Effects of infiltration pressure on mechanical properties of Al–12Si/graphite composites for piston engines

Abstract

In this work results for the flexural strength and the thermal properties of interpenetrated graphite preforms infiltrated with Al-12wt%Si are discussed and compared to those for packed graphite particles. To make this comparison relevant, graphite particles of four sizes in the range 15-124 µm, were obtained by grinding the graphite preform. Effects of the pressure applied to infiltrate the liquid alloy on composite properties were investigated. In spite of the largely different reinforcement volume fractions (90% in volume in the preform and around 50% in particle compacts) most properties are similar. Only the Coefficient of Thermal Expansion is 50% smaller in the preform composites. Thermal conductivity of the preform composites (slightly below 100 W/m.K), may be increased by reducing the graphite content, alloying, or increasing the infiltration pressure. The strength of particle composites follows Griffith criterion if the defect size is identified with the particle diameter. On the other hand, the composites strength remains increasing up to unusually high values of the infiltration pressure. This is consistent with the drainage curves measured in this work. Mg and Ti additions are those that produce the most significant improvements in performance. Although extensive development work remains to be done, it may be concluded that both mechanical and thermal properties make these materials suitable for the fabrication of piston engines.

Investigation of Production and Mechanical Properties of Hybrid Particle Reinforced Al-Metal Matrix Composites

“…That is to say the pore dividers are themselves fired composites which can consolidate both properties as fortification. .Similar results are also reported [9].…”

Effect of Al–Mg Alloy Infiltration on Mechanical and Electrical Properties for Carbon/Carbon Composites

“…Figure 10e illustrates the phenomenon of the Al-Mg alloy surrounding pyrolytic carbon. This result can be attributed to the good wettability observed between Al and pyrolytic carbon [37]. For C/C-Al-Mg composites with carbides at the interface, the formation of carbides consumed the C element of carbon fibers, transforming interfacial bonding into …”

A Critical Review on Synthesis of Aluminum Metallic Composites through Stir Casting: Challenges and Opportunities

“…[22,118] Pressure Infiltration: In this technique, the pressure is created directly or through other external means such as through vacuum, squeeze action, centrifugal force, inert gas, vapor, and so on. [137,138] This technique is mainly adopted while dealing with a higher concentration of reinforcement in which a molten matrix is required to solidified. [36,139] The major stages involved in this production method are shown in Figure 8.…”

“…Blucher [140] reported a pressure infiltration technique as an economical fabrication method with the exceptional property as it is not affected by the wettability between the constituents. Narciso et al [137] adopted a pressure infiltration technique to fabricate the Al-12Si/Gr p composites and reported enhanced mechanical as well as thermal properties suitable for the development of the automotive pistons. Yang et al [138] fabricated Al/GNPs composites through pressure infiltration and noted excellent ultimate tensile strength (UTS) and yield strength (YS) without any formation of aluminum carbides.…”