Search

Strength and wear properties of metal matrix composites are important because of their numerous applications in automotive and aerospace industries. In the present study, Al-Cu alloy-based nanocomposites reinforced with different volume percentages of Al2O3 particles were developed by reactive stir mixing of nanocrystalline CuO powder in molten Al. X-ray diffraction (XRD) patterns of the resulting nanocomposites revealed the presence of Al2O3 reinforcements and CuAl2 intermetallic particles. Microstructural characteristics of the samples were investigated and analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM analysis revealed the presence of geometrically necessary dislocations and microcracks inside the sample. Average dislocation density was determined by the modified Warren–Averbach method from XRD patterns. The near-surface wear behavior of the composites was studied by nanoscratch tests. The results were correlated with the microstructural features and dislocation density. [ABSTRACT FROM AUTHOR]

Anodic alumina films with uniformly distributed self assembled pores of diameters in the nanometric length scale were prepared by dual step anodization technique in oxalic, phosphoric and sulphuric acid medium. The variations of pore morphology and photoluminescent properties were studied with respect to the change in electrolytic medium. The photoluminescence (PL) spectra of the films prepared in different electrolytic medium have been recorded and compared. The PL spectra of the porous anodic alumina (PAA) film prepared in oxalic acid was found to be much stronger than the PAA prepared in phosphoric and sulphuric acid. However, pore size of the PAA films prepared in oxalic and sulphuric acid were significantly smaller than the PAA films prepared in phosphoric acid medium. Presence of oxygen deficient defect centre exerts a strong influence on the PL properties of the films. [ABSTRACT FROM AUTHOR]

In this investigation, wear and tensile properties of 6061-Al/Al2O3 and 6061-Al/SiC metal matrix composites were studied with respect to their microstructural features and residual stresses. Variation in the residual stress values in the composites differed from each other due to their particulate size and thermal expansion coefficient. Tribological behavior of the composites studied with the aid of nanoscratch tester showed higher amount of debris in 6061-Al/SiC composite than that in 6061-Al/Al2O3 composite due to the presence of higher residual stresses and shorter interparticle distance in the former. Variation of wear volume, coefficient of friction and wear rate at different load were analyzed and correlated with the variation of microstructure along the scratch tracks. It is seen that wear resistance of 6061-Al/Al2O3 is better than that of 6061-Al/SiC composite, where as tensile property revealed that ultimate tensile stress and yield stress is higher in case of 6061-Al/SiC composite compared to 6061-Al/Al2O3. Fractographic studies shows bimodal fracture failure where cleavage type brittle fracture failure is dominant in 6061-Al/Al2O3 whilst ductile failure is dominant in 6061-Al/SiC composite. [ABSTRACT FROM AUTHOR]