Advanced Materials Research Vol. 410

Abstract: Cryogenic treatment of cutting tool material has been reported improving properties of the materials, resulting improved performance. Tungsten carbide is most accepted and widespread cutting tool material in the industry. Cryogenically treatment of tungsten carbide has shown favorable results. However, still much is unknown about the treatment for improvement in properties of the materials, to make the process identical to the existing conventional heat-treatment process in implementation. Importance of tempering during cryogenic treatment has also been reported, however hardly we find any documentation regarding the effect of the number of tempering cycles during cryogenic treatment. This work is based upon to know the effect of the number of tempering cycles during cryogenic treatment of tungsten carbide tool material. Comparison study was done for untreated and cryogenically treated tungsten carbide inserts following variable number of tempering cycles during the treatment, in turning process. The performance was evaluated in terms of tool wear, power consumption and surface roughness achieved. Cryogenically treated inserts have shown favorable results. At low cutting conditions, performance was better and has not got affected by the number of tempering cycles whereas the number of tempering cycles during cryogenic treatment does effects at high cutting conditions, and two or three tempering cycles has shown better results.

Abstract: The preparation of γ-MnOOH nanorod and Mn₃O₄ nanooctahedra have been achieved via hydrothermal reaction between KMnO₄ and DMF in water without the use of any surfactant or template. Various measurements were used to characterize the structure, morphology and electrochemical behavior of the resultant products. A possible growth mechanism has been proposed, the reaction temperature and the concentration of DMF plays a crucial role in the formation of the products. Their electrochemical properties have also been discussed.

Abstract: A huge number of different process types are in use to produce magnesium-based composites. Depending on the reinforcement type, all the processes can be subdivided into solid state or powder metallurgical (PM) and liquid phase or ingot metallurgical (IM) processes. In this paper we will focus on ingot metallurgy processes. These liquid state processes result quite often in a very good interface of reinforcement with the magnesium matrix. The liquid processes can be further subdivided into infiltration techniques, casting processes and spray deposition. Those are the most inexpensive processing technologies for discontinuous, reinforced magnesium-based composites. When produced using melting processes, nanoparticle-reinforced magnesium composites are expected to improve in strength, due to the grain refinement described in the Hall-Petch relation. When an isotropic distribution of nanoparticles is achieved, the composites are additionally expected to be Orowan-strengthened. That is why nanosized reinforcements are expected to represent the future for improving the properties of magnesium-based metal matrix composites.

Abstract: Metal matrix composites (MMCs) have received considerable attention due to their excellent engineering properties. Accuracy and surface finish play an important role in modern industry. Undesired projections of materials, known as burrs, reduce the part quality and negatively affect the assembly process. In this study, reducing burr size in drilling of MMC is performed by adding ultrasonic vibration to the process. Al/SiC_p MMC with 5 wt% of SiC particulates in dry drilling operation with HSS drill tools coated with TiN was investigated. The effect of ultrasonic assistance on burr size was studied. The results demonstrate that under suitable ultrasonic vibration conditions, in comparison with the conventional drilling, the burr height and width could be reduced.

Abstract: High temperature deformation behavior of Al–5.9%Cu–0.5%Mg alloy and Al–5.9%Cu–0.5%Mg alloy containing 0.06 wt.% of Sn was studied by hot compression tests at various temperatures and strain rates. Addition of trace amounts of Sn into the Al–Cu–Mg alloy system resulted in a significant increase of flow stress for all conditions of temperature and strain rate. 100% and 89% of the flow stress values during hot deformation could be predicted within ± 10% deviation values for the aluminum alloys with and without Sn content, respectively, by artificial neural network (ANN) modeling. From the deformation mechanism maps and microstructural investigation, the safe process regimes for hot working of the base alloy was identified to be at (i) very low strain rate (< 0.003 s⁻¹) at temperature < 450 °C, and (ii) high temperature (> 400 °C) with strain rate > 0.02 s⁻¹. For the micro-alloyed alloy, it was at low strain rates (< 0.01 s^-1) for the entire temperature range studied. Flow softening for both alloys was observed to be at low strain rates and was identified to be due to dynamic recrystallization (DRX). The metallurgical instability during deformation was identified due to shear band formation and/or inter-crystalline cracking.

Abstract: The main aim of the work is to analyze the influence of welding speed and tool rotation speed on the forming behavior of FSW blanks. The FSW blanks are made of 6061 Al sheet of 2.1 mm thickness. The welded sheets are made at two different optimized levels of welding speed (90 and 100mm/min) and tool rotation speed (1300 and 1400 rpm). The effect of FSW parameters on the forming limit curve (FLC) and thickness distribution was analyzed by performing limit dome height (LDH) tests at few pre-defined stretching strain paths. It is observed that FSW blanks exhibit more formability as compared to un-welded sheets. The forming limit is found to improve with increase in tool rotation speed and it decreases with increase in welding speed. An attempt has been made to relate the thinning gradient developed during necking with the forming limit at different welding conditions.

Abstract: Prediction of shear plane angle is a way for prediction of the mechanism of chip formation, machining forces and so on. In this study, Merchant and Lee-Shaffer theories are used for prediction of shear plane angles and cutting forces in machining of Al/SiC_p MMC with 20% of SiC as reinforcement particles. The experimental cutting forces are compared with the calculated cutting force based on shear plane angles extracted from Merchant and Lee-Shaffer theories. The variation of these cutting forces with cutting speed, feed rate and depth of cut has been discussed. The results showed that Merchant theory may be used as a good method for prediction of chip formation in machining of Al/SiC_p MMC.

Abstract: Mesh-less methods belong to a new class of numerical methods in computational mechanics and offer several advantages over the conventional mesh-based methods. They enable modelling of processes involving high deformation, severe discontinuities (e.g. fracture) and multiple physical processes. These types of situations are usually encountered in arc welding, rendering its modelling suitable via mesh-less methods. In this paper, a mesh-less Element Free Galerkin (EFG) method has been developed to model the heat transfer during welding. The results predicted by the EFG method are found to be in close agreement with those obtained by the finite element method and those observed in welding experiments. This demonstrates the effectiveness and utilities of the EFG method for modelling and understanding the heat transfer processes in arc welding.

Abstract: The flexural properties of SLG filled phenolic composites have been determined in previous study. It is time consuming to prepare the samples for the tests. In addition, it is even more time consuming to carry out the tests and analyze the results. It is therefore necessary to develop a mathematical model that will predict the flexural properties of particulate filled phenolic composites. Mathematical models for tensile strength, Young’s modulus are available but not for impact strength, flexural strength and fracture toughness. There is no sign that it can be built up from simple mathematical model; polynomial interpolation using Lagrange’s method was therefore employed to generate the flexural properties model using the data obtained from experiments. From experiments, it was found that the trend of the flexural properties of the samples post-cured conventionally was similar to that post-cured in microwaves; it is therefore possible to predict the flexural properties of the samples post-cured in microwaves from the mathematical model generated for flexural properties of samples post-cured in a conventional oven. The workload is therefore halved as the process of generating the mathematical was much faster and simpler.

Abstract: Epoxy resin was filled with glass powder with a view to increasing strength of the composite for structural applications by a research Centre on composites, University of Southern Queensland (USQ). In order to reduce costs, the Centre wishes to fill as much glass powder as possible subject to maintaining sufficient strength of the composites in structural applications. This project varies the percentage by weight of the glass powder in the composites which are then subjected to flexural tests. The results show that composite with 25 % by weight of the glass powder produces the highest flexural strength and Young’s modulus combined with a reasonable fluidity for casting; the highest flexural strain was achieved when the percentage by weight of glass powder is 10 %.