Influence of Cu content on microstructure and mechanical properties of thixoformed Al−Si−Cu−Mg alloys

The effects of Cu content on the microstructure and mechanical properties of thixoformed Al−6Si−хCu−0.3Mg (х= 3, 4, 5 and 6, mass fraction, %) alloys were studied. The samples were thixoformed at 50% liquid content and several of the samples were treated with the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy(SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis, as well as hardness and tensile tests. The results show that the cooling slope casting and thixoforming process promote the formation of very fine and well distributed intermetallic compounds in the aluminium matrix and the mechanical properties of the alloys increase considerably compared with the permanent mould casting. The results also reveal that as the Cu content in the alloy increases, the hardness and tensile strength of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed heat-treated Al−6Si−3Cu−0.3Mg alloy are 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat-treated alloy with high Cu content (6%) are 361 MPa, 274 MPa and 1.1%, respectively. The fracture of the thixoformed Al−6Si−3Cu−0.3Mg alloy shows a dimple rupture, whereas in the alloy that contains the highest Cu content (6%), a cleavage fracture is observed

The effects of mg addition on the microstructure and mechanical properties of Thixoformed Al-5%Si-Cu alloys

In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 C for 8 h, quenching in warm water at 60 C, followed by aging at 155 C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of a-Al globules and the eutectic silicon in the samples. It was also observed that a compact p-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed

An overview of semisolid processing of aluminium alloys

Semisolid metal processing (SSM) or thixoforming is a new technology that offers several advantages over liquid processing and solid processing. This process utilizes semisolid behavior as well as reduces macrosegregation, porosity, and forming forces during shaping process. A lot of research work has been carried out by various researchers in order to exploit the potential of this process to produce different products especially for automotive industry. This paper will summarise the rheological behavior of aluminium alloys in semisolid slurries, thixoformability of modified aluminium alloys, the effect of feedstock production method on mechanical properties, and the importance of developing low-cost raw materials for semisolid processing

Influence of iron on phase stability and corrosion resistance of Ti-15%Cr alloy

In this study, the effect of Fe addition on the phase stability and corrosion resistance of Ti-15%Cr alloys was investigated. The alloying phenomenon in the specimens was also investigated to determine the effectiveness of the application of pure metallic powders as raw materials for the powder metallurgy method. Ti-15%Cr-1%Fe alloys exhibited needle-like structures within equiaxed structures, while Ti-15%Cr-5%Fe and Ti-15%Cr-10%Fe alloys only showed equiaxed grains. XRD results showed that the β phase could be stabilized by the addition of 5% or more Fe to the alloy. Although the pure powders were used as raw materials, the designated chemical composition, i.e. Ti-15%Cr-(1~10)%Fe can be achieved during sintering. The alloying phenomenon occurred upon sintering due to the high diffusivity of Cr and Fe within the β Ti matrix. The corrosion resistance of the newly developed Ti-15%Cr alloys was significantly improved compared with a commercial Ti-6%Al-4%V alloy

Entropy-Based Approach for Fatigue Crack Growth Rate of Dual-Phase Steel

This paper presents an entropy-based approach for the fatigue crack growth of dual-phase steel under a constant amplitude loading. According to the degradation-entropy generation theorem, the degradation coefficient can be derived from the correlations of entropy and crack propagation.  The temperature evolutions induced for the duration of the fatigue crack growth tests on the as-received and dual-phase steel till it failed were measured to ensure their validity. The results of the present model and the calculated Paris-regime crack growth data were analysed to reach the conclusion that the temperature at the surface of a specimen during a fatigue crack growth test can be used for the assessment of fatigue crack growth by the intensity of the degradation coefficient. The predicted results showed that the present model could accurately predict the fatigue crack growth rate of dual-phase steel with a regression value (R2) of 0.9952

Pembentukan mikrostruktur berbentuk sfera dalam keadaan separa pepejal aloi aluminium Al-4.8Si-2.8Cu-0.5Mg

Hasil penyelidikan mengenai pembentukan mikrostruktur berbentuk sfera dalam keadaan separa pepejal aloi aluminium Al-4.8Si-2.8Cu-0.5Mg dibentangkan dalam penulisan ini. Bahan awal aloi aluminium tersebut dihasilkan melalui proses tuangan konvensional. Mikrostruktur bahan awal terdiri daripada struktur dendrit dan antara dendrit yang halus. Mikrostruktur aloi berubah kepada bentuk bukan dendrit (bentuk roset) yang halus apabila leburan bahan awal aloi tersebut dituang ke atas plat keluli cerun penyejuk yang dicondongkan pada sudut kecondongan 60° dengan suhu tuangan 650°C dan panjang cerun penyejukan 400 mm, sebelum dibiarkan memejal di dalam acuan keluli yang dipanaskan terlebih dahulu pada suhu 150°C. Pembentukan mikrostruktur berbentuk sfera dalam matriks cecair berjaya dihasilkan apabila bilet aloi yang mengandungi mikrostruktur bukan dendrit dipanaskan semula secara pantas sehingga suhu separa pepejalnya pada 575°C dengan menggunakan sistem pemanasan secara aruhan berfrekuensi tinggi (30-80 kHz, 35 kW). Bilet aloi yang berada dalam keadaan separa pepejal berjaya dibentuk-tikso ke dalam acuan keluli yang dipanaskan terlebih dahulu dengan menggunakan mesin penekan silinder hidraulik yang membekalkan daya tekanan 20 kN dengan kelajuan maksimum 85 mm/s. Hasil daripada proses pembentukan-tikso menunjukkan ira matriks α-aluminium yang berbentuk sfera bertaburan secara seragam di samping tidak terdapat keporosan di sepanjang sampel. Proses rawatan haba T6 yang melibatkan rawatan haba larutan pada 480°C selama 8 jam, lindapkejut dalam air panas pada suhu lebih kurang 60°C dan diikuti proses penuaan pada suhu 155°C selama 4 jam dilihat menyumbang kepada taburan partikel-partikel dengan lebih sekata

Improvement of energy absorption on magnesium alloy mixed carbon-nanotube and lead reinforcement materials in terms of high velocity impact

This paper presents the fracture behaviour of magnesium alloy (AZ31B) with the reinforcement of carbon-nanotube (CNT) and lead subjected ballistic impact. Magnesium alloys are material that can absorb impact energy, however the absorption energy can be increased with the alloy reinforcement with nano-partial. This paper leads to two parts which are experiment and simulation of gas gun. The projectile used was a cone-nose type with diameter of 11 mm made by steel series 1006. The simulation used Cowper-Symonds model to see material behaviour with 25 mm thickness. The correlation of the experiment and simulations was evaluated to see the accuracy of simulations made. It was shown that the value of R2 was 0.9588 where simulation can be used to predict the ballistic impact on 600 m/s velocity. From the simulation results, it was found that the depth of penetration for Magnesium alloy AZ31B reinforced with CNT and Pb showed good agreement findings. The depth of penetrations onto the simulation were obtained between 15 to 25 mm. The added reinforcement materials provide a reduction in the depth of penetration of 40% compared to the original Magnesium alloy AZ31B. Thus, this type of magnesium alloy reinforced with CNT and Pb is suitable for ballistic resistant panel with weight saving determination on armoured vehicle.Â

Homogenous Dispersion And Interfacial Bonding Of Carbon Nanotube Reinforced With Aluminum Matrix Composite: A Review

Recent developments in the field of carbon nanotube (CNT) have attracted attentions on a new development of aluminum matrix composite (AMC). Homogenous dispersion and interfacial bonding of CNT/metal matrix are the two main problems yet to have sound solutions.In general, to ensure uniform dispersion, the overall process can be divided into three steps: preprocessing, mixing and post processing. This paper summarizes previousworks on solid and liquid processing techniques which some are more successful than others by looking at the improvement of the composite tensile strengths. On the other hand the interfacial bonding depends on the existance of Al4C3 phase and physical conditions of CNT. Both elements must be controlled for the optimized results. The review presented here would be used as references in the future works to fabricate higher strength CNT/aluminum composite

Development of low liquid fuel Burnera

Recently, most of the gas turbine combustion research and development involves in lowering the emissions emitted from the combustor. Emission causes adverse affect to the world and mankind especially. Main concern of the present work is to reduce the NOx emission since the CO emission could be reduced through homogeneous mixing of fuel and air. Homogeneous mixing of fuel and air is also needed in order to reduce NOx emission. A liquid fuel burner system with radial air swirler vane angle of 30o, 40o, 50o and 60o has been investigated using 163mm inside diameter combustor. Orifice plates with three different sizes of 20mm, 25mm and 30mm were inserted at the back plate of swirler outlet. All tests were conducted using diesel as fuel. Fuel was injected at two different positions, i.e. at upstream and downstream of the swirler outlet using central fuel injector with single fuel nozzle pointing axially outwards. Experiment has been carried out to compare the three emissions NOx, CO and SO2. NOx reduction of about 53 percent was achieved for orifice plate of 20mm with downstream injection compared to orifice plate of 20mm with upstream injection. CO2 and SO2 was reduced about 26 percent and 56 percent respectively for the same configuration. This comparison was taken using swirler vane angle of 60o. The overall study shows that larger swirler vane angle produces lower emission results compared to the smaller ones. Smaller orifice plates produce better emission reduction. Meanwhile, downstream injection position significantly decreases the emission levels compared to upstream injection position. Combination of smallest orifice plate and largest swirler vane angle with downstream injection produce widest and shortest flame length