Journal of advanced materials and processing
Volume:3 Issue: 1, Winter 2015

Bending process is one of the most significant fields of application of sheet metal die. In bending process, it is quite vital that the product should have the desired angle. Furthermore, in order to obtain the desired angle in the bent parts, spring-go and spring-back amounts must be known. In this study, 30o, 60o and 90o bending processes were applied to S235JR (1.0038) sheet metal having 3, 4, 5 and 6 mm thickness. These materials were bent in three forms as heat-untreated, normalized and tempered. In addition to this, the bending process was carried out by making the punch waited on the material for 30 seconds (30 s-punch-wait bending) and by removing the punch without waiting (direct bending). As a result of the experiments it was determined that while the amount of spring-go increased in 30o bending process depending on the thickness of the material, it decreased in 60o and 90o applications. It was also determined that the amount of spring-go in 30 s punch-wait bending process was less than that of the direct bending process. Finally, the effects on the bending process and deformation of heat treatment were revealed by micro-structural characterization.

Ultrasonic vibration assisted single point incremental forming (UVaSPIF) is based on localized plastic deformation in a sheet metal blank. It consists to deform gradually and locally the sheet metal using vibrating hemispherical-head tool controlled by a CNC milling machine. The ultrasonic excitation of forming tool reduces the vertical component of forming force. In addition, application of ultrasonic vibration reduces the surface roughness of the specimen. Surface roughness is one of the quantitative and qualitative parameters, which is used to assess the quality of the final product. In the present paper, a statistical analysis and optimization of effective factors on this parameter is performed in the UVaSPIF. For this purpose, response surface methodology (RSM) is selected as the experiment design technique. The controllable factors such as vertical step size, sheet thickness, tool diameter, wall inclination angle, and feed rate is specified as input variables of the process. The obtained results from analysis of variance (ANOVA) and regression analysis of experimental data confirm the accuracy of mathematical model. Furthermore, it is shown that the linear, quadratic, and interactional terms of the variables are effective on the surface roughness parameter. To optimize the surface roughness parameter, the finest conditions of the experiment are determined using desirability method, and statistical optimization is subsequently verified by conducting the confirmation test.

In this study, WC–20 wt.% equiatomic (Fe,Co) powder mixture was milled in a planetary ball mill. The effects of different milling time (15 min, 5h, 10h, and 25 h) and sintering temperatures on the microstructure and mechanical properties of this equi-Fe substituted cermet were investigated. The structural evolution and the crystallite size changes of the powders during milling were monitored by X-ray diffraction (XRD). Microstructure developments of the samples were examined using scanning electron microscope (SEM). The results showed that the crystalline size of WC and internal strain were 22 nm and about 1.1 % after 25 hours of milling, respectively. The hardness and the relative density of the WC-20wt.% (Fe,Co) composites consolidated by conventional sintering at different temperatures, ranging from 1150 to 1450 ˚C in hundreds, were investigated. The optimized sintering temperature was measured at 1350°C. At a constant sintering temperature, 1350°C, the highest relative density of 98.2% and hardness of 1281 (HV30) were obtained for the milling time of 25h.

Nanostructured zinc oxide (ZnO) was successfully synthesized by precipitation method using the extract of Cylea barbata Miers (CBM) leaves as a soft template after 3 h of calcinations in furnace at 500oC in the open air. Characterization results showed that the nanostructured ZnO had hexagonal wurtzite structure with space group P63mc and nano-scale particle diameter. It was suggested that the existence of polysaccharide galacturonic acid as the major biomolecular component in the CBM extract induced the formation of the nanostructured ZnO. Preliminary study results through activity testing of adsorbtion for Congo red (CR) dye removal from aqueous solution showed that the nanostructured ZnO exhibited excellent adsorption property, indicating that its adsorption activity was better than that of the commercial ZnO. Regeneration study of the nanostructured ZnO indicated that it could be reused while it sadsorption activity was kept excellent with removal efficiency >85% even up to five times of the cycling experiments.

In this study, the effects of mechanical milling and YSZ reinforcing on oxidation behavior of CoNiCrAlY coatings were investigated. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with commercial CoNiCrAlY powder and milled for 24 hrs. Then, the mechanically milled and commercial powders were deposited on Inconel 617 substrate using High Velocity Oxygen-Fuel (HVOF) process. Freestanding bodies of nanostructured and conventional HVOF CoNiCrAlY coatings were oxidized at 1000 °C for different times to form the thermally grown oxide layer. X-ray diffraction analysis, scanning electron microscopy and X-ray mapping were used to analyze the scales formed on the surface of the oxidized samples. The results showed that nanostructured coatings exhibited higher porosity due to undesirable morphology of feedstock powders. This factor accelerated diffusion rate of oxygen into coating body. On the other hand, undesireable oxidation of nanostructured particles during spraying leads to increase in the oxidation rate of coatings.

Mold powders are used as raw materials in continuous casting of steel industry; Also they are mostly composed of aluminum, calcium, silica oxides, alkaline and earth-alkaline oxides along with carbon and fluor. Two of the most important duties of mold powders are the lubrication of the space between mold walls and steel shell, and heat transfer control between steel shell and the copper mold. Fluor is one of the most important constituents of mold powders and is employed to control viscosity in order to obtain favorable lubrication and solidification temperature control in order to control heat transfer. The fluor in the mold powder is added to it with the aid of some fluorided compounds like fluorine (CaF2). This study has used Fluorine to make a powder similar to the reference sample, with the use of portland cement clinker and fluorine. Moreover, groove viscometer studies have been conducted here to compare sample viscosities to the viscosity of the reference sample. In addition XRD as well as SEM analyses were conducted. As a result, crystalline phase of cuspidine was found in the glass matrix indicating that the chemical compound in sample 1 may be a suitable substitute, as compared to the reference sample, for the mold powder used in continuous casting steel industry.

Thermal stability and the kinetics of the grain growth of nano-crystalline Mg-6Al-1Zn-1Si alloy prepared via mechanical alloying (MA) were investigated. It started with elemental powders, using a variety of analytical techniques including differential scanning calorimetry (DSC), X-ray diffraction method (XRD), and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The results showed that MA-processed alloy was composed of an Mg-based supersaturated solid solution with small amounts of Al and MgAl2O4. Grain growth and Mg2Si precipitation occurred upon annealing of the MA-processed Mg-based alloy. Nevertheless, grain growth in the MA-processed alloy was limited and α-Mg grains with sizes in the range of 70 nm were still present after exposure to 450 °C. The grain growth behavior of alloy can be described by the parabolic kinetic equation of grain growth. Higher strength values obtained after hot consolidation can be due to refined microstructure and the formation of Mg2Si intermetallic phase.

Bi2Mn2O7 nano-powders were synthesized via a stoichiometric 1:1 Bi:Mn molar ratio hydrothermal method at 180 °C for 48 h in a 1M NaOH aqueous solution; and solid state method, using Bi(NO3)3.5H2O and MnO2 as raw materials. The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique. Also, the rietveld analysis was done in FullProf in profile matching mode. It was found that Bi2Mn2O7 crystallizes in a cubic crystal structure with space groupFd3 ̄m. The size and morphologies of the synthesized materials were studied by transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) techniques, respectively. The FESEM images showed that the synthesized Bi2Mn2O7 has rod like structure in hydrothermal method and a mixture of rod and particle structures in solid state method. Also, BET-BJH analysis investigated for determination of pore size, pore volume, average particle size, pore width and surface area of the obtained materials. Also, photoluminescence spectra of the obtained materials were studied.