Materials Science Forum Vols. 773-774

Abstract: This work investigates the effect of lubrication parameter on the operation performance of a high-speed spindle using a micro-mist lubrication system. Experiments are conducted through a long-time spindle test under different combinations of oil-supply parameter and rotating speed for a micro-mist lubricated spindle. The correspondent relationships among temperature rise, vibration, oil-supply parameter and rotating speed are established through the experiments under moderate oil-supply. The results show that the better oil-supply parameter combinations exist under different spindle rotating speeds, which could ensure the sufficient and adequate lubricating oil film to be formed and a stable elasto-hydro-dynamic lubrication could be further created during the operation period. The minimization of the temperature rise in bearings may be attained. Increasing air pressure contributed to the reduction in bearing temperature, but saturation might be appeared after the pressure level reached to a certain extent. The dynamic response measurement shows that this prototype spindle has an overly large vibration and rotation unbalance on the radial plane, which highlights the unstable operation problem of the spindle. Therefore, it is necessary to improve the constructed procedures, such as design, manufacture, and assembly for further use, to enhance the operation performance of the spindle. The analysis, measurement and diagnosis procedures established in this study could be helpful to uplift the related techniques for precision machinery industry.

Abstract: Aluminium silicon alloy (AlSic) matrix composite reinforced with aluminium nitride (AlN) particle is a new generation material for automotive and aerospace application. This material has low density, light weight, high strength, high hardness and stiffness. Metal Matrix Composit (MMC) material is one of the advanced materials which have good future prospects. This paper presents the study of tool wear and surface roughness investigation when milling AlSi/AlN Metal Matrix Composite using uncoated carbide cutting tool. The volume of AlN reinforced particle was 10%. The milling process was carried out under dry cutting condition. The uncoated carbide insert parameters used were cutting speed of (250-750 m/min), while feed rate and depth of cut were kept constant at 0.15 mm/tooth of 0.3mm respectively. The Sometech SV-35 video microscope system and Mitutoyo surface roughness tester were used for tool wear measurements and surface roughness respectively. The results revealed that the tool wear increases with cutting speed (450 m/min). While at high cutting speed, the surface finish improves. It was found that the cutting speed of 750m/min was optimum condition for obtaining smooth finish and longer tool life. Keywords: AlSi/AlN Metal Matrix Composite milling process, tool wear, and surface roughness, uncoated cemented carbide tool

Abstract: Textured self-lubricated tools were designed and fabricated. Dry cutting tests were carried out on with these self-lubricated tools and a conventional tool. The tool wear and the friction coefficient at the tool chip interface were measured. It was shown that the tool wear and the friction coefficient of the textured self-lubricated tools were reduced compared with that of the conventional tool. Two mechanisms responsible were found, the first one is explained as the formation of a lubricating film with low shear strength at the tool-chip interface, which was released from the texturing and smeared on the rake face, and served as lubricating additive during dry cutting; the other one was explained by the reduced contact length at the tool-chip interface of the textured tools, which contributes to the decrease of the direct contact area between the chip and rake face. It is suggested that the using of textured self-lubricated tools is an effective way to reduce the tool wear in dry cutting.

Abstract: High productivity, low cost and high profits in machining processes is important aspects in aerospace, automotive and tool/die metal manufacturing industries. However, the dynamic deflection of tool and work piece systems generates unstable cutting forces when machining with high material removal rate. The main focus of this paper is the study of variable tool geometries effect on chatter stability. A semi discretization method (SDM) was utilized to predict numerical chatter using variable helix, pitch and variable helix and pitch tools effect at high radial immersion. The results showed that variable helix and variable pitch milling tools exhibit better unstable behavior at 25 percent radial immersion.

Abstract: In this paper, the optimization of cutting parameters is investigated to assess surface roughness and cutting force in the end milling of AlSi/AlN metal matrix composite. Eighteen experiments (L18) with five factors (cutting speed, feed rate, depth of cut, volume of particle reinforcement, and type of coated insert) were performed based on Taguchi designs of the experiment method. Two types of coating (TiB₂ and TiN/TiCN/TiN) of the carbide cutting tool were employed to machine various volumes of AlN particle (5%, 7% and 10%) reinforced AlSi alloy matrix composite under dry cutting conditions. Signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were applied to investigate the optimum cutting parameters and their significance. The S/N analysis of the obtained results showed that the optimum cutting conditions for the cutting force were; A₂ (triple coating of the insert), B₂ (cutting speed: 200m/min), C₁ (feed rate: 0.6mm/tooth), D₁ (axial depth: 0.6mm) and E₁ (5% reinforcement). At the mean time, the optimum cutting conditions for surface roughness were; A₁ (single coating of insert), B₃ (cutting speed: 250m/min), C₂ (feed rate: 0.75mm/tooth), D₁ (axial depth: 0.6mm) and E₁ (5% reinforcement).The study confirmed that, with a minimum number of experiments, the Taguchi method is capable of determining the optimum cutting conditions for the cutting force and surface roughness for this new material under investigation.

Abstract: This research presents the performance of Aluminum nitride ceramic in end milling using using TiAlN and TiN coated carbide tool insert under dry machining. The surface roughness of the work piece and tool wear was analyzed in this. The design of experiments (DOE) approach using Response surface methodology was implemented to optimize the cutting parameters of a computer numerical control (CNC) end milling machine. The analysis of variance (ANOVA) was adapted to identify the most influential factors on the CNC end milling process. The mathematical predictive model developed for surface roughness and tool wear in terms of cutting speed, feed rate, and depth of cut. The cutting speed is found to be the most significant factor affecting the surface roughness of work piece and tool wear in end milling process.

Abstract: This paper presents the development of a new polymer matrix composite (PMC) material for use in injection molding machine. The material consists of iron powder filled in an acrylonitrile butadiene styrene (ABS) and surfactant powder material. In this study, the effect of iron powder was investigated as a filler material in polymer matrix composite and ABS was chosen as a matrix material. The detailed formulations of compounding ratio by volume percentage (vol. %) with various combinations of the new PMC are investigated experimentally. Based on the result obtained, it was found that, vol. % increment of iron filler effected on the hardness, tensile and flexural strength. With highly filled iron content in ABS composites increase the hardness and tensile strength of PMC material through an injection molding process.

Abstract: Silicon nitride possess excellent hot hardness and wear resistance coupled with very good corrosion resistance. Hence, in recent years, silicon nitride has been a serious contender as a reinforcement to develop light weight metal matrix composites for several technological applications. Al6061 is most popular matrix alloy as it possess excellent formability and in particular the quality of extrudates of Al6061 is quite high and are the most preferred in space and naval applications especially for support structures and torpedoes blades respectively. Improved corrosion and slurry erosion resistance on use of silicon nitride in nickel and aluminum alloy matrices have been reported by several researchers. In the light of the above, this paper focuses on development of Al6061-6wt% Si₃N₄ by stir casting the most economical and popular route followed by hot extrusion. Hot extrusion was carried out using 200T hydraulic press at extrusion ratio of 1:10 at a temperature of 550°C. Slurry erosion tests were carried out using 3.5% NaCl solution containing silica sand particles of size 312μm at different rotational speeds varying between 300 rpm and 1200 rpm. The sand concentration was varied from 10g/l to 40 g/l. Under identical test conditions, hot extruded Al6061-6wt% Si₃N₄ composite do possess better slurry erosion resistance when compared with matrix alloy. The mechanism involved in the material removal process during slurry erosion process will also be discussed.

Abstract: Bulk metallic glasses (BMGs) are amorphous alloys that exhibit unique mechanical properties such as high strength due to their liquid-like structure in the vitreous solid state. While they usually exhibit low ductility, they can be toughened by incorporating secondary phase particles within the amorphous matrix via composite fabrication to generate amorphous metal matrix composites (MMCs). Traditional MMCs are fabricated at high temperature in the liquid state with tedious blending processes. This high temperature processing route often leads to unwanted reactions at the reinforcement/matrix interface, creating brittle intermetallic by-products and damaging the reinforcement. In the present work, novel bulk metallic glass composites (BMGCs) were fabricated at low processing temperatures via thermoplastic forming (TPF) above the glass transition temperature of the amorphous matrix. Here, the unique thermophysical features of the matrix material allow for TPF of composites in non-sacrificial moulds incorporating various types of reinforcement, via processing in the solid state at low temperatures (less than 200 °C), within a short timeframe (less than 10 minutes); this avoids the formation of brittle phases at the reinforcement/matrix interface leading to efficient bonding between particles and matrix, thereby creating a tough, low density composite material.

Abstract: This study reports the glass forming ability (GFA) of Al-Ni-Si alloys with selected compositions based on atomic packing efficiency and driving force criteria. Higher GFA was observed in the Al-rich lower liquidus temperature regions of the Al-Ni-Si system indicating that these compositions exhibit a lower driving force for crystallization. Five glassy alloys that were calculated to consist of densely packed atomic short-range ordering were found to retain an amorphous structure upon copper mould casting. The result of GFA in the Al-Ni-Si system provides a novel approach to develop new metallic glasses considering both the thermodynamic stability and sluggish crystallisation kinetics through efficient packing.