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

Twinning induced plasticity (TWIP) steels with high manganese percentage (17-35%), are mostly used in automotive bodies. Their microstructure at room temperature is austenitic, anddue to the low stacking fault energy, major deformation mechanism in them is twinning inside austenite grainswhich leads to enhanced mechanical strength in the steel. Due tothe important effect of heat treatment process on mechanical properties, full annealing heat treatment and resultant twins were investigated in this study.To this aim, the steel was casted, hot rolled, and then heat treated at different times and temperatures and the obtained microstructures were analyzed using optical microscope. The results showed that the percentage of annealing twinsis increased with increasing annealing temperature up to 1100 C, the peak point at which grain growth stage starts,and increasing temperature above that decreases twins’ percentage. A relation between grain size and annealing twins’ percentage was found. Full annealing temperature for this steel was determined to be 1100 C

In this research, the production of Fe-TiN and Fe-Ti(N,C) composite powders by mechanical alloying was investigated and evaluated. Ferrotitanium (containing 70%Ti), titanium and graphite were used as the raw materials. Initial mixtures were milled in different time durations under the pure nitrogen atmosphere with the pressure of 5atm. The results showed that when N2 pressure is 5 atm and milling time lasts 5 h, reaction starts and after 10 h, FeTi2 is completely converted to TiN. Also, the role of graphite as the active material of the reaction was investigated and it was found that it leads to the production of titanium carbonitride in the iron matrix

To find a suitable treatment in the preparation of Nb surface for platinum electrodeposition, different methods such as thermal oxidation, anodic oxidation, mechanical roughening, and mechanical roughening with subsequent anodic etching were examined. X-ray photoelectron spectroscopy was used to study the chemical composition of depth analysis of the surface. Moreover, in order to examine the morphology and surface roughness, the samples were analyzed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results showed that the most appropriate method for niobium surface preparation is mechanical roughening by shot blasting or abrading with emery and then anodic etching at the current density of 200A/m2 for 40 min. in a solution containing 95% methanol, 2.5% hydrofluoric acid, and 2.5% hydrochloric acid at the temperature of 35°C.

FSW material flow and phase transformation were studied at the interface of dissimilar welding of Al 6013 to Mg. Defect free butt weld was obtained when aluminum and magnesium test plates were placed in the advancing side and retreating side respectively, and the tool was placed 1 mm off the weld centerline into the aluminum side. In order to understand how the materials flow during FSW, steel shots were implanted as indexes into the test plate’s intimate face and welding was performed with determined optimum parameters. X-ray images were used to evaluate secondary positions of the steel shots at weld zone. It was revealed that steel shots implanted in the advancing side test plate were penetrated from advancing side into the retreating side with a relatively large rotational displacement of α. But shots implanted in retreating side test plate remained only in retreating side, without penetrating into the advancing side, and displaced by a low angle of β. It could be concluded that to reach defect free welds by FSW between two dissimilar metals, the tool should be inserted in harder metal and harder metal should be placed in the advancing side too. EDS analysis was performed in order to study formation and distribution of intermetallic phases in the welds interface. Two intermetallic compounds formed sequentially at Al6013/Mg interface were Al3Mg2 and Al12Mg17 in weld condition. Welded specimens were heat treated and their effects on mechanical properties of welds and formation of new intermetallic layers were investigated.

ZnO nanorods array films were coated on a glass template through a two-step chemical process. First, a sol-gel spin coating method was used to produce a ZnO seed layer and after that, the ZnO nanorods arrays were grown on it through a low temperature aqueous method. Synthesized films were studied by scanning electron microscope (SEM) and X-ray diffractometer (XRD). X-ray diffraction results showed single crystalline wurtzite with a c-axis preferential (002) orientation. The deposited ZnO layers had c-axis orientation, and showed a sharp X-ray diffraction peak at 2θ=34.40 degrees, corresponding to the (002) of hexagonal ZnO crystal. The SEM images showed vertical orientation of rods, and the diameters of rods were under 100nm. The photocatalytic degradation of XG6 azo dye in aqueous solutions was examined with a combination of ZnO nanorods array film as a photocatalyst and UV light. Results showed that the films are effective in decolorization of dye

Both Ti-6Al-4V and 316L stainless steels are widely used as engineering alloys. Fusion welding of these two alloys is not easily possible due to their incomplete solubility in each other. Brazing is one of the best choices for joining dissimilar alloys. In this study, wettability experiments were done at 940and 970ºC for 5, 15 and 30 min. Also, joining of these two alloys was carried out at 940 and 970ºC for 15 min. Optical and scanning electron microscope (SEM) were used for metallurgical observations. Moreover, mechanical properties of the brazed joint were investigated using microhardness test. The results showed that some reaction layers were composed in the brazed joint’s cross section. Ni-Ti intermetallic compounds were also observed in the brazed joint. Investigation of mechanical properties showed that hardness in the joint’s center is higher than base metals.

Gas tungsten arc welding is fundamental in those industries where it is important to control the weld bead shape and its metallurgical characteristics. However, compared to the other arc welding process, the shallow penetration of the TIG welding restricts its ability to weld thick structures in a single pass (~ 2 mm for stainless steels), thus its productivity is relativity low. This is why there have been several trials to improve the productivity of the TIG welding. The use of activating flux in TIG welding process is one of such attempts. In this study, first, the effect of each TIG welding parameters on the weld’s penetration depth was shown and then, the optimal parameters were determined using the Taguchi method with L9 (34) orthogonal array. SiO2 and TiO2 oxide powders were used to investigate the effect of activating flux on the TIG weld penetration depth and mechanical properties of 316L austenitic stainless steel. A camera was used to observe and record images of the welding arc, and analyze the relationship between increasing the penetration depth and arc profile. The experimental results showed that activating flux aided TIG welding has increased the weld penetration, tending to reduce the width of the weld bead. The SiO2 flux produced the most noticeable effect. Furthermore, the welded joint presented better tensile strength and hardness.