Grain refinement of Al–Zn–Mg alloy during equal channel angular pressing (ECAP)

Locally produced Al–Zn–Mg alloy was subjected to severe plastic deformation through Equal Channel Angular Pressing (ECAP) technique at temperatures of 150 °C and 200 °C. Rectangular thick-walled medium carbon steel die (σc = 450Mpa, σy = 176Mpa) with an L-shaped channel of uniform configuration to provide the pressing chamber was used. Four ECAP passes were imposed consecutively on set of samples for 150 °C and 200 °C temperatures, and characterized with optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). The phases were identified by X-ray diffraction (XRD) using monochromatic Cu Kα radiation, while vickers’ microhardness and tensile tests were performed for mechanical properties examination. Optical micrographs showed no tangible precipitation in the as cast samples with reduced grain width and deformation bands but at high temperatures of 150 °C and 200 °C, precipitation was promoted as a result of slipping systems activation. SEM images of the as-cast alloy exhibits dendrites of 250 ± 20 μm in size with η′ phase (MgZn2) precipitates in the inter-dendritic regions. For 150 °C ECAP temperature, a significant refinement was achieved as the passes increased with sub-grain development within the boundary and the precipitate observed has a grain size of 35 ± 15 μm, 25 ± 10 μm, 15 ± 8 μm and 8 ± 6 μm for first, second, third and fourth passes respectively. However, grain sizes of 85 ± 15 μm, 50 ± 10 μm, 30 ± 8 μm and 10 ± 5 μm for first, second, third and fourth passes were observed for 200 °C ECAP temperature. XRD results showed peaks for aluminum and other phases in as-cast condition with precipitates growth in the alloy after the first pass, identified as metastable η′ phase. As the number of ECAP passes increases, η′ peaks moved towards the equilibrium η phase confirming the transformation of η′ phase to stable η phase. The microhardness, Ultimate tensile strength (UTS) and the yield strength of Al–Zn–Mg alloy in different conditions of 150 °C and 200 °C respectively also increased with increase in the number of ECAP passes. This is due to increase in dislocation density, work hardening and grain refinement during ECAP process

Evaluation of the mechanical properties and corrosion behaviour of coconut shell ash reinforced aluminium (6063) alloy composites

Aluminium 6063/Coconut shell ash (CSAp) composites having 3-12 weight percent (wt%) coconut shell ash were fabricated by double stir-casting method. The microstructure, ultimate tensile strength, hardness values, density and corrosion behaviour in 0.3M H2SO4 and 3.5wt% NaCl solution of the composites were evaluated. The density of the composites exhibit a linear and proportional decreased as the percentage of coconut shell ash increases in the aluminium alloy. It implies that composites with lower weight component can be produced by adding CSAp. The microstructural analysis showed uniform distribution of coconut shell ash particles in the aluminium alloy matrix. Significant improvement in hardness and ultimate tensile strength values was noticeable as the wt% of the coconut shell ash increased in the alloy, although this occur at the expense of ductility of the composites as the modulus of elasticity of the composites decreases as the percentage of CSAp increases. Hence, this work has established that incorporation of coconut shell particles in aluminum matrix can lead to the production of low cost aluminum composites with improved hardness and tensile strength values. Keywords Coconut shell; Composite; Matrix; Aluminium 6063; Stir casting; Corrosion; Mechanical propertie

Mechanical and Water Absorption Properties of Alkaline Treated Coconut (cocosnucifera) and Sponge (acanthus montanus) Fibers Reinforced Polypropylene Composites

Abstract Natural fiber reinforced polymer composites have raised great attention and interest among researchers in recent years due to the consideration of developing an environmentally friendly and recyclable materials. In this research, the effect of alkaline treatment on the mechanical and water absorption properties of polymer composites developed from coconut and sponge fibers was investigated. The selected fibers were extracted by mechanical decortications and then cut into 10 mm length using scissors. The fibers were chemically treated with KOH in a shaker water bath before dispersing them randomly in polypropylene (PP) matrix. Composites with 2, 4, 6, 8, 10 wt% fibers were developed by compression molding. Tensile and flexural properties were evaluated using universal testing machine while water absorption test was carried out on the samples for 7 days. The research outcomes show that alkaline treatment of the fibers improved the flexural, tensile and water repellant properties of the developed composites

Mechanical properties and water absorption behaviour of treated pineapple leaf fibre reinforced polyester matrix composites...

Investigations were carried out to study the effect of treated pineapple leaf fibre (PALF) on the mechanical properties and water absorption behaviour of reinforced polyester composites. PALF was extracted from pineapple plant using wet retting method. Chemical treatment was carried out on it to hinder water content and enhances good adhesion between fibre and matrix. Both the matrix and the fibre were compounded using hand lay-up method at room temperature. The samples were prepared for tensile test, flexural test, hardness test and water absorption test. It was observed that as the fibre content increases within the matrix, there is corresponding increase in the ultimate tensile strength and modulus of elasticity while there was decrease in the elongation at break. Flexural strength, flexural modulus and hardness properties of the developed composites increase linearly from 10 wt% to 30 wt% fibre loading and begin to decrease from 40 wt% fibre loading. The results of the water absorption test showed that the amount of water absorbed by the composite increased with increase in fibre loading

Abrasion Resistance and Water Absorption Characteristics of Ti-HAp Hybrid Reinforced Polyetheretherketone Biocomposites

The influence of abrasion on biomedical implant in human body is a constant cause of pain, discomfort and sometimes a repeat of surgery as a result of the complications from the effects of wear on the implants and the negative consequences of the resultant abrasive particles on the surrounding tissue and bodily environment. To alleviate this, a titanium-hydroxyapatite hybrid reinforced polyetheretherketone (PEEK) biocomposite material was developed, characterized and tested. X-Ray Diffraction characterization revealed that the calcined eggshell was composed mainly of lime and portlandite. The calcined eggshell was then used in the synthesis of hydroxyapatite powder (HAp) with characteristic bands confirmed by FTIR spectroscopic analysis. Biocomposites were developed from the blend of titanium and hydroxyapatite powders in varying proportions as reinforcements in PEEK matrix. The developed composites and control sample were subjected to abrasion and water absorption tests from where it was revealed that biocomposite sample reinforced with 10 wt.% orthophosphoric acid synthesized eggshell possess optimum abrasion resistance with a wear index of 0.20 mg/cycle with an acceptable level of water absorption next to the unreinforced polyetheretherketone over a period of 35 days

Tensile, Flexural, and Morphological Properties of Jute/Oil Palm Pressed Fruit Fibers Reinforced High Density Polyethylene Hybrid Composites

The incorporation of materials that were formally regarded as agricultural wastes into polymeric matrix has drawn the attention of many researchers in recent years. This research focused on reinforcing high-density polyethylene (HDPE) matrix with treated jute fiber (JF)/oil palm pressed fruit fibers (OPPFF) at varying weight proportions. JF and OPPFF were cut to 2.5 mm length and were chemically treated thereafter with 1 M and 1.5 M sodium hydroxide solution respectively. The composites were produced using the compression molding technique. The morphological characterization of the fibers and composites for untreated and treated samples was studied with the aid of a scanning electron microscope (SEM). Tensile and flexural properties of the produced composite samples were also determined. From the result, the surface morphology of the fiber after treatment showed that there was obvious exposure of the fiber surface and removal of impurities as this influenced the microstructure of the composites and in turn the tensile and flexural properties. Hence, it was observed that 20 wt.% treated jute fiber addition shows the most significant enhancements in terms of tensile and flexural properties. The study exposed the effect of surface modification of JF/OPPF hybridization on HDPE matrix composite