Cryogenic Drilling of AZ31 Magnesium Syntactic Foams

Abstract

Machined surface quality and integrity affect the corrosion performance of AZ31 magnesium composites. These novel materials are preferred for temporary orthopedic and vascular implants. In this paper, the drilling performance of AZ31-magnesium reinforced with hollow alumina microsphere syntactic foam under LN2 cryogenic, dry, and Almag® Oil is presented. Cutting tests were conducted using TiAlN physical vapor deposition (PVD) coated multilayer carbide and K10 uncoated carbide twist drills. AZ31 magnesium matrices were reinforced with hollow alumina ceramic microspheres with varying volume fractions (5%, 10%, 15%) and average bubble sizes. Experimental results showed that the drilling thrust forces increased by 250% with increasing feed rate (0.05 to 0.6 mm/tooth) and 46% with the increasing volume fraction of alumina microspheres (5% to 15%). Cryogenic machining generated 45% higher thrust forces compared to dry and wet machining. The higher the volume fraction and the finer the average size of hollow microspheres, the higher were the thrust forces. Cryogenic machining (0.42 µm) produced a 75% improvement in surface roughness (Ra) values compared to wet machining (1.84 µm) with minimal subsurface machining-induced defects. Surface quality deteriorated by 129% with an increasing volume fraction of alumina microspheres (0.61 µm to 1.4 µm). Burr height reduction of 53% was achieved with cryogenic machining (60 µm) compared to dry machining (130 µm). Overall, compared to dry and wet machining methods, cryogenic drilling can be employed for the machining of AZ31 magnesium syntactic foams to achieve good surface quality and integrity.

Estimation of cutting forces in CNC slot-milling of low-cost clay reinforced syntactic metal foams by artificial neural network modeling

“…Bolat et al (2022) conducted machining work on the pumice-reinforced foams and concluded that cutting force values diminished depending on the increasing cutting speeds due to the thermal softening of the matrix and the fragile nature of SiO 2 -based particles. Kannan et al (2020b) tended to cryogenic machining of the AZ31 syntactic foams and enounced that better surfaces could be achieved through low-temperature cutting. The same team offered a mechanistic model to MMMS 20,3 explicate the load/deformation transfer between AZ91 foam constituents (Kannan et al, 2021).…”

An experimental examination of the dry drilling machinability features of cellular glass‐filled new‐generation metallic composite foams

“…Even though this investigation revealed the effect of the filler particle size on the machining force of the metallic foams, utilized bubble alumina spheres can be interpreted as expensive compared to other alternative fillers. On the other side, cryogenic machining applications have been popular among investigators and this approach has been applied to the alumina-filled magnesium composite foams to obtain the better surface quality of the machined parts [23]. In addition to these findings, cryogenic machining leads to thrust force increasing that influences tool life negatively although it helps attain lower surface roughness values on the machined surfaces.…”