Band 30, Heft 3

The present paper deals with the evaluation of different vacuum heat treatments on the microstructure of a low alloyed sintered Fe-[1.5 Cr-0.2 Mo]-0.6 C steel. Different gas pressures were applied on the material during cooling from the sintering temperature. The average cooling rates were calculated in the range of 1453 K to 673 K and were varying from 0.1 to 6 K/s, according to the gas pressure applied (0 to 600 kPa). Mechanical properties have been evaluated in terms of toughness, plasticity and hardness. The results show that increasing the nitrogen pressure resulted in an increased amount of bainite/martensite microstructure with high level of properties achieved.

The anisotropy of the creep properties and fracture using small punch tests for the Al-Al 4 C 3 system produced by ECAP were analysed in this work. Small punch creep tests under constant force were performed at the temperature of 623 K. It was shown that the fracture results, i.e. time to fracture and deflection at fracture were different in specimens with different orientation with respect to the axis of ECAP deformation. Fracture surface analysis of the tested small punch specimens was conducted. Fractures have transcrystalline ductile character. The fracture dimples are equiaxial as well as elongated in the dependence on strain direction. Fracture dimples are of two categories, the small ones sized from 0.1 to 0.5 μm and large ones ranging from 3 to 6 μm.

Study of the recovery of pig iron from dry red mud through plasma smelting has been done. The reductant used was graphite. Various fluxes were used for the formation of slag. The parameters varied were smelting time, basicity and concentration of reductant and fluxes. It was observed that the reduction kinetics improved progressively with the increase of all the variables up to certain level and on further increase the metal recovery decreased. The results were interpreted kinetically and rate determining step was evaluated. Multi Linear Regression Analysis studies were carried out. The variables were subjected to Principal Component Analysis. Four factors could explain 75.4% of the variables.

Surface treated montmorillonite (MMT) was used to prepare nanocomposites with poly(amide-imide) (PAI) 5 by solution intercalation technique with various percent of organoclay (5–15 mass %). Surface modification of the MMT was performed with Cloisite 20A for ample compatibilization with the PAI matrix. The PAI 5 chains were produced through polycondensation of 4,4-diamino diphenyl sulfone 4 with N -trimellitylimido- L -alanine 3 in a medium consisting of triphenyl phosphite, N -methyl-2-pyrolidone (NMP), pyridine and calcium chloride. The PAI-Nanocomposites morphology and clay dispersion were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and PAI chains on the properties of PAI-Nanocomposites films were investigated by using UV-Vis spectroscopy, thermogravimetric analysis (TGA) and water uptake measurements. Thermal stability of nanocomposites increased relative to the neat polyamide with increasing organoclay content but water uptake of these materials decreased as compared to the neat polyamide indicating reduced permeability.

New type of aromatic polyamide/montmorillonite nanocomposites were produced using solution process in N -methyl-2-pyrolidone. Amide chains were synthesized from 4,4′-diaminodiphenyl sulfone and p -phenylenediacrylic acid in N -methyl-2-pyrolidone. The resulting nanocomposite films containing 5–15 mass % of organoclay were characterized for FT-IR, scanning electronmicroscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), optical transparency and water absorption measurements. The distribution of organoclay and nanostructure of the composites were investigated by (XRD) and SEM analyses. Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. The percentage optical transparency and water absorption of these hybrids was found to be much reduced upon the addition of modified layered silicate indicating decreased permeability.

A titanium-modified 14Cr-15Ni-2Mo austenitic stainless steel, known as alloy D9, has been chosen as the material for the fuel cladding and hexagonal wrapper of the Prototype Fast Breeder Reactor presently under construction at Kalpakkam. The alloy is generally produced by double vacuum melting process consisting of Vacuum Induction Melting (VIM) followed by Vacuum Arc Remelting (VAR). An alternate route consisting of vacuum induction melting followed by electro slag refining (ESR) has been employed to produce the alloy with lower inclusion content Tensile studies were carried out at various temperatures between ambient and 1023 K at an interval of 50 K and strain rate of 1.2 × 10 –3 s –1 on the steels in 20% coldworked condition. Tensile properties of both VAR grade and ESR grade material were found to be similar. The influence of the secondary processing routes on the mechanical properties of alloy D9 is studied.

Structure of CaO-B 2 O 3 -TiO 2 glass system has been studied by Raman spectroscopy in this work. The influences of TiO 2 content and molar ratio of CaO to B 2 O 3 on the structure of CaO-B 2 O 3 -TiO 2 glasses were examined. Experimental results indicate that TiO 2 exists in the form of [TiO 4 ] or forms B-O-Ti linkage, [BTi 4 O 10 ] –1 structure units, in the system, and produces a certain destructive effects to large borate groups and induces to form some relatively small structure units. The increase of CaO does damages to the B-O-Ti linkage and large borate groups, simultaneously leading to the formation of relatively small units. Thus, both TiO 2 and CaO impair borates network structure and weaken the glass-forming ability of borates in CaO-B 2 O 3 -TiO 2 glass system.

This study investigated physical and mechanical properties of the light medium density fiberboard (MDF) panels made from thermally treated wood fibers of eucalyptus camaldulensis at three different temperatures (393 K, 423 K or 453 K) for 30 or 60 min in a laboratory autoclave. The average thickness swelling of the panels decreased by 16–54% depending on the treatment temperature and time. However, the modulus of rupture, modulus of elasticity, and internal bond strength decreased by 16–37%, 9–25% and 10–39%, respectively. Based on the findings obtained from the present study, it may be said that wood fibers of E. camaldulensis treated at 453 K – 30 min can be used in the light MDF manufacture for use in humid conditions, such as kitchen and bathroom furniture requiring improved dimensional stability.

Fe-Ni-Al 2 O 3 cermet materials were prepared, and the electrolysis with these anodes were performed in cryolite-based electrolyte consisted of 44NaF-40AlF 3 -8NaCl-5CaF 2 -3Al 2 O 3 (wt%) at 850 °C. The purity of produced aluminium is 97–98%, while the calculated anodic corrosion rate is 18.2 mm/a–24.0 mm/a. The EPMA analysis showed that there is an oxide scale consisting of Fe 2 O 3 and FeAl 2 O 4 on the anode working surface. The homeostasis of dissolution and formation of oxide scale makes the thickness of the oxide scale and the cell voltage stable within a certain range. The dissolution of oxide scale results in the presence of FeF 3 in the electrolyte. By analysis of the corrosion process, it shows that low temperature, high alumina concentration and low CR electrolysis is preferred for using Fe-Ni-Al 2 O 3 inert anodes for aluminium electrolysis.

This paper studied the effects of Austenization with pulsed electric field (PEF) on a low-carbon steel. The results showed that the vol. % lath martensite and Brinell hardness of the specimens quenched with the PEF decreased, especially under the condition of higher frequency, lower voltage, shorter processing time and lower capacity. In addition, the heat treatment with the PEF increased the Ac1 point to a higher temperature as much as 90°C at least and maintained Ac3 point unchangeably. The PEF was able to refine martensite structure.

Manufacturing process is significantly altered by tool wear and this factor creates intricate issues that form a hindrance in attaining manufacturing automation. The other vital parameters determining the tool life are the dimensional accuracy and surface roughness of the workparts. In this research work, an attempt is being made to conduct machining studies on martensitic stainless steel AISI410 to analyze the effect of crater wear and surface roughness in TiN coated WC tool. The crater wear and surface roughness values are initially recorded. The recorded data are used as input in the ANOVA plinth and subsequently used for developing mathematical tool wear models using multiple regression analysis (MRA). The results from ANOVA reveal that the cutting speed influences the surface roughness more significantly than feed rate and depth of cut. Further, it is emphasized that, the crater wear is affected more by feed rate as compared to the cutting speed. Consequently, the metallographic studies using scanning electron microscope (SEM) are conducted based on which the effects of crater wear on the TiN coated WC cutting tool are plotted and analyzed.

The isothermal oxidation behavior of Cu-38at.%Zn alloy over the temperature range of 773–1123 K was studied. Characterization of the oxidized specimens was conducted using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the oxidation kinetics of Cu-38at.%Zn alloy obeys parabolic law. The activation energy during oxidation of the alloy is calculated to be 176 kJ mol –1 , based on the parabolic growth constant analyses. An external ZnO oxide scale, internal ZnO oxide and a Zn depletion zone on substrate formed after alloy oxidation are discussed. The scale spallation from the substrate is analyzed, based on the growth stresses and thermal stresses induced during oxidation.