Khairel Rafezi Ahmad

Effect of friction stir processing on the microstructure and hardness of an aluminum-zinc-magnesium-copper alloy with nickel additives

The main object of this study is to investigate the effect of friction stir processing (FSP) on the microstructure and hardness of Al-Zn-Mg-Cu alloys that were produced via casting with the addition of 5 wt % nickel. Furthermore, a single-pass FSP with a rotational speed of 1500 rpm and a traveling speed of 40 mm/min was performed on the alloys. The FSP-treated cast alloys were homogenized, aged at 120°C for 24 h, retrogressed at 180°C for 30 min, and then re-aged at 120°C for 24 h. Microstructural evaluations via optical microscopy and scanning electron microscopy, as well as with energy dispersive X-ray spectroscopy were conducted. In addition, X-ray diffraction analysis was performed to detect the intermetallics and phases of the Al-Zn-Mg-Cu-Ni alloys. Before FSP, the microstructural observations indicated the presence of coarse Ni dispersed particles with a precipitate phase within the matrix. After FSP treatment, the grain refinement led to the uniform space distribution of Ni dispersed particles in the stir zone. The Vickers hardness values for the Al-Zn-Mg-Cu-Ni alloy increased after age tempering at T6 and retrogression and re-aging (RRA) treatment because of the increased precipitation and particles dispersity. The hardness of the Al-Zn-Mg-Cu-Ni alloy was enhanced after FSP and a series of heat treatments, especially the RRA process, because of the stirring action of the FSP tool, the grain refinement, the appearance of additional precipitates, and the refinement of dispersed Ni particles.

Wettability, Electrical and Mechanical Properties of 99.3Sn-0.7Cu/Si3N4 Novel Lead-Free Nanocomposite Solder

A nanocomposite solder alloy with 99.3Sn-0.7Cu base alloy was successfully fabricated using the powder metallurgy route which consists of blending, compaction and sintering. Varying amount of nano size silicon nitride particulates were introduced as reinforcements to obtain a novel lead-free nanocomposite solder alloy. Following fabrication, the sintered nanocomposite solder were cut into thin solder disc and were analyzed in terms of their wettability, electrical and mechanical properties. Wettability, electrical and mechanical properties of the nanocomposite solder were compared to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder which were fabricated with the same method using powder metallurgy route. Wettability property of the nanocomposite solder was found to be in the accepted range with wettability angle below 45° similar to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder. Besides wettability, the results of electrical and mechanical properties analysis showed that additions of nano size Si3N4 had enhanced the strength and electrical conductivity of nanocomposite solder comparing to 99.3Sn-0.7Cu and 96.3Sn-3.0Ag-0.5Cu lead-free solder.

The Influence of Nickel and Tin Additives on the Microstructural and Mechanical Properties of Al-Zn-Mg-Cu Alloys

The effects of nickel and nickel combined tin additions on mechanical properties and microstructural evolutions of aluminum-zinc-magnesium-copper alloys were investigated. Aluminum alloys containing Ni and Sn additives were homogenized at different temperatures conditions and then aged at 120°C for 24 h (T6) and retrogressed at 180°C for 30 min and then reaged at 120°C for 24 h (RRA). Comparison of the ultimate tensile strength (UTS) of as-quenched Al-Zn-Mg-Cu-Ni and Al-Zn-Mg-Cu-Ni-Sn alloys with that of similar alloys which underwent aging treatment at T6 temper showed that gains in tensile strengths by 385 MPa and 370 MPa were attained, respectively. These improvements are attributed to the precipitation hardening effects of the alloying element within the base alloy and the formation of nickel/tin-rich dispersoid compounds. These intermetallic compounds retard the grain growth, lead to grain refinement, and result in further strengthening effects. The outcomes of the retrogression and reaging processes which were carried on aluminum alloys indicate that the mechanical strength and Vickers hardness have been enhanced much better than under the aging at T6 temper.

Characterization of Cuprous Oxide Thin Films Prepared by Sol-Gel Spin Coating Technique with Different Additives

Cuprous oxide (Cu2O) thin films were formed onto indium tin oxide (ITO) coated glass substrate by sol-gel spin coating technique using different additives namely polyethylene glycol and ethylene glycol. It was found that the organic additives added had an important influenced on the formation mechanism of Cu2O films and lead to different microstructures and optical properties. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and ultraviolet-visible spectroscopy (UV-Vis). Based on the FESEM micrographs the grain size of film prepared by polyethylene glycol has smallest grain of about 83 nm with irregular shape. The highest optical absorbance film was obtained by the addition of polyethylene glycol.

The Effect of Microalloying of Nickel, RRA Treatment on Microstructure and Mechanical Properties for High Strength Aluminum Alloy

High strength aluminum alloys Al-Zn-Mg-Cu-(0.1) Ni produced by semi-direct chill casting process were homogenized at different conditions then conducted heat treatment process which comprised pre-aging at 120°C for 24 h, retrogression at 180°C for 30 min, and then re-aging at 120°C for 24 h. Microstructural studies showed that add Ni (0.1 wt %) to the alloy will be forming Ni-rich phases such as AlCuNi, AlNi, AlNiFe and AlMgNi which provide a dispersive strengthening affected in the solid-solution and the subsequent heat treatments. The results showed that by this three-step process of heat treatments, the mechanical properties of aluminum alloys Al-Zn-Mg-Cu-(0.1) Ni were substantially improved. The highest attain for the ultimate tensile strength and Vickers hardness for the alloy sample after applied the retrogression and reaging process is about 545 MPa and 237 HV respectively.

Effect of Heat Treatment on Microstructure, Hardness and Wear of Aluminum Alloy 332

This paper describes a study on the effects of heat treatment on the microstructure, hardness and wear of aluminum alloys 332 (AlSi9Cu3Mg). The solution treatment was performed at 500°C for 5 hours and then quenched in water at room temperature. Aging was performed at 170°C for 2 hours. The findings revealed that after a full heat treatment, the structure of the eutectic silicon formed toward fragmentation and spheroidization, and the silicon particles became coarse (look-like rounded). Hard intermetallic compound (Mg2Si) appeared on the microstructure after the aging treatment completed. Compared to the as-cast, the hardness of the alloys has improved to 44.84%, and the wear rate of the solution treatment had decreased to 26% while the aging treatment showed a deterioration of 79.42%. The study concludes that aging treatment improves the hardness of AA332 alloys and enhanced the wear resistance of the substance.

Electrochemical Measurement of PBS Using Cyclic Voltammetry and AAO Fabricated at Ambient Temperature and Low Potential

Anodic aluminium oxide fabricated at ambient temperature and low potential in phosphoric acid electrolyte was used as the working electrode for the electrochemical measurement of phosphate buffer saline under different pH conditions using the cyclic voltammetry tool. We investigate the reversibility of the electrochemical reaction as a redox reaction from the cyclic graphs that were obtained. We observed that the ratio of the peak current passed at both the reduction and oxidation when measured was very close to unity in all the pH but except one which produced a none reversible reaction with a non cyclic graph. The peak potential for both reduction and oxidation reactions using phosphate buffer saline as the analyte under different pH of 3, 5, 7, and 9 was also obtained.

The properties of aluminum alloys containing nickel, produced using powder metallurgy method

In this paper, the effects of nickel on the microstructure and mechanical properties of experimental an Al-Zn-Mg-Cu PM alloys under the impacts of the retrogression and re-aging treatment was investigated. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered samples subjected to the homogenizing condition at 470°C for 1.5 hours then aging at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Characterization’s results indicate that the microstructures of an Al-Zn-Mg-Cu-Ni PM alloys presented an intermetallics compound in the aluminum’s matrix, identified as the AlNi and Al3Ni2 phases besides the MgZn and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers’s hardness and dinsifications properties of the alloys.

Effect of Heat Treatment on Hardness Behavior of AZ91 and AZ91 Reinforced Carbon Nanotube

In the present work the effect of heat treatment on the hardness behavior of AZ91 and AZ91 reinforced carbon nanotube were investigated under FESEM, Xrd and Rockwell hardness tester. Cnt was embedded homogenously into the matrix due to successfully mechanical alloying using planetary milling. Kinetic precipitation of β-phase (Mg17Al12) also reveal in the X-ray diffraction pattern. Meanwhile, the artificial aged nanocomposite found decreased in hardness, compare to monolithic has higher value form early aged until 36 hours aging.

Roselle Blend Film Sensor (RBFS) for Detecting Fertilizer Concentration of Grape Tree

A Roselle blend chitosan film sensor (RBFS) with different concentration of roselle has been developed. Electrochemical deposition has been chosen as an efficient technique for the fabrication of RBFS. RBFS with the concentration of 20cc of roselle has a stable value to detect the different concentration of fertilizer ranging from 0 ppm until 60 ppm. The type of fertilizer used in this testing was magnesium sulphate. The electrical laboratory testing result of the RBFS exposed to de-ionised water (DIW) showed the highest response with the value ~94%. The highest response value of RBFS exposed to magnesium sulphate with the concentration of 10 ppm was ~66%. The lowest response value of RBFS exposed to magnesium sulphate with the concentration of 60 ppm was ~30%. The results have been proven that RBFS is able to differentiate the concentration of fertilizer. The RBFS fulfils all the reliable sensing properties which include excellent response time, stability, repeatability, recovery, and selectivity. The morphological surfaces of RBFS were observed with SEM and chemical interactions between roselle blend chitosan were explained using FTIR spectra results. SEM image of RBFS showed the film surface was compact and the roselle was well distributed within the chitosan.