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The present investigation deals with development of AA2219 composites with different weight fractions of Cerium oxide (CeO2) reinforcement and characterizing the microstructure and mechanical properties thereof. XRD and SEM micrograph confirm the presence of CeO2 particles and Al2Cu precipitate. The grain size of 0, 0.5, 1.0, 1.5 and 2 wt% CeO2 composites are 483, 453, 411, 362 and 328 μm, respectively. Addition of CeO2 significantly reduces the dendritic morphology and refines the α-Al grain structure. 2 wt% CeO2 addition has yielded the maximum hardness of 124 HV and yield strength of 87 MPa in all the composites developed. Additionally, the developed composites were evaluated by examining the wear characteristics with the co-efficient of friction (COF) and the specific wear rate. In this study, Taguchi's L25 orthogonal array was used to optimize the parameters like reinforcement fraction, load and sliding distance. Signal-to-noise ratio (S/N ratio) and analysis of variance (ANOVA) are used to obtain the parameters highly influencing the wear behaviour. Adhesive wear is exhibited by ploughing at lower loads and delamination is observed with increasing load. Deep shallow ploughs with embarked abrasion are observed at higher loads.

Nanocrystalline powders of 4 mol.% GdO1.5-4 mol.% SmO1.5 doped ZrO2 (4Gd4SmSZ) has been synthesized by co-precipitation process. Their phase transformation and crystalline growth behavior was investigated by Thermo gravimetric-Differential Thermal Analysis (TG-DTA), X-ray Diffraction (XRD), Raman spectroscopy and High-Resolution Transmission Electron Microscopy (HR-TEM) after calcinations at different temperatures. The XRD, Raman spectra and HRTEM results confirm the nature of tetragonal zirconia (t-ZrO2). The prepared 4Gd4SmSZ powders, remains in the single metastable tetragonal phase over the whole calcination temperature ranging from 873 K to 1273 K for 2 h. The crystallite size varies from 11.98 nm to 18.90 nm with increase of temperature from 873 K to 1273 K. The activation energy of the prepared powders at low temperature is considerably lesser than that at a higher temperature. The annealed 4Gd4SmSZ powders had shown excellent phase stability at 1573 K for 100 h. Keywords: Zirconia, Coprecipitation, Rare earth oxide, Phase transformation, Tetragonal, Activation energy