the solid state sintering occurs which leads to densification. With the progress of sintering, the liquid phase moves between the grains and grain readjustment occurs, followed by solution-reprecipitation and finally solid state sintering, which induces slow densification [6].
Additive Manufacturing Processes Utilizing Powder Bed Fusion Technique
Published in Manu Srivastava, Sandeep Rathee, Sachin Maheshwari, T. K. Kundra, Additive Manufacturing, 2019
Manu Srivastava, Sandeep Rathee, Sachin Maheshwari, T. K. Kundra
In liquid phase sintering, one of the powders is in a partially molten state thereby acting as a gluing material for another one which is a solid. It is the most widely utilized binding technique owing to its high-quality results. This technique also finds wide utilization in powder metallurgy applications. The partial melting technique is used in more than one way for AM fusion applications. A classification was proposed by Kruth et al. [5] to distinguish between various techniques:Separate binder and structural materials that can be composite or coated particlesIndistinct binder and structural materials.
Liquid-Phase Sintering
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
Our discussion of the sintering process has so far been concerned with solid-state sintering in which the material remains entirely in the solid state. However, in many ceramic systems the formation of a liquid phase is commonly used to assist in the sintering and microstructural evolution. Usually the purpose of liquid-phase sintering is to enhance densification rates, achieve accelerated grain growth, or produce specific grain boundary properties. The distribution of the liquid phase and of the resulting solidified phases produced on cooling after densification is critical to achieving the required properties of the sintered material. Commonly, the amount of liquid formed during sintering is small, typically less than a few volume percent (vol%), which can make precise control of the liquid composition difficult. In some systems, such as Al2O3, the amount of liquid phase can be very small and so difficult to detect that many studies that were believed to involve solid-state sintering actually involved liquid silicate phases, as later revealed by careful high-resolution transmission electron microscopy.
Sintering behavior and mechanical properties of calcium phosphate–alumina composite porous scaffolds
Published in Advanced Composite Materials, 2023
We proposed a novel high-performance scaffold composite of calcium phosphate and alumina and investigated the effects of the sintering temperature on the microstructure, shrinkage, crystalline structure, and mechanical properties. At high temperatures, liquid-phase sintering occurs, which significantly changes the microstructure and reduces the closed porosity. The addition of alumina accelerated the phase transformation of HA, resulting in an α-TCP–alumina composite. These results also suggest that a mixture of calcium phosphate and alumina may have formed at a sintering temperature of 1550 °C. The Young’s modulus and compressive strength increased with increasing sintering temperature, and the compressive strength of st1550 increased significantly owing to the reduction in stress concentration caused by the smoothening of the microstructural surface. The calcium phosphate–alumina composite porous scaffold proposed in this study is considered an ideal artificial bone material that allows early bone formation inside the porous body.
Recovery of Al2O3/Al powder from aluminum dross to utilize as reinforcement along with graphene in the synthesis of aluminum-based composite
Published in Particulate Science and Technology, 2023
Shashi Prakash Dwivedi, Shubham Sharma
Sintering is the procedure of heating the substance to the melting temperature or below the melting temperature but high enough to permit the fusion or bonding of particles under a shielding atmosphere to prevent oxidation (Ling et al. 2021). There are two types of sintering processes namely: liquid-phase sintering, and solid-state sintering. When a liquid phase is present in the powder compact during sintering called liquid phase sintering. Solid-state sintering takes place while the powder compact is densified at the sintering temperature entirely in a solid state (Petit et al. 2021). Different types of sintering such as liquid phase sintering, spark plasma sintering, plastic sintering, and microwave sintering are used to fabricate sintered products and still permit additional materials to be sintered. However, microwave sintering for structural applications is an extremely fine option for sintering and consolidating commercial materials. The advantages of the microwave sintering process are energy consumption, reduction in processing times, enhanced mechanical properties, and finer microstructure (Guillén et al. 2021; Z. Li, Ling, et al. 2021). The microwave sintering technique is mainly used for both metals and ceramics in almost vacuum. Surface contamination probability in the vacuum is negligible. Further, the formation of porosity is also negligible during this process (Q. Li, Yu, and Sun 2021).
Microstructural and mechanical characterisation of WC–Co alloys elaborated by liquid phase sintering and hot isostatic pressing: study of WC crystallites size evolution
Published in Canadian Metallurgical Quarterly, 2023
Hassiba Rabouhi, Dominique Eyidi, Youcef Khelfaoui, Abdelkrim Khireddine
Liquid phase sintering is a process for producing materials from powders having at least two components: one of them must melt at the sintering temperature to form a liquid phase which ensures the densification of the material after cooling [1]. This process is used to develop composites, a good example of which is cemented carbide WC–Co. The obtained microstructures consist of faceted WC grains inserted in a cobalt matrix. In industry, these materials are used as cutting tools because of the high hardness of the carbide and good toughness provided by the cobalt binder. To optimise mechanical properties of these materials, it is necessary to ensure maximum densification as well as a fine microstructure during development [2–4]. However, products obtained by liquid phase sintering are not always very dense and present two types of heterogeneities, namely that of WC and Co components and that of residual porosities [5]. These shortcomings lead to a limitation and dispersion of so-obtained materials mechanical characteristics [6]. To relieve these shortcomings, the sintering cycle is generally terminated by an increase of the gas pressure for a certain time in order to eliminate the residual porosity and improve the homogeneity of the final product [7,8]. In this perspective, we have sought in the proposed work to optimise the mechanical properties of cemented carbides by proceeding to the densification of WC–Co mixtures by hot isostatic pressing (HIP).