Crystallization and Corrosion Resistance of (Fe_(0.78)Si_(0.09)B_(0.13))100_(-x)Ni_x (x=0,2 and 5) Glassy Alloys

The crystallization of the （Fe0.78Si0.09B0.13）100-xNix glassy alloys （x=O, 2 and 5） has been investigated by X-ray diffraction （XRD） and differential scanning calorimeter （DSC）. Corrosion resistance analyses have been carried out using electrochemical measurements and corrosion products have been analyzed by scanning electron microscopy （SEM）. The experimental results show that the addition of Ni can promote the nucleation of c^-Fe, retard the decomposition of the metastable borides, and alter the crystallization mode of the present Fe-based glassy alloys. The lattice constant （ao^e） of c^-Fe in the annealed samples shows a decreasing trend with increasing annealing time. The Ni addition can improve the corrosion resistance of the as-quenched Fe-based glassy alloys in H2S04, NaCI and NaOH solutions. The results indicate that Ni can promote the diffusion of Si atoms during quenching and annealing processes.

Enhanced wetting and properties of carbon/carbon-Cu composites with Cr_3C_2 coatings by Cr-solution immersion method

A facile ammonium-dichromate solution immersion method was introduced to synthesize the copperwettable Cr3C2 coating on and inside the carbon-carbon （C/C） preform. The formation mechanism and the microstructures of the Cr3C2 coatings were studied. The contact angle between molten copper and the C/C decreased from 140°to 60°, demonstrating the significant improvement in the wettability. The Cr3C2- coated C/C-Cu composite with only 4.2% porosity and 3.69 gcm^-3 density was manufactured through copper infiltration. As a result, the thermal and electrical conductivity of the modified C/C-Cu increased significantly due to the infiltrated copper. Also the mechanical properties of the composites including both the flexural and compressive strengths were enhanced by over 100%. The modified C/C-Cu composite exhibited lower friction coefficients and wear rates for different load levels than those of the commercial C/Cu composite. These results demonstrate the potential of the modified C/C-Cu material for use in electrical contacts.

Effect of Compression on the Crystallization Behavior and Corrosion Resistance of Al_(86)Ni_9La_5 Amorphous Alloy

The effect of compression on the crystallization behavior and corrosion resistance of Al（86）Ni9La5 amorphous ribbons was investigated by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning elec-tron microscopy （SEM） and electrochemistry test. The XRD and TEM results reveal that the compressed Al（86）Ni9La5 ribbons spun with the circumferential speed （R） of 29.3 m/s are in fully amorphous state; however, the compressed ribbons spun with R=14.7 m/s have crystalline phases embedded in the amorphous matrix. The SEM images indicate that after compression, the toughness of the ribbons increases. Electrochemical results show that the compression decreases the stability of the passive film of the Al（86）Ni9La5 amorphous ribbons, because of the compression-introduced free volume, shear bands and crystalline phases; meanwhile, with R=14.7 m/s, the compression-induced crystalline phases in the Al（86）Ni9La5 ribbons increase the corrosion potential.