On the Role of Hollow Aluminium Oxide Microballoons during Machining of AZ31 Magnesium Syntactic Foam

Abstract

The role played by hollow ceramic thin-walled aluminium oxide microballoons on the shear deformation characteristics of AZ31 Magnesium syntactic foam is studied through high-speed machining. The ceramic microballoons embedded in the AZ31 matrix provides the necessary stiffness for these novel foams. The effect of hollow ceramic microballoon properties, such as the volume fraction, thin wall thickness to diameter ratio, and microballoon diameter, profoundly affects the chip formation. A novel force model has been proposed to explain the causes of variation in cutting forces during chip formation. The results showed an increase in machining forces during cutting AZ31 foams dispersed with higher volume fraction and finer microballoons. At a lower (Davg/h) ratio, the mode of microballoon deformation was a combination of bubble burst and fracture through an effective load transfer mechanism with the plastic AZ31 Mg matrix. The developed force model explained the key role played by AZ31 matrix/alumina microballoon on tool surface friction and showed a better agreement with measured machining forces.

Cryogenic Drilling of AZ31 Magnesium Syntactic Foams

“…Magnesium syntactic foam billets were manufactured through the squeeze casting method [11]. During the casting process, the stirrer RPM was maintained between 450-500 RPM for 10 min.…”

“…It has been shown that an increase in the volume fraction of hollow microspheres increases the hardness, compression yield strength, peak compression strength, and plateau strength of the syntactic metal foams [7][8][9][10]. The coarser the average size of hollow reinforcements is, the lower the hardness of the magnesium closed-cell foam [11,12]. The mechanical properties of aluminum-based syntactic foam are shown to be comparable to the base alloy under cryogenic conditions [8].…”

“…Not many studies have been carried out to study the machined surface quality and integrity of AZ31 magnesium matrix syntactic foams and hence the focus of this research. Syntactic foam materials are classified as difficult-to-cut due to its heterogeneous microstructure and inherent brittleness of the reinforcing hollow ceramic microsphere phase [11]. Machining of magnesium-based syntactic foam presents significant challenges in the form of dimensional accuracy due to edge delamination and disintegration.…”

Carbon Fiber Reinforced Multi-Phase Epoxy Syntactic Foam (CFR-Epoxy-Hardener/HGMS/Aerogel-R-Hollow Epoxy Macrosphere(AR-HEMS))

“…These reinforced materials have a relatively large density, which is not conducive to providing large buoyancy for deep-sea exploration equipment [ 10 , 11 ]. The introduction of the low-density aerogel is more conducive to reducing the density of foam to improve the overall performance and reduce the energy consumption of the submersible [ 12 , 13 , 14 ]. In this experiment, the aerogel reinforced hollow epoxy macro-spheres (AR-HEMS) was prepared innovatively by ‘the rolling ball method,’ and the same rolling time and method were adopted to make the aerogel powder wrapped around the EPS beads evenly [ 15 , 16 ].…”

Transient Thermomechanical Simulation of 7075 Aluminum Contraction around a SiO2 Microparticle

“…Oxide particles, such as Al 2 MgO 4 , Al 2 O 3 , MgO, and SiO 2 , observed in aluminum alloys are extremely hard concerning the matrix and their treatment represent a complex technological challenge [ 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. The addition of microparticles in metals, combined with proper thermomechanical treatment, can be used to increase the mechanical properties in a beneficial sense [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”