Mechanical and wear properties of Al-Al_3Mg_2 nanocomposites prepared by mechanical milling and hot pressing

β-A13Mg2 intermetallic was used as a reinforcing agent to improve the mechanical properties of an aluminum matrix. Different amounts of A13Mg2 nanoparticles （ranging from 0wt% to 20wt%） were milled with aluminum powders in a planetary ball mill for 10 h. Consolidation was conducted by uniaxial pressing at 400β under a pressure of 600 MPa for 2 h. Microstructural characterization confirms the uniform distribution of A13Mg2 nanoparticles within the matrix. The effects of nano-sized A13Mg2 content on the wear and mechanical properties of the composites were also investigated. The results show that as the A13Mg2 content increases to higher levels, the hardness, compressive strength, and wear resistance of the nanocomposites increase significantly, whereas the relative density and ductility decrease. Scanning electron microscopy （SEM） analysis of worn surfaces reveals that a transition in wear mechanisms occurs from delamination to abrasive wear by the addition of A13Mg2 nanoparticles to the matrix.

Structural characterization of AA 2024-MoSi_2 nanocomposite powders produced by mechanical milling

Nano-sized MoSi2 powder was produced successfully from commercially available MoSi2 by a mechanical milling process carried out for 100 h, and mechanical alloying was employed to synthesize AA 2024-MoSi2 nanocomposites, The effects of MoSi2 reinforcement and mechanical milling on the structure, morphology, and iron contamination of the produced materials were investigated using X-ray diffraction, scanning electron microscopy, and atomic absorption spectrometry. It is revealed that the morphology of the aluminum alloy changes continuously during milling from spherical to plate-like, irregular, and finally equiaxed. The presence of MoSi2 reinforcement accelerates the milling process and results in a smaller average particle size. The Williamson-Hall method determined that the crystallite size of the aluminum alloy in the composite powder is smaller than that of the unreinforced alloy at the same milling time and this size reaches 45 nm after 16 h milling time. The Fe contamination content is higher for the nanocomposite in comparison with the unreinforced alloy because of the wearing role of MoSi2 hard particles.

Synthesis and Characterization of Indium Niobium Oxide Thin Films via Sol—Gel Spin Coating Method

In the present study, niobium-doped indium oxide thin films were prepared by sol-gel spin coating technique. The effects of different Nb-doping contents on structural, morphological, optical, and electrical properties of the films were characterized by means of X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM）, atomic force microscopy （AFM）, UV-Vis spectroscopy, and four point probe methods. XRD analysis confirmed the formation of cubic bixbyite structure of In203 with a small shift in major peak position toward lower angles with addition of Nb. FESEM micrographs show that grain size decreased with increasing the Nb-doping content. Optical and electrical studies revealed that optimum opto-electronic properties, including minimum electrical resistivity of 119.4 × 10^-3 Ω cm and an average optical transmittance of 85% in the visible region with a band gap of 3.37 eV were achieved for the films doped with Nb-doping content of 3 at.%. AFM studies show that addition of Nb at optimum content leads to the formation of compact films with smooth surface and less average roughness compared with the prepared ln2O3 films.

Microstructural characteristics and second-phase particles in yttrium-bearing Fe-10Ni-7Mn martensitic steels

In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing Fe-10Ni-7Mn steels were characterized. The results of X-ray analysis as well as scanning electron microscopy coupled with energy dispersive X-ray spectroscopy indicated the formation of （Fe, Ni, Mn）17Y2 precipitates with hexagonal structure in a Fe-10Ni-7Mn-0.8Y （wt.%） alloy. Lattice parameters of these precipitates were calculated as follows：a=0.8485 nm and c=0.8274 nm. Formation of Y2O3 sub-micron particles was also confirmed in both yttrium bearing steels via electrolytic phase extraction method. The effect of these precipitates on the prior austenite grain size was investigated. The results revealed that these precipitates had an effective role in controlling the prior austenite grain size.