The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

AbstractIn 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 1.2wt%) 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 8h, quenching in warm water at 60°C, followed by aging at 155°C for 4h. 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 α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8wt% and 1.2wt%. 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 1.2wt%Mg) with its ultimate tensile strength (UTS) as high as 306MPa, yield strength (YS), 264MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2wt%), cleavage fracture was observed

Microstructural refinement and corrosion resistance improvement of heat-treated A356 alloy processed by equal channel angular pressing

The microstructure refinement, hardness and corrosion resistance of heat-treated A356 aluminium alloy processed by equal-channel angular pressing (ECAP) were investigated. ECAP was carried out at room temperature using a mold, with a channel angle of 120° via route A. Results of the investigation confirm that the flaky coarse silicon particles were effectively fragmented from 4.22 to 0.761 μm and the grain size reduced from 171 to 40 μm after four passes of heat-treated as-cast using ECAP process. ECAP processing increases the hardness of heat-treated as-cast alloy from 61 Hv to 125 HV after four passes. Heat-treated A356 alloy shows enhanced corrosion resistance from 0.0424 to 0.00149 mmy-1, after four passes. In this research, ECAP processing has been shown to improve the hardness and corrosion resistance of as-cast A356 alloy

Effects Of Mechanical Stirring And Short Heat Treatment On Thixoformed Of Carbon Nanotube Aluminium Alloy Composite

The present work aimed to determine the effects of thixoforming and short T6 heat treatment processes on the microstructure and mechanical properties of thixoformed A356 alloy reinforced with 0.5 wt% multi-walled carbon nanotube (A356-MWCNT). The semisolid composite feedstock was produced by a mechanical stirring route followed by thixoforming, and finally, it was heat treated with a shorter solution treatment and artificial ageing hours. A premix of 0.5 wt% magnesium (Mg) as wettability agent and MWCNT was injected into molten A356 alloy at 650 °C. Mixing and stirring were performed by a using three-blade impeller at 500 rpm for 10 min, and the mixture was poured into a preheated mould. Microstructure studies show the mechanical stirring effects on the transformation of dendritic arms to mostly globular and rosette structures of α-Al. The formations of more spheroidised structure of eutectic silicon (Si) were predominant after the heat treatment, thereby revealing the effectiveness of shorter T6 heat treatment. Results of field emission scanning electron microscopy images showed uniform distribution and pull-out structures of MWCNT throughout the matrix, thereby justifying the effective load transfer and wettability between reinforcement and alloy matrix. Subsequently, the mechanical properties of the composite shown significant improvements after each stage. The yield strength (YS), ultimate tensile strength (UTS) and elongation to fracture of cast A356 alloy increased from 115 MPa, 132.9 MPa and 1.8% to 135 MPa, 178.3 MPa and 3.1% respectively, in the A356-MWCNT. Consequently, these properties were further improved to 180 MPa, 255.8 MPa and 5.7% after the thixoforming process. The highest attainment of yield strength (YS), ultimate tensile strength (UTS) and elongation to fracture after short T6 of A356-MWCNT were 215 MPa, 277.0 MPa and 7.6%, respectively. The hardness of the samples was improved from 59.5 HV in as-cast alloy to 106.4 HV in thixoformed short T6 A356-MWCNT

Industrial Training as Gateway to Engineering Career: Experience Sharing

AbstractToday's engineering education demands in-depth theoretical knowledge as well as hands-on exposure to the profession. Traditionally, theoretical engineering education is achieved in campus through direct teaching and laboratory learning. However, hands-on exposure or real world confrontation provides engineering students with on-the-job experience. This helps them to decide whether their skills and industry are a good match. For specialised industries, such as manufacturing, aerospace and electronics, industrial training provides the opportunity for students to gain the most rewarding and enlightening working experience in related companies. This paper examines the industrial training experience gained by the students through a 12-week attachment period specifically looking at whether the companies have been successful in providing a relevant engineering workplace experience. A few industrial training experiences by students will be shared highlighting the positive and negative aspects. This study also suggests some steps that can be taken to ensure companies run industrial training programs that do meet the faculty's expectation

Kebolehbentukan-tikso aloi 2014 dengan penambahan Si dan pengurangan Cu

Dalam kajian ini, kebolehbentukan-tikso aloi aluminium (Al) 2014 dengan penambahan unsur silikon (Si) dan pengurangan unsur kuprum (Cu) dikaji. Kandungan Si dan Cu dalam aloi 2014 diubah suai supaya kriteria kebolehbentukan-tikso dapat dipenuhi. Kebolehbentukan-tikso aloi 2014 dan aloi Al-terubah suai diukur secara termodinamik dengan menggunakan pakej perisian JMatPro dan seterusnya dibuktikan secara uji kaji melalui analisis terma dan analisis fasa. Hasil kajian ini mendapati bahawa sifat kebolehbentukan-tikso aloi 2014 dapat dipenuhi dengan penambahan Si dan pengurangan Cu. Apabila kandungan Si dalam aloi 2014 bertambah, kandungan fasa eutektik pada titik ‘lutut’ tertinggi yang terbentuk di atas lengkung pecahan cecair meningkat dengan ketara, manakala julat suhu pemejalan pula semakin mengecil. Di samping itu, pengurangan Cu pula menyebabkan julat suhu pemprosesan untuk pembentukan-tikso menjadi semakin luas lalu mengakibatkan sensitiviti pecahan cecair pada titik ‘lutut’ tertinggi menurun. Selain pembentukan fasa Al2Cu dan fasa θ-Al5Cu2Mg8Si6, kemunculan fasa π-Al8FeMg3Si6 dengan struktur yang padat hasil daripada pengurangan Cu juga dijangka menyumbang kepada peningkatan sifat mekanik aloi Al-terubah suai. Akhir sekali, aloi Al-terubah suai tersebut dijangka mampu digunakan untuk menghasilkan komponen otomotif seperti rod penyambung, aci sesondol dan aci engkol melalui proses pembentukan-tikso

Observing the behaviour of reinforced magnesium alloy with carbon-nanotube and lead under 976 m/s projectile impact / M.F. Abdullah ...[et al.]

This paper presents the effects of reinforced magnesium alloy, AZ31B with carbon-nanotube (CNT) and lead (Pb), in terms of ballistic resistance. Magnesium alloys possess high energy absorption capability for impact resistance. However, its capability is limited and needs to be enhanced to resist ballistic impacts. The addition of a reinforcement material within the magnesium alloy, such as CNT or Pb, can improve impact resistance. This study is divided into two ballistic test methods, namely experiment and simulation. The samples involved are the original AZ31B and reinforced AZ31B with CNT and Pb. The projectile type used for ballistic testing was a 5.56 mm FMJ NATO at a velocity of 976 m/s and the thickness of the plate was 25 mm. The aim is to study the ability of the plate against the ballistic resistance. The ballistic experiment utilises a high speed camera, at 100,000 fps, to capture the impact occurring on the plate’s surface. A Cowper-Symonds model is used for the ballistic simulation and indicates the ballistic resistance of the reinforced AZ31B with increments of CNT and Pb. The velocity of the projectile penetrating through the plate was reduced by over 45% compared to the original AZ31B alloy. Reinforcement using CNT and Pb on AZ31B improved the ballistic resistance behaviour and therefore, this material is suitable for use on ballistic panel

The Need to generate a Force Time History Towards Life Assessment of a Coil Spring / Y.S. Kong...[et al.]

This paper presents the generation of force time history for coil spring fatigue life predictions using cumulative trapezoidal numerical integration of acceleration time histories. Loading time history was a crucial element for fatigue life prediction but a suitable instrument for the data collection was not always available. Hence, the required force time histories were generated from two relative acceleration time histories. Acceleration time histories from vehicle sprung and un-sprung mass were collected and converted into displacement using cumulative trapezoidal numerical integration approach. Through regarding the spring as a linear component, the force time history was obtained. The force time history together with the spring finite element model were used as the input to fatigue life models for fatigue life prediction. The predicted fatigue lives for the coil spring were 3.12× 10-6, 5.67 × 10-6, 6.97 × 10-6 blocks to failure using Coffin-Manson, Morrow, Smith-Watson-Topper model respectively. The results were validated using measured strain time history where the Morrow and Smith-Watson-Topper models’ results were fitted perfectly using the conservative correlation approach

INVESTIGATIONS ON THIXOJOINING PROCESS OF STEEL COMPONENTS

This research is to develop a carbon composite prepared from carbon coir fibers that is reinforced with epoxy resin. Carbon coir fibers were taken from three types of coir fiber specifically designated as CKCF, CYCF and CRCF. The samples were prepared using epoxy resin reinforced with carbon at different weight percentages for three types of coir fiber starting with 0wt.%, 2wt.%, 4wt.%, 6wt.%, 8wt.% and 10wt.%. The mechanical properties such as tensile stress and impact strength were used to characterize all the samples. The morphological study of reinforced samples was also conducted in this research using a SEM machine. The characteristics of all the composite materials were also investigated and discussed. It was determined that the CKCF sample exhibited better mechanical properties than the other coir fiber composites, having a higher average tensile stress value at 11.80MPa and higher impact strength values ranging from 268J to 276J at different carbon content. CKCF with 10wt% AC content had a tremendous impact strength compared with CYCF and CRCF

Characterising Ballistic Limits of Lightweight Laminated-Structure as a Protective Panel for Armoured Vehicle / N.A. Rahman...[et al.]

This study investigates the ballistic performance of aluminium alloy Al7075-T6 and magnesium alloy AZ31B served as the intermediate layer in triple-layered laminated panel using computational analysis. Aluminium and magnesium alloys offer a considerably potential for reducing the weight of an armoured vehicle body due to low densities and high energy absorption capabilities. The poor ballistic performance of these materials can be improved by layering with the high strength steel, Ar500. A commercial explicit finite element code was implemented to develop triple-layered panels impacted by a 7.62 mm armour piercing projectile at velocity range of 900 to 950 m/s. Two models were constructed where aluminium alloy and magnesium alloy served as intermediate layer in the first model and the second model respectively. The ballistic performance of each model in terms of ballistic limit velocity and depth of penetration was evaluated. Considering the 25% existing armour vehicle weight reduction, it was found that magnesium alloy has equivalent ballistic limit to that of aluminium alloy which is at 1020 m/s. At the standard projectile velocity, aluminium stopped the projectile at 24 mm depth and magnesium stopped at 25 mm. Thus, lightweight materials can be suitable combinations for designing lighter armoured vehicle panel without neglecting its ballistic performance

Appraisal of a high protein distiller’s dried grain (DDG) in diets for European sea bass, Dicentrarchus labrax fingerlings on growth performance, haematological status and related gut histology

High protein distiller's dried grains (HP‐DDG) are co‐products of ethanol production that uses prefractionation technology. An 8‐week growth trial was conducted to investigate the effect of partial replacement of soybean meal (SBM) by three levels of HP‐DDG (30%, 40% and 50%) on growth performance, physiological parameters and histological changes of the intestine of European sea bass, Dicentrarchus labrax. The results indicated that an increased dietary level of HP‐DDG of more than 30% significantly increases growth performance and improved the FCR of sea bass. In addition, replacement of SBM by HP‐DDG enhanced feed intake efficiency and the health status of fish. Haematology and serum biochemistry (haemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs), packed cell volume (PCV %) and humeral immune parameters including total protein, albumin, globulin, cholesterol, lysozyme activity and total antioxidant capacity significantly increased with increase HP‐DDG inclusion levels. The findings of this study indicated that HP‐DDG is a good complementary protein source for inclusion aquaculture diets and levels above 30% as a replacement of SBM did not compromise growth performance and physiological parameters of sea bass while enhancing some important indices of health status in this species