Iranian Journal of Materials science and Engineering
Volume:14 Issue: 1, Mar 2017

In the present work, one batch of prealloyed 6061Al powder was processed by mixing and another one was ball milled with varying amount of lead content (0-15 vol. %). These powders were compacted at 300MPa and sintered at 590˚C under N2. The instrumented hardness and the young’s modulus of as-sintered 6061Al-Pb alloys were examined as a function of lead content and processing route. The wear test under dry sliding condition has been performed at varying loads (10-40 N) using pin-on-disc tribometer. The microstructure and worn surfaces have been investigated using SEM to evaluate the change in topographical features due to mechanical alloying and lead content. The mechanically alloyed materials showed improved wear characteristics as compared to as-mixed counterpart alloys. Delamination of 6061Al-Pb alloys decreases up to an optimum lead composition in both as-mixed and ball-milled 6061Al-Pb alloys. The results indicated minimum wear rate for as-mixed and ball-milled 6061Al alloy at 5 and 10 vol. % Pb, respectively.

The synthesis of micro-sized, uniformly distributed Al2O3-15Vol% Ni powders were studied through three step co-precipitation of hydroxides mixtures from proper solution, calcination at air atmosphere and final step of calcined powders in a carbon bed. Al and Ni hydroxide and amorphous phase were first obtained from their salt’s solutions through chemical co-precipitation method by adjusting pH. The precipitated powders were then calcined to obtain a mixture of their oxides as NiO and NiAl2O4 which were reduced in a carbon bed at various temperatures up to 1300. Proper temperature for calcination in air was determined through TG analysis; 900. SEM observation of powders after reduction, revealed micro-sized Ni particles, along with fin distribution of Ni and Al2O3 elements. XRD analysis of the calcined sample showed the presence of NiAl2O4 and NiO and the same analysis for the reduced sample confirmed the formation of Al2O3 and Ni.

In this paper the feasibility of fabricating controlled porous skeleton of pure tungsten at low temperature by addition of submicron particles to tungsten powder (surface activated sintering) has been studied and the best parameters for subsequent infiltration of Cu were acquired. The effects of addition of submicron particles and sintering temperature on porous as well as infiltrated samples were studied. The samples were examined by scanning electron microscopy (SEM), Vickers hardness measurements and tensile test. The composites made have been investigated and revealed the making W-Cu composite with good density, penetrability, hardness and microstructure. Consequently, the sintering temperature was reduced considerably (Ts≤1650oC) and a homogeneous porous tungsten was obtained. Also, composite prepared by this method exhibited elongation about 28% that is much more than conventional W-15%wt Cu composites. This method of production for W–Cu composites has not been reported elsewhere.

In this work, the effects of co-precipitation temperature and post calcination on the magnetic properties and photocatalytic activities of ZnFe2O4 nanoparticles were investigated. The structure, magnetic and optical properties of zinc ferrite nanoparticles were characterized by X-ray diffraction (XRD), vibrating sample magnetometry and UV–Vis spectrophotometry techniques. The XRD results showed that the coprecipitated as well as calcined nanoparticles are single phase with partially inverse spinel structures. The magnetization and band gap decreased with the increasing of co-precipitation temperature through the increasing of the crystallite size. However, the post calcination at 500 °C was more effective on the decreasing of magnetization and band gap. Furthermore, photocatalytic activity of zinc ferrite nanoparticles was studied by the degradation of methyl orange under UV-light irradiation. Compare with the coprecipitated ZnFe2O4 nanoparticles with 5% degradation of methyl orange after 5 h UV-light light radiation, the calcined ZnFe2O4 nanoparticles exhibited a better photocatalytic activity with 20% degradation.

The boronizing of a tungsten heavy alloy containing Ni and Fe as the major alloying elements were performed in the present study to increase its surface hardening. Pack cementation method was employed as a well-known, successful solid-state process for boronizing. The coating treatment was accomplished at different temperatures of 1000, 1050 and 1100°C for 6 and 9 hours. The formation of tungsten boride phase was confirmed, although a silicide layer covered the surface of the specimen as the outer layer. The mechanism of the formation of a multilayered surface was explained. The maximum thickness of reaction zone and surface hardness achieved in the current work were 300 µm and 2470 HV, respectively.

In the present work microstructural evolution of A356 Aluminum alloy using an inclined cooling plate casting process for thixoforming feedstock production is investigated. The resultant microstructure was evaluated and compared with those of the same alloy produced by the conventional casting process, i.e. directly cast in the same mold without using an inclined cooling plate. It was found that when alloy melt poured over an inclined cooling plate and subsequently cast in semisolid condition into a metallic mould resulted in fine rosettes and nearly globular α-Al primary phase uniformly distributed in an Al eutectic matrix. The effect of the processing parameters such as the lengths and angles of the inclined cooling plate and their combinations were identified to produce alloy ingot with the most suitable microstructural constituent for thixoforming process

Nowadays, Ni-free austenitic stainless steels are being developed rapidly and high price of nickel is one of the most important motivations for this development. At present research a new FeCrMn steel was designed and produced based on Fe-Cr-Mn-C system. Comparative studies on microstructure and high temperature mechanical properties of new steel and AISI 316 steel were done. The results showed that new FeCrMn developed steel has single austenite phase microstructure, and its tensile strength and toughness were higher than those of 316 steel at 25, 200,350 and 500°C. In contrast with 316 steel, the new FeCrMn steel did not show strain induced transformation and dynamic strain aging phenomena during tensile tests that represented higher austenite stability of new developed steel. Lower density and higher strength of the new steel caused higher specific strength in comparison with the 316 one that can be considered as an important advantage in structural applications but in less corrosive environment