Farazila Yusof

Utilising friction spot joining for dissimilar joint between aluminium alloy (A5052) and polyethylene terephthalate

Abstract The weld strength of thermoplastics with aluminium alloy, such as high density polyethylene and polypropylene sheets, is influenced by friction stir welding parameters. This paper focuses on the preliminary investigation of joining parameter at various levels as well as the mechanical properties of friction spot joining (FSJ) of aluminium alloy (A5052) to polyethylene terephthalate (PET). A number of FSJ experiments were carried out to obtain optimum mechanical properties by adjusting the plunge speed and plunge depth in the ranges of 5–40 mm min−1 and 0·4–0·7 mm respectively, while spindle speed remains constant at 3000 rev min−1. The results indicated that A5052 and PET successfully joined with the aid of frictional heat energy originated from the friction spot welding process. The effect of plunge speed on the joined area and the effect of formation of bubbles at the interface of joints on the shear strength of joint are discussed.

A modified particle swarm optimization for solving the integrated location and inventory control problems in a two-echelon supply chain network

In this study, the design of a two-echelon distribution supply chain network for the seasonal products with multiple vendors (manufacturers) and buyers (retailers), and a set of warehouses for each vendor are considered. The locations of the buyers are known and the capacity of the warehouses is restricted while the buyers purchase different products from the vendors under all unit discount policy. The main objective of this research is to find out the optimal locations of the potential vendors in addition to the quantity ordered (allocation) by the buyers so that the total inventory cost including ordering (transportation), holding and the purchasing costs is minimized. Besides, the distance from the buyers to the vendors is considered as the Euclidean distance. The total budget to buy the products is limited and the production capacity of each vendor is also restricted. To solve the problem, a modified particle swarm optimization (MPSO) algorithm is applied where the results are validated using a genetic algorithm (GA). Finally, some computational examples are generated to assess the algorithms’ performance where MPSO shows a better efficiency in comparison with the GA.

Laser-based Surface Modifications of Aluminum and its Alloys

Aluminum (Al) and its alloys have widespread engineering applications because of their higher strength to weight ratio, ductility, and formability. However, in various applications, mechanical properties such as hardness, corrosion, wear, and fatigue resistance are prerequisite at near surface regions. Such localized modification without affecting the bulk phase can be performed by various surface-engineering approaches including electro-deposition, physical and chemical vapor depositions, thermal spraying, plasma spraying, and organic polymeric coatings. Delamination failure of such coatings from the substrate is often inevitable due to the difference in film-to-substrate elastic modulus associated with the aforementioned processes. Recently, researchers have adopted a new approach of laser surface engineering to modify the near surface regions of metallic substrate by laser beams resulting in superior mechanical properties with the formation of novel microstructures. In this article, the recent developments in the surface modification of Al and its alloy by laser treatment are reviewed. Processing parameters and resulting microstructures of Al and its alloys are briefly summarized, along with their impact on mechanical properties. Finally, this article concludes future research directions.

Toward improved mechanical, tribological, corrosion and in-vitro bioactivity properties of mixed oxide nanotubes on Ti-6Al-7Nb implant using multi-objective PSO.

Recently, the robust optimization and prediction models have been highly noticed in district of surface engineering and coating techniques to obtain the highest possible output values through least trial and error experiments. Besides, due to necessity of finding the optimum value of dependent variables, the multi-objective metaheuristic models have been proposed to optimize various processes. Herein, oriented mixed oxide nanotubular arrays were grown on Ti-6Al-7Nb (Ti67) implant using physical vapor deposition magnetron sputtering (PVDMS) designed by Taguchi and following electrochemical anodization. The obtained adhesion strength and hardness of Ti67/Nb were modeled by particle swarm optimization (PSO) to predict the outputs performance. According to developed models, multi-objective PSO (MOPSO) run aimed at finding PVDMS inputs to maximize current outputs simultaneously. The provided sputtering parameters were applied as validation experiment and resulted in higher adhesion strength and hardness of interfaced layer with Ti67. The as-deposited Nb layer before and after optimization were anodized in fluoride-base electrolyte for 300min. To crystallize the coatings, the anodically grown mixed oxide TiO2-Nb2O5-Al2O3 nanotubes were annealed at 440°C for 30min. From the FESEM observations, the optimized adhesive Nb interlayer led to further homogeneity of mixed nanotube arrays. As a result of this surface modification, the anodized sample after annealing showed the highest mechanical, tribological, corrosion resistant and in-vitro bioactivity properties, where a thick bone-like apatite layer was formed on the mixed oxide nanotubes surface within 10 days immersion in simulated body fluid (SBF) after applied MOPSO. The novel results of this study can be effective in optimizing a variety of the surface properties of the nanostructured implants.

Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn–Ag–Cu/Cu solder joint during different thermal conditions

Abstract Nanocomposite lead-free solders are gaining prominence as replacements for conventional lead-free solders such as Sn–Ag–Cu solder in the electronic packaging industry. They are fabricated by adding nanoparticles such as metallic and ceramic particles into conventional lead-free solder. It is reported that the addition of such nanoparticles could strengthen the solder matrix, refine the intermetallic compounds (IMCs) formed and suppress the growth of IMCs when the joint is subjected to different thermal conditions such as thermal aging and thermal cycling. In this paper, we first review the fundamental studies on the formation and growth of IMCs in lead-free solder joints. Subsequently, we discuss the effect of the addition of nanoparticles on IMC formation and their growth under several thermal conditions. Finally, an outlook on the future growth of research in the fabrication of nanocomposite solder is provided.

Effect of rare earth elements and their oxides on tribo-mechanical performance of laser claddings: A review

Laser cladding is a promising photon-based surface engineering technique broadly utilized for fabricating harder and wear resistant composite coatings. In spite of excellent properties, the practical applications of laser claddings are relatively restricted when compared with well-established coating techniques because of their inherent defects identified as cracks, pores and inclusions. Substantial evidence suggests that the incorporation of an appropriate amount of rare earth in laser claddings can remarkably prevent these defects. Additionally, the presence of rare earth in laser claddings can notably enhance tribo-mechanical properties such as surface hardness, modulus of elasticity, fracture toughness, friction coefficient and wear rate. In this literature review, the effect of rare earth in reducing dilution and cracks susceptibility of laser claddings in addition to microstructural refinement attained was examined. Mechanical and tribological properties of these claddings along with their underlying mechanism were discussed in detail. Finally, this article summarizes current applications of laser claddings based on rare earth and was concluded with future research directions.

Dissimilar friction stir welding between polycarbonate and AA 7075 aluminum alloy

Abstract In this paper, the effects of process parameters, such as the tool rotational and traverse speeds, on temperature evolution and the microstructural and mechanical properties of dissimilar friction stir welding between 3 mm thick AA 7075 aluminum alloy and polycarbonate (PC) plates were investigated. The tool rotational and traverse speeds were varied from 3000 to 3500 rpm and 50 to 150 mm min−1, respectively. The joint fabricated at 3250 rpm and 100 mm min−1 yielded a highest tensile load of 586 N. Microstructural analysis of the stir zone revealed an interlock phenomenon, the transportation of AA 7075 in polycarbonate, and the absence of ceramic-type (carbide, hydride or oxide) compounds. Microhardness (HV) measurement on the weld zone showed an uneven distribution due to the complicated microstructure of the welded joint. The maximum temperatures of 164°C and 66°C were obtained at 3250 rpm and 100 mm min−1 at a distance of 5 mm away from the welding centerline in the AA 7075 and PC side, respectively.

Effect of ultrasonic vibration time on the Cu/Sn-Ag-Cu/Cu joint soldered by low-power-high-frequency ultrasonic-assisted reflow soldering.

Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1.5s of USV, but coarsen when the USV time reached 3s and above. The solder matrix hardness increased when the solder matrix was refined, but decreased when the solder matrix coarsened. The interfacial intermetallic compound (IMC) layer thickness was found to decrease with increasing USV time, except for the USV-treated sample with 1.5s. This is attributed to the insufficient USV time during the reflow stage and consequently accelerated the Cu dissolution at the joint interface during the post-ultrasonic reflow stage. All the USV-treated samples possessed higher shear strength than the control sample due to the USV-induced-degassing effect. The shear strength of the USV-treated sample with 6s was the lowest among the USV-treated samples due to the formation of plate-like Ag3Sn that may act as the crack initiation site.

Laser Composite Surfacing of Ni-WC Coating on AA5083 for Enhancing Tribomechanical Properties

ABSTRACT Laser composite surfacing (LCS) has emerged as an alternative photon-driven manufacturing technology for the fabrication of composite coatings to enhance the tribomechanical properties of various aluminum alloys. The current research presents an analysis on optimization of laser processing parameters for Ni-WC composite coating deposited on AA5083 aluminum alloy in order to improve its tribomechanical properties. To carry out the investigation, Taguchis optimization method using a standard L16 (34) orthogonal array was employed. Thereafter, the results were analyzed using signal-to-noise (S/N) ratio response analysis and Pareto analysis of variance (ANOVA). Finally, confirmation tests with the best parameter combinations obtained in the optimization process were made to demonstrate the progress made. Results showed that the surface hardness (953 Hv) and roughness (0.81 μm) of coated AA5083 samples was enhanced by 9.27 and 13.14%, respectively. The tribological behavior of LCS samples was investigated using a ball-on-plate tribometer against a counterbody of 440c steel. It was revealed that the wear of the Ni-WC-coated samples improved by around 2.5 times. For lower applied loads, the coating exhibited an abrasive wear mode and a reduction in plastic deformation.

Fabrication and Compressive Properties of Low to Medium Porosity Closed-Cell Porous Aluminum Using PMMA Space Holder Technique

In recent years, closed-cell porous Aluminum (Al) has drawn increasing attention, particularly in the applications requiring reduced weight and energy absorption capability such as in the automotive and aerospace industries. In the present work, porous Al with closed-cell structure was successfully fabricated by powder metallurgy technique using PMMA as a space holder. The effects of the amount of PMMA powder on the porosity, density, microstructure and compressive behaviors of the porous specimens were systematically evaluated. The results showed that closed-cell porous Al having different porosities (12%–32%) and densities (1.6478 g/cm3, 1.5125 g/cm3 and 1.305 g/cm3) could be produced by varying the amount of PMMA (20–30 wt %). Meanwhile, the compressive behavior results demonstrated that the plateau stress decreased and the energy absorption capacity increased with increasing amount of PMMA. However, the maximum energy absorption capacity was achieved in the closed-cell porous Al with the addition of 25 wt % PMMA. Therefore, fabrication of closed-cell porous Al using 25 wt % PMMA is considered as the optimal condition in the present study since the resultant closed-cell porous Al possessed good combinations of porosity, density and plateau stress, as well as energy absorption capacity.