Machinability of Al-20Mg2Si-Cu metal matrix composite modified with bismuth or barium

Aluminum metal matrix composites (MMC) have been receiving growing attention largely owing to their excellent properties, such as excellent castability and mechanical properties. These properties make them useful for high performance applications, especially for lightweight components, particularly in the manufacture of automotive parts. Al-based composite reinforced with particulate Mg2Si phase has recently been shown to possess certain advantages. However, the mechanical properties of normal cast Al-20Mg2Si-Cu metal matrix composite are unsatisfactory due to the natural coarse morphology of the primary Mg2Si phase. Therefore, the melt treatment method with refiner elements was chosen due to improve the morphology of the Mg2Si reinforcement and achieve better mechanical properties. Most of MMC parts require some machining. However, the machinability of Al-20Mg2Si-Cu metal matrix composite is not well understood yet. By adding refiner elements to the composite, the mechanical properties and machinability including particle emissions will be affected. Therefore, the main objective of this thesis is to study the machinability, and mechanical properties of Al-20Mg2Si-Cu metal matrix composite containing bismuth or barium as modifier elements. Results from the different sections of this thesis demonstrate that modifier elements such as bismuth or barium improve the mechanical properties and machinability of the composite. Using modifier elements decreases ultrafine particle emissions during the machining process, which is beneficial for operator health. In addition, the proposed mathematical models for predicting surface roughness and cutting force for this composite are in good agreement with experiment data

Machinability of al-11si-2cu cast alloy modified by bismuth, strontium or antimony / Mohsen Marani Barzani

Aluminum-silicon alloys are notable materials owing to their fine thermal conductivity, low expansion coefficient and good corrosion that can be utilized in the fields of automotive industry such as cylinder blocks, cylinder heads, brake discs, pistons and valve lifters. Modification of melt treatment in Al-Si cast alloys leads to a change in the morphology of eutectic silicon, resulting in mechanical properties enhancement. This enhancement affects the machinability of Al-Si alloys (i.e. cutting forces, surface roughness, tool wear and chip morphology). Near-eutectic alloys are the most difficult to machine of the various Al-Si alloys because, the silicon phase present is almost ten times harder than the aluminum base alloy, which rapidly increases tool wear, these difficulties have thus created the need for a more in-depth understanding of the effects of microstructure on the machinability of these alloys. Compared with other techniques, melt treatment with addition of inoculation agents known as modifier or refiner elements is more practical method due to low production cost and suitability for general engineering applications. Despite previous studies on microstructure of Al-Si alloys, there is lack of information on the effect of Bi, Sb and Sr additions that extensively address the influence of these elements on machinability characteristics of Al-11Si-2Cu cast alloy when dry turning. Understanding the machinability of these alloys is imperative when it is necessary to fabricate some industrial products which are produced by casting process. Therefore, the aim of this research was to investigate the machinability characteristics of Al-11 Si2Cu alloy containing bismuth, antimony and strontium when dry turning using coated carbide inserts. The influence of additional elements on mechanical properties was also investigated by conducting hardness, tensile and impact tests. iv Machining of workpieces was completed using a CNC turning machine (ALPHA 1350S) with an 8.3 kW power drive. Various cutting speeds of 70, 130 and 250 m/min and various feed rates of 0.05, 0.1 and 0.15 mm/rev were employed. Pure Bi shots, pure Sb and Sr granules at concentrations of 1wt.%, 0.5.% and 0.04.% were selected based on the optimum concentration for each additive as determined by microscopic inspection. The results indicated that surface roughness and cutting force decreased with increasing cutting speed from 70 m/min to 250 m/min, additionally, change of silicon morphology from flake-like to lamellar structure affects the machinability parameters. It was found that the Bi-containing workpiece had the best surface roughness value and lowest cutting force due to formation of pure Bi which acts as lubricant on the machined surface, while Sr-containing workpiece produced the highest cutting force and highest surface roughness value. Bi-containing alloy produced segmentation chips (C-shape) in comparison with other alloy elements, which led to separation of chip segments at outer (free) surface. Sr and Sb-containing alloys increased ductility of alloys which led to the production of massive BUE during machining process, resulting in increased flank wear. Impact test shows that absorbed energy value for the base alloy was around 1.15J, whereas it increased to 2.2J for Sr treated alloy

Effect of machining parameters on cutting force when turning untreated and sb-treated al-11%si-1.8%Cu alloys using PVD coated tools

One of the important aspects of machining is the measurement of the cutting forces acting on the tool. The information of forces is required for evaluation of power requirements, designing tool holder, machine tool elements and fixture. In this research, the effect of cutting condition on cutting force when turning untreated Al-11%Si-1.8%Cu and Sb-treated alloys was investigated. PVD TiN coated insert as cutting tool under oblique dry cutting process utilized. Experiments were conducted at three different cutting speeds of 70, 130 and 250 m/min with feed rates of 0.05, 0.1 and 0.15 mm/rev, whereas depth of cut was kept constant at 0.05 mm. The results revealed that turning of Sb-treated alloys requires higher cutting force in comparison to untreated alloy. The cutting force values increased about four times with increasing feed rate from 0.05 mm/rev to 0.15 mm/rev. Furthermore, the cutting force decreased with increasing cutting speed from 70 m/min to 250 m/min

Increasing the productivity of the wire-cut electrical discharge machine associated with sustainable production

Wire-cut electric discharge machining is a nontraditional technique by which the required profile is acquired using sparks energy. Concerning Wire-cut electric discharge machining, high cutting rates and precision machining is necessary to improve productivity and achieve high quality of machined workpieces. In this research work, an experimental investigation was introduced to achieve higher productivity of the wire electrode associated with sustainable production in terms of product quality and less heat-affected zone. For this purpose, the effects of machining parameters including peak current, pulse on time and wire preloading were investigated using adaptive neuro-fuzzy inference system along with the Taguchi method. From this study, the optimal setting of machining parameters to achieve higher productivity and sustainability was identified. Moreover, Neuro-fuzzy modelling was successfully used to build an empirical model for the selection of machining parameters to achieve higher productivity at highest possible surface quality and minimum cost for sustainable production

Investigation into effect of silicon morphology on surface roughness while machining Al-Si-Cu-Mg alloy

Surface roughness is one of the key measures in manufacturing that describes machined surface integrity. In this research work, the effect of silicon morphology on surface roughness when turning Al-11%Si-1.8%Cu alloy and Sr-containing alloys was investigated. The experiments are carried out under oblique dry cutting conditions using a PVD TIN-coated insert at three cutting speeds of 70, 130 and 250 m/min, feed rates of 0.05, 0.1, 0.15 mm/rev, and 0.05 mm constant depth of cut. The result released that surface roughness decreased with adding 0.04 wt.% Sr to casting. The surface roughness values reduce with cutting speed increment from 70 m/min to 250 m/min. Also, the surface finish deteriorated with increase in feed rate from 0.5 mm/rev to 0.15 mm/rev

Investigating the Machinability of Al–Si–Cu cast alloy containing bismuth and antimony using coated carbide insert

Surface roughness and cutting force are two key measures that describe machined surface integrity and power requirement evaluation, respectively. This investigation presents the effect of melt treatment with addition of bismuth and antimony on machinability when turning Al–11%Si–2%Cu alloy. The experiments are carried out under oblique dry cutting conditions using a PVD TIN-coated insert at three cutting speeds of 70, 130 and 250 m/min, feed rates of 0.05, 0.1, 0.15 mm/rev, and 0.05 mm constant depth of cut. It was found that the Bi-containing workpiece possess the best surface roughness value and lowest cutting force due to formation of pure Bi which plays an important role as a lubricant in turning process, while Sb-containing workpiece produced the highest cutting force and highest surface roughness value. Additionally, change of silicon morphology from flake-like to lamellar structure changed value of cutting force and surface roughness during turning

White layer thickness prediction in WEDM-ANFIS modeling

<p>Wire Electric Discharge Machining (WEDM) is a nontraditional technique by which the required profile is acquired using spark energy. Regarding wire cutting, precision machining is necessary to achieve high product quality. White Layer Thickness (WLT) is one of the most important factors for assessing superior surface finish. In this research, Adaptive Neuro-fuzzy Inference System (ANFIS) was used to predict the WLT in WEDM using coated wire electrode. The predicted data were compared with measured values, and the average prediction error for WLT was 2.61 %.</p

Effect of barium on the structure and characteristics of Mg2Si reinforced particles Al–Mg2Si–Cu in situ composite

Addition of barium (Ba) in various concentrations is susceptible to cause changes on Mg2Si reinforced particles in Al–Mg2Si–Cu in situ composite. In this study, six samples of the composite with different concentrations of Ba (0.1–0.8 wt%) were prepared. The alteration of Mg2Si structure, phase reaction characteristics and cooling curves behaviour of the composite were investigated via optical microscope, scanning electron microscope (SEM), and computer aided cooling curve thermal analysis (CACCTA). The results depicted that 0.2 wt% exhibit the appropriate concentration of Ba added in order to modify and refine the Mg2Si particles. The skeleton and dendrite shape of Mg2Si particles have been transformed into fine polygonal shape accompanied with decreased in average size from 1178.5 µm of the unmodified particles to 289.1 µm. In fact, the refinement of Mg2Si particles is associated with the increased of nucleation temperature, TN of the respective phase together with the least undercooling, ΔU correspond to the easiness of the particles to be formed prior to its growth. Meanwhile, the decrement of TN respective to other concentrations of Ba indicates the opposite refinement effect of the particles as it became coarser. Besides, the refinement of Mg2Si has induced more nucleation of the particles resulting the increment of the density of particles and better distribution over the composite area. Therefore, the corresponding mechanical and tribological properties of the composite are believed to be improved accordingly