Showing papers on "Powder metallurgy published in 2022"

Effect of mixing method and particle size on hardness and compressive strength of aluminium based metal matrix composite prepared through powder metallurgy route

Abstract: Properties of metal matrix composites (MMCs) are affected by various process variables such as particle size of powders, the proportion of reinforcement material, mixing methods, sintering temperature, and duration. The significant drawback of stir casting is reinforcement segregation, which is too difficult to avoid. Hence, the powder metallurgy route is utilized to prepare Al-MMC. In the current work, aluminium-based MMC is fabricated with varying proportions of silicon carbide (SiC) as a reinforcement material. Mixing of powders is done using V-Blender and barrel mixer with three different mixing techniques and the mixing quality of prepared powders is assessed. A significant reduction of mixing time, i.e., more than 50%, is achieved through a novel barrel mixer as compared to a conventional V-blender. Two important properties, hardness and compressive strength of fabricated Al-MMC, are experimentally investigated. At the same time effect of the mixing technique is also studied, and it is evident that hardness and compressive strength improved when powders are mixed using a barrel mixer. Thus, a novel approach to powder mixing has been achieved. An increase in SiC proportion by 5% resulted in an increase in hardness by 14%. The average compressive strength of Al-MMC is highest when reinforcement content is 25%. Due to the uniform dispersion of particles achieved through barrel mixer, compressive strength of MMC is 8–20% higher than the strength of those MMC for which powders are mixed through conventional V-blender. A similar effect is observed in the hardness also, where the average hardness of MMC is 10–20% higher, for which powders are mixed through barrel mixer. Hence, the newly designed barrel mixer provides an effective solution for the quality mixing of powders through the powder metallurgy process for fabricating Al-MMC.

Plasma spheroidization of gas-atomized 304L stainless steel powder for laser powder bed fusion process

Abstract: Particles of AISI 304L stainless steel powder were spheroidized by the induction plasma spheroidization process (TekSphero-15 spheroidization system) to assess the effects of the spheroidization process on powder and part properties. The morphology of both as-received and spheroidized powders was characterized by measuring particle size and shape distribution. The chemistry of powders was studied using inductively coupled plasma optical emission spectroscopy for evaluation of composing elements, and the powder’s microstructure was assessed by X-ray diffraction for phase identification and by electron backscattered diffraction patterns for crystallography characterization. The Revolution Powder Analyzer was used to quantify powder flowability. The mechanical properties of parts fabricated with as-received and spheroidized powders using laser powder bed fusion process were measured and compared. Our experimental results showed that the fabricated parts with plasma spheroidized powder have lower tensile strength but higher ductility. Considerable changes in powder chemistry and microstructure were observed due to the change in solidification mode after the spheroidization process. The spheroidized powder solidified in the austenite-to-ferrite solidification mode due to the loss of carbon, nitrogen, and oxygen. In contrast, the as-received powder solidified in the ferrite-to-austenite solidification mode. This change in solidification mode impacted the components made with spheroidized powder to have lower tensile strength but higher ductility.

Effect of Tungsten Carbide Addition on the Microstructure and Mechanical Behavior of Titanium Matrix Developed by Powder Metallurgy Route

Abstract: The ambition of this research work is to evaluate the hardness and wear behavior of titanium alloy reinforced with tungsten carbide particle (WC) composite prepared by powder metallurgy route. Titanium alloy with 5 and 10 wt% tungsten carbide reinforced particle (WC) composites was manufactured through powder metallurgy technique. The hardness and wear properties of the composite are measured in hardness and wear tests. The microstructures of the composite are evaluated by utilized optical microscopy. The fabricated titanium composites exhibit improved hardness and wear resistance. The hardness and wear specimens were prepared and tested by used Vickers hardness tester and a pin-on-disk wear test apparatus machine at room temperature. The hardness, wear rate, and CoF of TMCs are 476.79 VHN, 13.158 mg/m (×10−3), and 0.955420243, respectively. The results elucidated the microstructure, hardness, wear rate, coefficient of friction, and SEM images of wear for the effects of added reinforcement tungsten carbide.

Effect of Additive Elements (x = Cr, Mn, Zn, Sn) on the Phase Evolution and Thermodynamic Complexity of AlCuSiFe-x High Entropy Alloys Fabricated via Powder Metallurgy

Abstract: In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and spark plasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFe-x (x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSn alloy contained FCC with CuxSny while AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr and AlCuSiFeMn showed the formation of BCC + FCC with additional σ- and µ-phases in the HEA matrix. The calculated thermodynamic parameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mn give rise to major BCC with brittle σ- and µ-phase, which further improves their mechanical strength.

Microstructure and Mechanical Properties of Metal Foams Fabricated via Melt Foaming and Powder Metallurgy Technique: A Review

Abstract: Metal foams possess remarkable properties, such as lightweight, high compressive strength, lower specific weight, high stiffness, and high energy absorption. These properties make them highly desirable for many engineering applications, including lightweight materials, energy-absorption devices for aerospace and automotive industries, etc. For such potential applications, it is essential to understand the mechanical behaviour of these foams. Producing metal foams is a highly challenging task due to the coexistence of solid, liquid, and gaseous phases at different temperatures. Although numerous techniques are available for producing metal foams, fabricating foamed metal still suffers from imperfections and inconsistencies. Thus, a good understanding of various processing techniques and properties of the resulting foams is essential to improve the foam quality. This review discussed the types of metal foams available in the market and their properties, providing an overview of the production techniques involved and the contribution of metal foams to various applications. This review also discussed the challenges in foam fabrications and proposed several solutions to address these problems.

Secondary phases strengthening-toughening effects in the Mo–TiC–La2O3 alloys

Abstract: Mo–TiC–La2O3 molybdenum alloys were strengthened and toughened by the synergistic action of nano-carbide particles and rare earth oxides. In this paper, the Mo–TiC–La2O3 alloy system was prepared by powder metallurgy. The microstructure was characterized by optical, scanning, and transmission electron microscopy. The mechanical properties were tested using the hardness tester and universal tensile testing machine. The grain size of the Mo–TiC–La2O3 alloy is smaller than the Mo–TiC and Mo–La2O3 alloys. The strength and elongation of annealed Mo–TiC–La2O3 alloy are 1291 MPa and 6.6%, respectively. The strength and ductility of the annealed Mo–TiC–La2O3 alloy are higher than the Mo–TiC and Mo–La2O3 alloys. According to the interfacial mismatch between the secondary phases and the matrix, along with oxygen impurities interactions, the mechanisms of strengthening and toughening of the secondary phases in the Mo–TiC–La2O3 alloy were revealed.