Iranian Journal of Materials Science and Engineering

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In situ Al2024- Mg₂Si composite was fabricated by spark plasma sintering (SPS) of reactive powder. Reactive powder was obtained from mechanical alloying (MA) of elemental powders. Clad layers of in situ composite were fabricated on Al substrates by spark plasma sintering (SPS). Structural evolution during MA process and after SPS was investigated by X-ray diffractometery (XRD). Scanning electron microscopy (SEM) was utilized to study the microstructure of sintered samples. Hardness and tensile behavior of sintered samples were investigated. The results showed that SPS of mechanically alloyed unreacted powder can result in the in situ formation of Mg₂Si and Mg₂Al₃ within the Al matrix. SPSed clad layer showed a sound and clear interface to the Al substrate with a hardness of about 140 HV. Sintered in situ composite exhibited a tensile strength of 288 MPa.

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In this study, the effect of annealing treatment on microstructure and mechanical properties of Nb-10Hf-1Ti wt.% produced by Spark Plasma Sintering (SPS) was investigated. Scanning electron microscope (SEM), optical microscopy, X-ray diffraction analysis, hardness, and uniaxial tension test were used. Annealing treatment was carried out in a vacuum of 10^-3 Pa at 1150 °C for 1, 3, 5, and 7 hours and in an argon atmosphere at 1350 °C for 5 hours. Internal oxidation and subsequent hafnium oxide formation causes the hardening of the C103 alloy and drastically increases hardness and tensile strength. Although HfO₂ particles formed in the grain boundary cause brittleness and cleavage fracture of samples. Volume fraction, particle size, and mean interparticle spacing of oxides significantly change by annealing and subsequently the mechanical properties are affected. The SPSed sample at 1500 ℃ is softened by annealing at 1150 ℃ for 5 hours and its hardness and yield strength are reduced from 303 Hv to 230 Hv and 538 MPa to 490 MPa respectively. While annealing at 1350 ℃for 5 hours increases hardness and yield strength increases to 343 Hv and 581 MPa. 

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In this study, aluminum matrix composites reinforced with Al₂O₃ and SiC nanoparticles, and graphene nanoplatelets produced by Spark Plasma Sintering (SPS) were studied. The microstructural and mechanical properties of the composites were evaluated by changing the amounts of the reinforcing materials. The SEM images showed that the reinforcing particles were more distributed in the grain boundary regions. According to the results, the addition of alumina and SiC to the matrix caused an increase in the composite density whereas the composite density decreased by adding graphene nanoplatelets. The highest relative density of 96.3% was obtained for the composite containing 2 wt% Al₂O₃. The presence of the reinforcing particles increased the hardness of all the samples compared to the pure aluminum (39 HV). The composite containing 1 wt.% Al₂O₃, 0.7 wt.% SiC, and 0.3 wt.% graphene showed the highest hardness of 79 HV. Moreover, the plastic deformation of the specimens decreased and the slope of the plastic region increased by adding the reinforcing particles to the matrix.

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There is a global need to develop engineering materials to address the increasing demands in various industries. Spark plasma sintering (SPS) is one of the most distinguished powder metallurgy techniques, offering the opportunity for the fabrication of different types of materials. This work emphasizes optimizations of the important process parameters, including temperature, pressure, and holding time, involved in the SPS of the WC, WC-Co, and WC-Cr, as well as assessing the influence of the content of the Co (6-24 wt.%) and Cr (0.2-1 wt.%) binders on the overall characteristics of the SPS-ed cermets. The results illustrate that the process parameters highly affect the physicomechanical properties of the SPS-ed WC, where the most appropriate conditions from a physicomechanical viewpoint are obtained at a sintering temperature of 1700 °C, a pressure of 80 MPa, and a holding time of 5 min. The included Co binder reduces the optimum temperature and pressure down to 1200 °C and 70 MPa, respectively. The addition of the Co improves the final properties of the WC irrespective of its content. The highest tribomechanical properties are attained when 18 wt. % of Co is added. Similar to that of Co, the incorporation of Cr into the WC increases the tribomechanical performance. In general, the use of Co and Cr metallic binders seems a useful strategy to promote the overall properties of the SPS-ed WC.

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This study successfully synthesized the CoCrFeNiMn high-entropy alloy (HEA) using a two-step powder metallurgy approach: mechanical alloying (MA) followed by spark plasma sintering (SPS). The research investigated the effects of processing parameters, specifically MA duration and SPS temperature, on the alloy's microstructure, densification, and mechanical properties. X-ray diffraction (XRD) analysis after 25 hours of MA (ball-to-powder ratio of 10:1) confirmed the formation of a single-phase face-centered cubic (FCC) solid solution. Scanning electron microscopy (SEM) images revealed significant powder particle refinement, with average particle sizes decreasing from initial micrometers to sub-micrometer ranges. The alloyed powders were then consolidated via SPS at temperatures of 800°C, 900°C, and 1000°C (40 MPa, 10 min in argon). Detailed analysis of the sintered samples showed relative densities ranging from 95.78% to 96.77%, with the highest density (96.77%) achieved at 1000°C. Vickers microhardness measurements exhibited a peak hardness of 446 HV at 900°C, with a decrease to 420 HV at 1000°C, primarily due to grain growth. This research establishes the combined MA and SPS approach as effective for producing high-density, high-hardness HEAs, underscoring the critical role of processing parameters in tailoring their final properties.