Fabrication and Characterization of Bimodal Size Al2O3p Reinforced 7075 Aluminium Matrix Composites

Bimodal sized (Nano and Micron) Al2O3 particle-reinforced 7075Al matrix composites were prepared by a new method called rotary stirring-injection process. The Al2O3 particles were injected into the molten 7075 alloy through the flows of inert argon gas, and the rotary stirring was used simultaneously. The effect of bimodal sized Al2O3 particles reinforcement with average size of 30 – 100 nm, 3 – 5 μm and volume fraction of 1 %, 4 % on microstructure, hardness and tribological properties of 7075 Al-based composite was investigated. Experimental results exhibited fine grains, well-dispersed bimodal sized Al2O3 particles and well-bonded interface between Al2O3 particles and 7075Al matrix. The hardness and wear behavior of the bimodal sized Al2O3p/7075 composites were significantly enhanced, being compared to the 7075Al matrix and the single sized Al2O3p/7075 composites.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.16956</p

The Effect of α-Al(MnCr)Si Dispersoids on Activation Energy and Workability of Al-Mg-Si-Cu Alloys during Hot Deformation

The hot deformation behaviors of homogenized direct-chill (DC) casting 6061 aluminum alloys and Mn/Cr-containing aluminum alloys denoted as WQ1 were studied systematically by uniaxial compression tests at various deformation temperatures and strain rates. Hot deformation behavior of WQ1 alloy was remarkably changed compared to that of 6061 alloy with the presence of α-Al(MnCr)Si dispersoids. The hyperbolic-sine constitutive equation was employed to determine the materials constants and activation energies of both studied alloys. The evolution of the activation energies of two alloys was investigated on a revised Sellars’ constitutive equation. The processing maps and activation energy maps of both alloys were also constructed to reveal deformation stable domains and optimize deformation parameters, respectively. Under the influence of α dispersoids, WQ1 alloy presented a higher activation energy, around 40 kJ/mol greater than 6061 alloy’s at the same deformation conditions. Dynamic recrystallization (DRX) is main dynamic softening mechanism in safe processing domain of 6061 alloy, while dynamic recovery (DRV) was main dynamic softening mechanism in WQ1 alloy due to pinning effect of α-Al(MnCr)Si dispersoids. α dispersoids can not only resist DRX but also increase power required for deformation of WQ1 alloy. The microstructure analysis revealed that the flow instability was attributed to the void formation and intermetallic cracking during hot deformation of both alloys

Ultrasound modulated droplet lasers

We demonstrated the ultrasound modulated droplet lasers, in which the laser intensity from whispering gallery mode (WGM) of oil droplets can be reversibly enhanced up to 20-fold when the ultrasound pressure is beyond a certain threshold. The lasing enhancement was investigated with various ultrasound frequencies and pressures. Furthermore, the ultrasound modulation of the laser output was achieved by controlling the ultrasound pressure, the duty cycle, and the frequency of ultrasound bursts. Its potential application was explored via the study on a human whole blood vessel phantom. A theoretical analysis was also conducted, showing that the laser emission enhancement results from the directional emission from a deformed cavity under ultrasound pressure. Our studies reveal the unique capabilities of ultrasound modulated droplet lasers, which could lead to the development of laser emission-based microscopy for deep tissue imaging with high spatial resolution and detection sensitivity that may overcome the long-standing drawback of traditional fluorescence imaging.Published versio