Journal of advanced materials and processing
Volume:1 Issue: 2, Spring 2013

Mechanical properties of alloys have a strong relation with microstructure and determination of their behavior can lead to multiple advantages. To obtain this goal, finite element method)FEM(is one of the best ways. In this study a series of experiments were carried out on the produced Ti-6Al-4V to obtain its mechanical characteristics and to prepare it for photographing in micro dimensions. Next, using scanning electron microscopy (SEM), images were taken from some regions of the manufactured Ti-6Al-4V. In the next step, a method was developed to separate alpha-phases from beta-phases with a relatively high accuracy. At the end of this stage, the images were mapped into a matrix involving arrays which show the type of the phases. A code is written which maps the material matrices to the FEM model. The Gurson model is an appropriate model for simulating the damage inside the ductile material. Results of simulations obtained from SEM images show that the simulation data are in good agreement with experimental results and also analysis of simulation clearly shows that the failure always happens in boundaries between two different phases; ductile and brittle, and then growth over them to form the final failure of the material.

In this study, electrochemical deposition of Ni-SiC-Gr nano composites was studied. The Watts bath was used for electrodeposition. The SiC and graphite powders were suspended in the electrolyte and stirred. The effects of changes in bath stirring rate on the composite coating were investigated. The X-Ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) methods were used to characterize the micro structure of deposited layer. The results showed that the micro-hardness at the first stage increases with increases in stirring rate value. The coating that precipitated at 500 rpm showed maximum hardness. Analysis of microstructure with SEM showed a homogeneous and uniform distribution of elements in the coated layer. The optimum condition for electrodeposition were as: pH=4.2, current density= 4A/dm2, stirring rate =500 rpm and 45˚C.

In this study, the effect of deposition regime on the wear behavior of VK8 coating applied to 1.2344 tool steel by electro spark method (ESA) was investigated. After sample preparation, the coating with high and low regime was applied. To assess the wear behavior, the pin on disk test method according to ASTM G99-04, was used. For surveying surface morphology and cross section of the coating as well as the substrate, optical microscope and SEM were used. Also for phase evaluation of the coating, X-ray diffraction (XRD) was used. The results show that the imposed regime is very impressive on the thickness of coating and wear resistance. In low regime, less porosity, better finishing surface and lower coating thickness was achieved. In this regime, better wear resistance was obtained.

In the current study, a thermal model was used to investigate the effects of welding parameters on the distribution of temperature in wide gap aluminothermic rail welds. To solve the governing thermal equation, SUTCAST, a finite difference program (FDM) was employed while different aspects such as phase change and convective heat transfer in weld pool were taken into account in the numerical solution. To validate the predictions, the modeling results were compared with the experiments and despite some utilized simplifications, a reasonable agreement was found between numerical and experimental results. The effects of welding variables such as preheating; initial liquid temperature and weld gap on temperature distribution were studied. The results of the modeling showed that the magnitude of weld gap had the greatest influence on thermal behavior of the joint and the highest weld gap results in most stable results.

Large strains, anisotropy of mechanical properties of materials and Coulomb friction in contact regions are some properties in the analysis of deep drawing process. In this research, the effects of different parameters such as anisotropy coefficient, work hardening exponent and friction coefficient on deep drawing process of drawing quality steel are studied. For this purpose, the finite element method (FEM) to simulate the process is used. A 2D finite element simulation (axis symmetric) in ABAQUS is done and the results are validated with valid appropriate reference. Then Forming Limit Diagrams (FLD) for different friction coefficients, different anisotropy coefficients and different work hardening exponents are obtained. Finally, changes in FLD are discussed and it is observed that the friction coefficient is the most effective parameter on FLD and anisotropy coefficient and work hardening exponent are the least effective parameters on FLD.

Both Zirconium-based alloys and 321stainless steel are widely used as engineering alloys due to their good mechanical properties. Conventional fusion welding techniques for Zr alloys and stainless steel are not feasible due to the formation of brittle intermetallic compounds such as (Zr3Fe, ZrFe2 and Zr2Fe) and corrosion cracking. Brazing is one of the most widely used techniques for joining dissimilar alloys.Using titanium base filler metal decreases the diffusion and the formation of brittle intermetallic compounds. In this study, wetting experiments were done at 820, 850, 865ºC and 3, 5, 7 and 10 min. Also, joining of these two alloys was carried out at 850 and 865ºC for 10 and 15 minutes. Optical microscope, scanning electron microscope (SEM), XRD, shear test and micro-hardness test were used for metallurgical and mechanical investigations. The results show that 20 ºC/min heating and cooling rates at 850ºC and 10 min brazing condition lead to a proper joint without any brittle intermetallic compounds.

In this research the effect of initial microstructure on hot deformation behavior in terms of Ferrite-to-Austenite ratios is studied. Two types of stainless steels C1 and C2 were homogenizing heat-treated and deformed under hot compression examinations at temperatures 900ºC and 1100ºC at strain rate of 0.1s-1. The results showed that the flow stress levels of specimens are strongly related to deformation parameters and initial microstructures of steels. Moreover, during cooling from 1350ºC to the deformation temperature, flow stress level increased for both samples because of increment in austenite content.