Sharif Digital Repository

Due to their favorable biodegradability, Magnesium and its alloys have always attracted such a lot of research interests for making temporary implants. With the same direction, Mg-4Zn-0.2Ca has recently absorbed lots of research interests, due to its excellent biocompatibility. As the most regarded draw back concerned with this alloy, poor corrosion resistance is frequently discussed. Accordingly, in the present work it has been tried to come over this problem by addition different amount of aluminum, including 1, 3, 5, 7.5, and 10 percent, to this alloy; without causing any negative effect on its biocompatibility, and to present a new alloy composition with modified degradation behavior.... 

In this study, Cu-TiC nanocomposites were produced by high energy ball milling of elemental powders and in situ formation of TiC in the copper base. Cu and 5,10,20 and 40 wt% Ti powder blend were milled for 60 h, then graphite powders were added and milling was continued for 10 h again and Finally Cu-TiC composite powders with 10.68, 20.16, 36.24 and 60.25 vol% of reinforcements (6.18, 12.2, 23.82 and 45.47 wt%) were produced. The effect of time on the solution of titanium in the copper was studied by X-Ray diffraction analysis (XRD). crystallite size and lattice strain of copper were determined 12nm and 1.04% subsequently for Cu-40wt%TiC after 60 h milling. to ensure the formation of... 

In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti Powder mixtures. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a vibratory mill up to 7 hr. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with... 

In this project formation of MgO & Mg2Cu reinforcement particle in Magnesium matrix was investigated. Firstly Mg & CuO powders mixture in different weight percentage (4, 8%wt CuO) in 20:1 and 30:1 BPR were milled. Finally, according to XRD result 30:1 BPR was selected for milling. Variations in powders morphology, particles size, crystallite size, lattice strain and phase transformation were investigated by X-ray diffraction, scanning electron microscopy and laser particle size analyzer in different milling time. Result showed that during reaction between Mg and CuO, MgO & Mg2Cu reinforcement particles were formed in matrix. Matrix crystallite size was determined about 35-40 nm. Mg-6.3%wt Cu... 

Due to the ability in producing nanostructured materials, Mechanical Alloying has gained outstanding position in comparison with other materials fabrication techniques. In this research,with different milling condition, Alloying of Ni-Ti-Ag was performed. In order tofabricating the alloy, twodifferent initial materials were employed.In one process, nickel, titanium and silver were used as raw materials, and in another, titanium hydride was used instead of titanium.Initial powders were investigated in planetary mill, SPEX mill and vibratory disc indifferent times. Using XRD, microstructure information and phase analysis was obtained. EDS was employed for determination of elemental... 

In this research, nano composite MgH2-TiCr1.2 Fe0.6 nano crystalline was synthesized by mechanical alloying and Vacuum arc re-melting (VAR). the effect of Milling conditions and adding nano crystalline TiCr1.2 Fe0.6 as a catalyst on the structure and hydrogen desorption properties of MgH2 were studied. MgH2 powder grain size after 4 hours milling gained to 15nm and strain network reached to 0.8%. Determined that the increasing of accumulated lattice strain because of mechanical milling combined with adding nano crystalline alloy TiCr1.2 Fe0.6 significantly improve the properties of MgH2 hydrogen desorption. After an hour mill working, high pressure phase of γ-MgH2 was appeared in... 

In this study in-situ Al/Al3Ti was fabricated by mechanical alloying, hot extrusion and subsequent heat treatment. First, initial pure powders of Al and Ti were mechanically alloyed with 5 weight percentages of Ti for 40 hours. The as-hot extruded samples containing 5 wt% of initial Ti particles, were exposed to heating at 600 oC for various time intervals up to 10 hours. Microstructure analysis by OM and SEM proved that in-situ Al3Ti phase was formed as a layer around Ti particles by solid reactive diffusion between Al and Ti particles. After 10 hours of heating, all the Ti particles were consumed and transformed to Al3Ti. Mechanical properties of samples were investigated by Brinell... 

In the present investigation, the mechanical alloying (MA) technique was employed to produce nanocrystalline Al-Ti alloys. Elemental Al and Ti powders were mixed with different compositions (0, 5, 10, and 20 wt.% Ti) and then, milled in a planetary ball-mill up to 40 h. The variations of powder morphology and particle size, apparent and tap densities, microstructure, grain size, lattice strain, and microhardness were studied with increasing the milling time. While dissolution of Ti in the Al matrix resulted to the formation of supersaturated Al-Ti solid solution in the samples containing 5 and 10 wt.% Ti, the specimen with 20 wt.% Ti, eventually, led to nanocomposite powder with different... 

Al /Al3Ti in-situ composite have been fabricated by mechanical alloying and two-step hot pressing of powders containing Al and 20%wt Ti. Samples were characterized by using optical microscopy, density measurement, brinel hardness, XRD analysis. An increasing density was observed with increasing pressure until certain pressure and after that the density of composite decreased, which can be attributed to the increase in the level of porosity level and the amount of forming Al3Ti. The samples that hot pressed under cycle 5 and 6, showed the most volume fraction of in-situ phases on the matrix. The wear behavior of Al based composites reinforced with in situ Al3Ti particles has been investigated... 

Nickel aluminides are intermetalics with complex structures that have high metlting points. However, brittlement at room temperature and low high_temperature strength (above 700 ̊C) can be mentioned as their short comings. Nowadays, many efforts have been proceeded to produce theirs composites, so that one can benefit from ceramics and intermettalics properties simultaneously. In this project, the main was aim to produce NiAl matrix nanocomposite reinforced with Alumina Al2O3. The composite is processed using milling and mechanical alloying. This is a good way to produce intermetallics and their composites with high melting points without any need to supply high temperature during...