“…The refined grains restrict the motion of dislocations that hence again contribute to the resistance of the matrix from deformation. 22,24,34 The hardness of the composite samples as a function of TiB 2 reinforcement is shown in Figure 10. Figure 10.Microhardness of the developed samples as a function of TiB 2 reinforcement.…”
Section: Resultsmentioning
confidence: 99%
“…There is also additional literature reported on development of MMCs in the semisolid temperature of the alloy using the semisolid casting route. 22,24,32–34…”
In this research, microstructure and mechanical properties of stir rheocast AA2024/TiB2 metal matrix composite have been investigated. The working temperature was 640℃, which was the selected semisolid temperature that corresponds to 40% of the solid fraction. Two weight percentage, 4 wt%, and 6 wt% of the TiB2 reinforcements were added to the matrix. The field emission scanning electron microscope micrographs of the developed composites showed a uniform distribution of the particles in the case of the 2 wt% and 4 wt% of the reinforcements. However, the particles agglomerated as the weight percentages of the reinforcement increases to 6%. The optical microscope of the liquid cast sample showed the dendritic structure, whereas the rheocast samples showed a globular structure. The X-ray diffraction analysis confirmed the distribution of the reinforcements in the matrix and the formation of some intermetallic compounds. Mechanical properties significantly improved by the addition of the reinforcements in the matrix. An increase in tensile strength of 13.3%, 40%, 28%, and 5% was achieved for the unreinforced rheocast sample, 2 wt%, 4 wt%, and 6 wt% reinforced rheocast samples respectively, compared to the liquid cast sample. An increase in 20% of hardness was attained for the composite with 2 wt% TiB2 compared to the liquid cast sample. According to the fractography analysis, small dimples were observed on the fractured surface of the unreinforced rheocast sample, whereas small and large voids were dominant on the fractured surface of the 2 wt% composite, which shows the ductile fracture mode.
“…The refined grains restrict the motion of dislocations that hence again contribute to the resistance of the matrix from deformation. 22,24,34 The hardness of the composite samples as a function of TiB 2 reinforcement is shown in Figure 10. Figure 10.Microhardness of the developed samples as a function of TiB 2 reinforcement.…”
Section: Resultsmentioning
confidence: 99%
“…There is also additional literature reported on development of MMCs in the semisolid temperature of the alloy using the semisolid casting route. 22,24,32–34…”
In this research, microstructure and mechanical properties of stir rheocast AA2024/TiB2 metal matrix composite have been investigated. The working temperature was 640℃, which was the selected semisolid temperature that corresponds to 40% of the solid fraction. Two weight percentage, 4 wt%, and 6 wt% of the TiB2 reinforcements were added to the matrix. The field emission scanning electron microscope micrographs of the developed composites showed a uniform distribution of the particles in the case of the 2 wt% and 4 wt% of the reinforcements. However, the particles agglomerated as the weight percentages of the reinforcement increases to 6%. The optical microscope of the liquid cast sample showed the dendritic structure, whereas the rheocast samples showed a globular structure. The X-ray diffraction analysis confirmed the distribution of the reinforcements in the matrix and the formation of some intermetallic compounds. Mechanical properties significantly improved by the addition of the reinforcements in the matrix. An increase in tensile strength of 13.3%, 40%, 28%, and 5% was achieved for the unreinforced rheocast sample, 2 wt%, 4 wt%, and 6 wt% reinforced rheocast samples respectively, compared to the liquid cast sample. An increase in 20% of hardness was attained for the composite with 2 wt% TiB2 compared to the liquid cast sample. According to the fractography analysis, small dimples were observed on the fractured surface of the unreinforced rheocast sample, whereas small and large voids were dominant on the fractured surface of the 2 wt% composite, which shows the ductile fracture mode.
“…This method prevents agglomeration and the gravity induced reinforcement segregation by mechanically entrapping the dispersed phase in the semi-solid slurry. Further, the reinforcing particles are better distributed, and gives lower porosity casting [63,64]. The better wettability between the matrix and the dispersed phase, and matrix alloy lower volume shrinkage are accountable for the lower porosity.…”
This chapter discusses the concepts, casting techniques and applications of functionally graded materials metal matrix composites (FGMMCs). Considerations were given to bulk functionally graded aluminium matrix composites (FGAACs) production processes. Liquid-metal forging processes of FGAACs fabrication, such as infiltration process, squeeze casting, friction casting or compocasting, stir, and centrifugal casting were discussed. The chapter provides basic concepts of the processes and overview of their processing parameters, such as mould rotational speed; reinforcement particles size and volume; degassing method; melting and pouring temperatures; pressure; and stirrer. The study notes that functionally graded materials (FGMs) are commonly used in automotive, aircraft, aviation, chemical, medical, engineering, renewable energy, nuclear energy, and optics electronics industries.
“…As a result, the particles sink or float depending on their relative density to the liquid matrix density, causing a non-uniform reinforcement distribution. Therefore, due to poor particle dispersion, agglomeration occurs, which leads to the formation of high porosity content in the composite [5,6]. There are several methods reported to improve the wettability between the particle and matrix.…”
Section: Introductionmentioning
confidence: 99%
“…Some of them are the addition of wetting agents [7] and fluxes [8], oxidation [9], preheating [10], and coating [11] of the particles. Another cost-effective method reported for improving wettability is to develop the composite in the semi-solid temperature region of the alloy [4][5][6][12][13][14]. The developed alternative method is called semi-solid metal (SSM) casting/compocasting/stir rheocasting.…”
AA2024 reinforced with varying amounts of titanium boride (TiB 2) was developed using stir rheocasting to study the effect of solution heat treatment on aging behavior and mechanical properties. The developed specimens were subjected to solution heat treatment at 490 °C for 1, 2.5, and 5 h, followed by artificial aging at 190 °C for an aging duration of 1-12 h. The metallurgical characterization was done by x-ray diffraction, optical microscopy, and field emission scanning electron microscope and mechanical characterization by Vickers hardness tester and universal testing machine. Microstructural observation showed the formation of globular grains and fairly uniform particle distribution. Up on peak aging, the AA2024/2 wt% TiB 2 composite has shown better improvement in yield strength (YS = 230 MPa), tensile strength (UTS = 342 MPa), and Vickers hardness (VH = 147) amongst other developed specimens. The improvement in mechanical properties of AA2024/2 wt% TiB 2 composite up on peak aging was nearly 83%, 77%, and 20%, respectively, over their as-cast states. However, the percent elongation has decreased by 51% for the AA2024/2 wt% TiB 2 composite against its as-cast state. The optimum solution heat treatment time was found to be 2.5 h that led to the fastest aging kinetics and peak hardness. Due to incomplete dissolution of precipitates at a solution treating time less than 2.5 h, the hardness decreased, and the aging kinetics decelerated. The aging kinetics further accelerated with increasing solution heat treating time beyond 2.5 h, but the hardness decreased due to grain growth of the matrix.
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