Processing, microstructure and mechanical properties of micro-SiC particles reinforced magnesium matrix composites fabricated by stir casting assisted by ultrasonic treatment processing

Influence of ultrasonication power on grain refinement, mechanical properties and wear behaviour of AZ91D/nano-Al2O3 composites

“…UST effectively distributed the nanoparticles which improved the density and porosity. The high intensified UST promoted degassing effect in magnesium melt during the casting which further reduced the porosity [7]. Moreover, the squeeze pressure imposed during the freezing process caused a substantial reduction in the microporosity in the composites [36].…”

“…This is attributed to the absence of UST during casting. During the mechanical stirring, the nanoparticles tend to form clusters due to agglomeration [7]. clusters broken into tiny clusters due to the impact of high-intensified ultrasonic vibration [14].…”

“…Alternate cycles of ultrasonic vibration caused the instantaneous breakdown in the cavitation bubbles; creating high temperature and pressure spots in the composite melt. This high temperature and pressure spots produced large energy in the melt which enhances the wettability between nanoparticles and the matrix [7,29]. Therefore, most n-Al 2 O 3 particles in the melt became active and formed nuclei in the solidification process leading to easy heterogeneous nucleation upon a slight undercooling [26,29].…”

“…Also, long stirring time causes oxidation to the magnesium matrix often resulting in poor quality casting. Reduction in the stirring time is necessary to ensure the improvement of the quality of the casting [7]. Besides, the higher surface to volume ratio and poor wettability of nanoparticles cause agglomeration which leads to deteriorated grain structure.…”

Microstructure and Wear Behavior of B4C Particulates Reinforced Al-4.5%Cu Alloy Composites

“…Metal matrix composites are capable of providing higher temperature operating limits than their base metal counterparts, and can be tailored to give improved strength, stiffness, thermal conductivity, abrasion resistance, creep resistance or dimensional stability [1][2]. Unlike resin matrix composites, MMCs are nonflammable, do not outgas in a vacuum and suffer minimal attack by organic fluids such as fuels and solvents.…”