Processing of Aluminum-Graphite Particulate Metal Matrix Composites by Advanced Shear Technology

Abstract

To extend the possibilities of using aluminum/graphite composites as structural materials, a novel process is developed. The conventional methods often produce agglomerated structures exhibiting lower strength and ductility. To overcome the cohesive force of the agglomerates, a melt conditioned high-pressure die casting (MC-HPDC) process innovatively adapts the well-established, high-shear dispersive mixing action of a twin screw mechanism. The distribution of particles and properties of composites are quantitatively evaluated. The adopted rheo process significantly improved the distribution of the reinforcement in the matrix with a strong interfacial bond between the two. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (e) is obtained compared with composites produced by conventional processes.

Development of Al-B-C Master Alloy Under External Fields

“…A lack of hydrodynamic forces due to a variation in the velocity gradients could result in accumulation of the aggregates in relatively stagnant zones where they survive the shear forces of mixing. [14] These agglomerates are not transported back into the high-shear regions and finally find their way as clusters into the cast structures. Thus mixing is limited for the clusters located away from the impeller, resulting in the characteristic microstructure as shown in Figure 2(3).…”

“…The conventional mechanical stirring was used for distributive mixing [12][13][14] to pre-mix the graphite particles with the Al-B melt. The mixing equipment as shown in Figure 1 consisted of a driving motor to create the torque on the impeller, a lifting mechanism for the rotation drive unit and stirrer assembly, and a transfer tube for introducing the graphite powder into the melt.…”

Influences of graphite reinforcement on the tribological properties of self-lubricating aluminum matrix composites for green tribology, sustainability, and energy efficiency—a review

“…Graphite particles act as solid lubricant at the contact interface, which enhance the tribological properties of these composites compared to unreinforced aluminum alloys or aluminum alloys reinforced by non-carbonous ceramic particles [32,82,83]. In general, solid lubricants to fabricate self-lubricating composites are solid carbon (carbon fibers [84][85][86], graphite particles [87][88][89][90][91], CNTs, graphene), molybdenum disulfide, and hexagonal boron nitride [2, 16,81]. Low friction coefficient and low wear rate are the key properties of self-lubricating materials as well as their high seizure resistance.…”

“…Casting method usually involves producing a melt of the base alloy, introducing solid lubricating particles in the melt, casting the slurry, followed by further heat treatment, if necessary. Two common casting methods used to synthesize the nonequilibrium synthetic type of self-lubricating aluminum matrix composites are (a) infiltration technique, impregnation of the liquid alloy into a graphite preform under high pressure (70-100 MPa), such as squeeze casting and pressure infiltration [44,92,102,105] and (b) dispersion method, such as stir casting or compo-casting in liquid or semi-solid state [80,91,103,106,107]. In pressure infiltration, a loose bed of graphite powder or a bonded perform of graphite is infiltrated by molten alloys, which is then allowed to solidify; the pressure infiltration is suitable for metal graphite composites with very high volume percentage of graphite.…”

Influence of Activated Carbon Particles on Microstructure and Thermal Analysis of Aa7075 Metal Matrix Composites

“…Aluminium carbon particulate MMCs made by natural action techniques represent a category of cheap customized materials for a spread of engineering applications. [13][14][15] It is accustomed create elements requiring tensile, and good wear resistance like aerospace and automotive vehicles parts. [16][17][18] This has attended to enhanced analysis interest for appraising the result of the kind of weight fraction of reinforcement within the matrix and for various different procedures that area unit accustomed manufacture of MMCs.…”