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

Properties of Natural Rubber/Recycled Chloroprene Rubber Blend: Effects of Blend Ratio and Matrix

AbstractThe present study investigated the effects of two types of natural rubber and different blend ratios on the cure, tensile properties and morphology of natural rubber/recycled chloroprene rubber blends. The blends of natural rubber/recycled chloroprene rubber were prepared by using laboratory two-roll mill. The result showed that the cure time prolonged with the addition of recycled chloroprene rubber (rCR). Comparability, natural rubber/recycled chloroprene rubber (SMR L/rCR) blendcured rapidly than epoxidized natural rubber/recycled chloroprene rubber (ENR 50/rCR) blend. The addition of rCRalso caused a decrement in the tensile strength and elongation at break for both rubber blends. The SMR L/rCR blendsshowed higher tensile strength and elongation at break compared to those of ENR 50/rCR blends at any blend ratios

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

DISTRIBUTION AND DIVERSITY OF FUSARIUM SPECIES ASSOCIATED WITH GRASSES IN TEN STATES THROUGHOUT PENINSULAR MALAYSIA

Fusarium  is one of   the  important genera associated with grasses as saprophytes, endophytes and  pathogens. A  study was  carried  out  on  distribution  and  diversity  of  Fusarium  species associated  with  two  groups  of   grasses  in  10  states  throughout  Peninsular  Malaysia  i.e. agricultural  grasses  (Oryza  sativa  and  Saccharum  officinarum)  and  non-agricultural  grasses (Axonopus compressus, Centhotheca lappacea, Chloris barbata, Crysopogon aciculatus, Cyanadon dactylon, Dactyloctenium  aegyptium, Digitaria  ciliaris,  Echinochloa  colona,  Eleusine  indica,  Eragrostis  amabilis, Eragrostis malayana, Eragrostis uniloides, Ischaemum magnum, Panicum brevifolium, Panicum millaneum, Panicum repens, Paspalum  commersonii, Paspalum  conjugatum, Paspalum orbiculare, Pennisetum purpureum, Sacciolepis  indica, Sporobolus diander and Sporobolus  indicus). A  total of  474  isolates were single-spored and  identified by morphological characteristics. F.  semitectum was  frequently  isolated (23.6%), followed by F. sacchari and F. fujikuroi with 15.4% and 14.6%, respectively. The other nine species were F. solani (10.3%), F. proliferatum (8.9%), F. oxysporum (7.4%), F. subglutinans (6.5%), F.  equiseti  (5.5%), F.  verticillioides  (3.4%), F.  compactum  (2.5%), F.  chlamydosporum  (1.1%) and F. longipes (0.8%). Based on the Shannon-Weiner Index, F. solani was the highest (H' = 2.62) isolated from grasses. Species of  Fusarium from O. sativa were widely diverse with 11 species, followed by non-agricultural grasses with nine species and S. officinarum with only six species. This  is  the  first  report on diversity of  Fusarium associated with grasses  in Malaysia.Key words: Oryza  sativa,  Saccharum  officinarum,  non-agricultural  grass,  Fusarium  species, diversity  and Graminea

Distribution and Diversity of Fusarium Species Associated with Grasses in Ten States Throughout Peninsular Malaysia

Fusarium is one of the important genera associated with grasses as saprophytes, endophytes and pathogens. A study was carried out on distribution and diversity of Fusarium species associated with two groups of grasses in 10 states throughout Peninsular Malaysia i.e. agricultural grasses (Oryza sativa and Saccharum officinarum) and non-agricultural grasses (Axonopus compressus, Centhotheca lappacea, Chloris barbata, Crysopogon aciculatus, Cyanadon dactylon, Dactyloctenium aegyptium, Digitaria ciliaris, Echinochloa colona, Eleusine indica, Eragrostis amabilis, Eragrostis malayana, Eragrostis uniloides, Ischaemum magnum, Panicum brevifolium, Panicum millaneum, Panicum repens, Paspalum commersonii, Paspalum conjugatum, Paspalum orbiculare, Pennisetum purpureum, Sacciolepis indica, Sporobolus diander and Sporobolus indicus). A total of 474 isolates were single-spored and identified by morphological characteristics. F. semitectum was frequently isolated (23.6%), followed by F. sacchari and F. fujikuroi with 15.4% and 14.6%, respectively. The other nine species were F. solani (10.3%), F. proliferatum (8.9%), F. oxysporum (7.4%), F. subglutinans (6.5%), F. equiseti (5.5%), F. verticillioides (3.4%), F. compactum (2.5%), F. chlamydosporum (1.1%) and F. longipes (0.8%). Based on the Shannon-Weiner Index, F. solani was the highest (H' = 2.62) isolated from grasses. Species of Fusarium from O. sativa were widely diverse with 11 species, followed by non-agricultural grasses with nine species and S. officinarum with only six species. This is the first report on diversity of Fusarium associated with grasses in Malaysia

Effect of Radiation on Magnetohydrodynamic Free Convection Boundary Layer Flow Near the Lower Stagnation Point of a Solid Sphere with Newtonian Heating

In this paper, the effect of radiation on magnetohydrodynamic free convection boundary layer flow near the lower stagnation point of a solid sphere with Newtonian heating, in which the heat transfer from the surface is proportional to the local surface temperature, is considered. The transformed boundary layer equations in the form of partial differential equations are solved numerically using an implicit finite difference scheme known as the Keller-box method. Numerical solutions are obtained for the local wall temperature, the skin friction coefficient, as well as the velocity and temperature profiles. The features of the flow and heat transfer characteristics for various values of the Prandtl number Pr, magnetic parameter M, radiation parameter and the conjugate parameter are analyzed and discussed

A REVIEW ON OPTIMISTIC IMPACT OF CLEANER PRODUCTION ON MANUFACTURING SUSTAINABILITY

As a continuous application of an integrated environmental strategy, Cleaner Production (CP) is seen to have a substantial impact in establishing a sustainable manufacturing system. Thus, this paper explores and discusses intensively the impacts and benefits gains from the CP implementation that influences the sustainability development. The findings show that CP have optimistic impact on manufacturing competency, environment and economics performance which considered most significant influence on sustainability. Besides, economic performance was identified as an ultimate goal in manufacturing sustainability that can be enhanced significantly by competency and environmental performance. This paper provides the correct translational process of CP in order to achieve high level of sustainable manufacturing practice included the specific characteristics of performances. It can be referred as a guideline for manufacturing firms to define and measure performance based on CP implementation

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

Morphological evolution during partial re-melting of AISI D2 cold-work tool steel

The impact of isothermal temperature and holding time on the microstructural evolution process is studied. This process is used to produce globular microstructures during partial re-melting of AISI D2 cold work tool steel. The experimental results showed that the optimum process factors should be selected according to the criteria for average grain size and shape factor and also by acknowledging the distribution of the liquid phase around the grains. With increasing isothermal temperature and holding time, the liquid phase starts to diffuse into the grain boundaries and spread more evenly. Also, the equiaxed grains were transformed into near-globular shape, which makes the grain size and shape factor more favourable for thixoforming. The work shows that the optimal process condition for the thixoforming of AISI D2 is 1340°C and 5-min holding time, having a shape factor of 1.13 and a particle size of 51 μm

Permodelan termodinamik aloi al-Si-Cu untuk pemprosesan logam separa pepejal

Pembentukan-tikso merupakan teknologi baharu untuk menghasilkan produk hampir siap dalam keadaan separa pepejal. Proses ini dapat mengurangkan makropengasingan, keliangan serta memerlukan daya pembentukan yang rendah. Sehingga kini, terdapat beberapa aloi aluminium seperti gred A319, A356 dan A357 digunakan untuk pemprosesan logam separa pepejal. Oleh itu, terdapat permintaan untuk mempelbagaikan aloi aluminium daripada gred yang lain untuk pemprosesan logam separa pepejal. Kajian ini membincangkan tentang permodelan termodinamik untuk meramal perubahan sifat aloi aluminium gred A319 apabila kandungan elemen pengaloian seperti tembaga, mangan dan ferum dipelbagaikan agar memenuhi kriteria pemprosesan logam separa pepejal. Kesemua pengiraan dalam kerja permodelan ini menggunakan perisian komersial ‘Java-based Material Properties’ (JMatPro). Pengiraan termodinamik berdasarkan persamaan ‘Scheil’ digunakan untuk menentukan julat suhu pemejalan (ΔT), kepekaan pecahan cecair (dfL/dT) dan suhu tingkap pemprosesan (ΔT30/50). Daripada pengiraan termodinamik, didapati suhu pemejalan aloi yang telah ditingkatkan %bt kandungan tembaga, mangan dan ferum menurun daripada 130 kepada 113°C manakala suhu eutektik meningkat daripada 510 kepada 515°C. Kepekaan pecahan cecair pula berkurangan daripada 0.017 kepada 0.007°C-1 manakala suhu tingkap pemprosesan menurun daripada 26 kepada 24°C. Tindak balas perduaan eutektik pula berlaku antara 30 dan 50% pecahan cecair untuk kesemua kumpulan aloi. Gambarajah fasa digunakan untuk mengetahui fasa sebatian antara logam seperti β-Al5FeSi dan Al2Cu yang terbentuk dalam aloi tersebut. Hasil daripada permodelan termodinamik ini menunjukkan kesesuaian aloi yang dipelbagaikan %bt elemen tembaga, mangan dan ferum digunakan untuk pemprosesan logam separa pepejal