Advanced Materials Research Vol. 1119

Abstract: The SAE/ AISI 1045, a type of medium carbon steel, is used most commonly in various structural and element of machines. Sometime, it failed during the in-service, which assumed to be caused by cracking in material as the effect of casting, manufacturing, or heat treatment processes. The current research was developed to find out the effect of hardening and of tempering processes toward hardness, microstructure and cracking. The objectives of the current research are to obtain the effect of cooling rates toward the hardness and cracking and to define a proper cooling media to get a martensite microstructure without cracking of heat resistant products. Results showed that the chemical composition from the spectrometry test confirmed that the specimens were classified as AISI 1045 or JIS S45C. The hardness values properties increased with increase of temperature, except at 1000 °C. The specimens having the hardness property more than that of ASME II standard were not useable due to its brittle.

Abstract: The effects of Al, Co, Re, and Ru on the stacking fault energy in Ni alloys were analyzed using computational thermodynamics. The effects of adding up to 5 at% Re or Ru to a Ni-15at%Co system were found to be weak at 300 °C, 700 °C, and 900 °C. However, Al addition decreased the stacking fault energy in a Ni-15at%Co-Xat%Ru system, where X = 0, 3, 5. In addition, this decrease in the stacking fault energy due to Al addition became more significant as the amount of Ru increased. Furthermore, in Ni–Co–Al–Ru alloys containing 9at%Al, the addition of 5at%Ru decreased the stacking fault energy as much as the addition of 12.5at%Co at 900 °C. The effects of Co and Ru addition on the γ/γ’ microstructure of Ni-based superalloys were also discussed.

Abstract: This study examined the electrochemical deposition and dissolution of lithium on nickel electrodes in propylene carbonate-based electrolytes containing Al³⁺ or Zr⁴⁺ cations as a solid electrolyte interface (SEI)-forming additive. The electrode reactions were significantly affected by the Al³⁺ and Zr⁴⁺ cations. The cyclability of the electrodes was considerably improved in Zr⁴⁺-containing electrolyte solution. Scanning electron microscopy showed that the growth of dendritic lithium was greatly suppressed in the Zr⁴⁺-containing electrolyte solution. On the other hand, electrochemical impedance spectroscopy suggested that a relatively thinner SEI was generated on lithium metal from the Zr⁴⁺-containing electrolyte solution.

Abstract: Numerical simulations in machining processes are dependent on the flow stress input data. The flow stress is computed from empirical models which depend on number of material parameters, the values of which are derived from various mathematical optimization techniques. The derived flow stress parameters vary based on the nature of techniques used and the flow stress testing procedure utilized. This results in variations in the numerical simulation results when working with different models. In this work, the Johnson Cook flow stress model is tested for its sensitivity towards the finite element (FE) results. Orthogonal turning is conducted with AA 6082 (T6) aluminium alloy and the process is simulated in Deform 2D. The flow stress computed from the Johnson Cook model is input to the FE code and the cutting force and chip thickness recorded. The FE results are input to the Minitab statistical code and an optimization process conducted based on the orthogonal arrays concept. The comparative study reveals the sensitivity of the five parameters of the material model towards the cutting force and chip thickness.

Abstract: Since solid state welded joint is formed from an intimate contact between two metals at temperatures below the melting point of the base materials, the structural integrity of welding depends on time, temperature, and pressure. This paper provides some of examples of friction stir welding and diffusion welding process for aerospace components. Friction stir welding process of AA2195 was developed in order to study possible application for a large fuel tank. Massive diffusion welding of multiple titanium sheets was performed and successful results were obtained. Diffusion welding of dissimilar metals of copper and stainless steel was necessary to manufacture a scaled combustion chamber. Diffusion welding of copper and steel was performed and it is shown that the optimum condition of diffusion welding is 7MPa at 890°C, for one hour. It is shown that solid state welding processes can be successfully applied to fabricate lightweight aerospace parts.

Abstract: Since literature on the machinability of non laminated composites is scarce, an investigation was extended away to study the machinability of thick non laminated Glass Fiber Reinforced Plastic (GFRP) composites and to compare the above with machinability of thick laminated composites. The composites with high fiber weight fraction were drilled with a special geometry coated carbide drill (Ratio drill). Taguchi’s orthogonal array and analysis of variance (ANOVA) were used to examine the influence of process parameters (feed and spindle speed) on quality characteristics (thrust force and torque). The optimum degree of process parameters towards aperture quality was obtained.

Abstract: Laser surface melting was carried out on the surface of Ti-6Al-4V alloy with Ti-BN-C mixed powders. In this paper, an influence of the mole ratio of BN/ C on microstructure, chemical composition, element distribution and hardness were separately analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), electron probe micro-analyzer (EPMA) and Vickers hardness test (HV). The results showed that the melting layer mainly consisted of TiC_xN_1-x (x=0, 0.3, 0.7), TiB and Ti. The hardness was increased with improving the mole ratio of BN/C ratio.

Abstract: Crystalline Mg-Cu-Y alloy system was fabricated using the squeeze casting technique. Microstructure showed the multiphase structure composed of primary Mg rich phase distributed among the lamellae patterns, alternative layers of LPSO Mg phase and intermetallic phases. High microhardness and tensile strength of 104 HV and 223 MPa respectively were observed in the squeeze cast alloy. A good combination of compressive strength (706 MPa) and ductility (19%) was also achieved in the crystalline alloy which is unlikely to be attainable in amorphous Mg-Cu-Y system. The formation of LPSO phase in the current Mg-Cu-Y alloy mainly contributed to the high mechanical properties.

Abstract: In this study, an experimental investigation was conducted to determine the effects of cutting speeds and feed rates on surface roughness in turning of the Al %11Si and Al-11%Si-1% Bi die cast alloys. Experimental trials carried out on a CNC machine using coated carbide inserts (PVD). Three different cutting speeds, 70, 130 and 250 m/min and three feed rates 0.05, 0.1 and 0.15 mm/rev were used with a 0.15 mm constant depth of cut for all experiments. Additionally scanning electron microscope (SEM) was employed to clarify the different types of silicon morphology. Results revealed that surface roughness increased with increasing feed rate from 0.05 to 0.15 mm/rev and decreased with increasing cutting speed from 70 to 250 m/min. The result showed that workpiece containing Bi had the best surface roughness with lamellar silicon shape in comparison with aluminium-silicon with flake-silicon shape.

Abstract: Drilling is an essential secondary process for near net-shape of hybrid composite as to achieve the required dimensional tolerances prior to final application. Dimensional tolerance is often influenced by the surface integrity or surface roughness of the workpart. Thus, this paper aims to employ the Taguchi and response surface methodologies in minimizing the surface roughness of drilled carbon-glass hybrid fibre reinforced polymer (CGCG) using tungsten carbide, K20 drill bits. The effects of spindle speed, feed rate and tool geometry on surface roughness were evaluated and optimum cutting conditions for minimizing the aforementioned response was determined. Subsequently, response surface methodology (RSM) was utilised in finding the empirical relationships between experimental parameters and surface roughness based on the Taguchi results. The experimental analyses reveal that surface roughness is greatly influenced by feed rate and tool geometry rather than the spindle speed. This is due to the increment of feed that attributed to the increased strain rate and hence, deteriorated the surface roughness of the hybrid composite. The predicted results (via regression model) and theoretical results (via additivity law) were in good agreement with experiment results. This indicates that the regression model from response surface methodology (RSM) can be used to predict the surface roughness in machining of CGCG hybrid composite.