Browsing by Author "Zuhailawati H."

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Design of experiment (DOE) study of hydroxyapatite-coated magnesium by cold spray deposition
(2015) Hasniyati M.R.; Zuhailawati H.; Ramakrishnan S.; Dhindaw B.K.; Mohd Noor S.N.F.
In this study, hydroxyapatite powder was sprayed onto pure magnesium plate using a simple modified cold spray process. The effects of process parameters (i.e.standoff distance, surface roughness, substrate, substrate heating temperature and number of spray)were studied using 2k-1 factorial design.Analysis of variant (ANOVA) were used to determine the significant of process parameters on the coating. Thickness of coating, nanohardness and elastic modulus were chosen as the responses for assessing the most significant parameters that affected the hydroxyapatite coated onto pure magnesium plate. HAP particles have found to be bonded well in sample of run 11 while sample of run 4 show poor bonding between HAP particles and magnesium substrate. The effect of individual variables on the response was briefly discussed. � (2015) Trans Tech Publications, Switzerland.
Dry wear behavior of cooling-slope-cast hypoeutectic aluminum alloy
(2016) Thuong N.V.; Zuhailawati H.; Anasyida A.S.; Huy T.D.; Dhindaw B.K.
This study investigated the effect of use of a cooling slope on the microstructure, hardness and wear behavior of Al-7Si-Mg alloy. The Al-7Si-Mg alloy was cast with and without a cooling slope at a pouring temperature of 6408C. Examination with optical and electron microscopes showed that the microstructure of cast samples using the cooling slope comprised fine and globular primary a-Al phase with homogeneous distribution of eutectic phase, while conventionally cast samples featured coarse and dendritic primary a-Al phase. The wear resistance of the cast sample was significantly better with cooling slope casting. The wear mechanism was found to be a combination of adhesion, delamination, oxidation and abrasive wear for both cooling slope- and conventionally cast samples. The wear mechanisms of cast samples both with and without cooling slope are similar and follow Archard's law. The cooling slopecast samples with fine and globular ?-Al phase, high hardness and low specific wear rate (K') showed the highest wear resistance of 10.08 � 10-5 mm3 N-1 m-1. � Carl Hanser Verlag GmbH & Co. KG.
Effect of Initial Microstructure on Properties of Cryorolled Al 5052 Alloy Subjected to Different Annealing Treatment Temperatures
(2018) Anas N.M.; Dhindaw B.K.; Zuhailawati H.; Abdullah T.K.; Anasyida A.S.
Al 5052 alloy sheets were subjected to different pre-annealing temperatures (150, 200, 250, 300, and 350��C) prior to cryorolling. The process resulted in Al 5052 alloys with different initial microstructures. The pre-annealed alloy sheets were compared with a cryorolled sample not subjected to pre-annealing. The thicknesses of the alloy samples after cryorolling was reduced by 30%. The pre-annealed cryorolled samples exhibited low crystallite size, and high lattice strain. Among them, the cryorolled sample pre-annealed at 300��C had the lowest crystallite size, and the highest lattice strain. Changes in initial microstructure of this sample resulted in a significant improvement in its hardness (88�Hv), tensile strength (333�MPa), and corrosion resistance. The sample had the highest corrosion resistance among the cryorolled samples. � 2018, ASM International.
Enhanced Mechanical Properties and Corrosion Behavior of Biodegradable Mg-Zn/HA Composite
(2017) Salleh E.M.; Zuhailawati H.; Ramakrishnan S.; Dhindaw B.K.
Magnesium (Mg) and its alloys have shown potential for use in the biomedical industry due to their excellent biological performance and biodegradability in the bioenvironment. Thus, the aim of the present study was to develop a reliable biodegradable hard tissue substituent. Biodegradable and bioactive Mg-Zinc (Zn) reinforced by hydroxyapatite (HA) composite was prepared using mechanically alloyed Mg-6.5 wt pct Zn and pure HA powders as starting materials. Various HA contents (i.e., 5, 10, 15, and 20 wt pct) were introduced in forming the Mg-Zn/HA composite. The effect of bioactive HA incorporation in biodegradable Mg-6.5 wt pct Zn alloy matrix on mechanical and biodegradation properties as well as microstructural observation was investigated. As measured by the Williamson�Hall formula, the Mg crystallite size of the sintered composites containing 5, 10, 15, and 20 wt pct HA were 36.76, 29.08, 27.93, and 27.31�nm, respectively. According to X-ray diffraction (XRD) analysis, there was no new crystalline phase formed during milling, indicating that no mechanochemical reactions between Mg-Zn alloy and HA occurred. The ?1.70�V shifted significantly toward the passive position of the plain Mg-6.5 wt pct Zn alloy and Mg-Zn/10 wt pct HA composite, which were ?1.50 and ?1.46�V, respectively, indicating that the Mg-Zn/10 wt pct HA composite was least susceptible to corrosion in the bioenvironment. � 2017, The Minerals, Metals & Materials Society and ASM International.
Friction stir processed of 6061-t6 aluminum alloy reinforced with silica from rice husk ash
(2014) Zuhailawati H.; Halmy M.N.; Almanar I.P.; Dhindaw B.K.
This paper presents a development of a composite using friction stir process of AA606-T6 aluminum alloy reinforced with amorphous silica obtained from rice husk ash. The amorphous silica was produced after acid leaching and calcinations at 500�C. The silica powder was placed into a groove that was made in the joining line of AA606-T6 plates prior to friction stir process. Hard silica particles restricted the grain growth of aluminum matrix that contributed to a slight increase in hardness. Hardness decreases in zones under the tool was observed because AA6061-T6 alloy was sensitive to friction heat generated by the tool. Ageing at 200�C increased the hardness of the aluminum in the friction stir process zones. � (2014) Trans Tech Publications, Switzerland.
Hydroxyapatite-coated magnesium-based biodegradable alloy: Cold spray deposition and simulated body fluid studies
(2013) Noorakma A.C.W.; Zuhailawati H.; Aishvarya V.; Dhindaw B.K.
A simple modified cold spray process in which the substrate of AZ51 alloys were preheated to 400 C and sprayed with hydroxyapatite (HAP) using high pressure cold air nozzle spray was designed to get biocompatible coatings of the order of 20-30 ?m thickness. The coatings had an average modulus of 9 GPa. The biodegradation behavior of HAP-coated samples was tested by studying with simulated body fluid (SBF). The coating was characterized by FESEM microanalysis. ICPOES analysis was carried out for the SBF solution to know the change in ion concentrations. Control samples showed no aluminum corrosion but heavy Mg corrosion. On the HAP-coated alloy samples, HAP coatings started dissolving after 1 day but showed signs of regeneration after 10 days of holding. All through the testing period while the HAP coating got eroded, the surface of the sample got deposited with different apatite-like compounds and the phase changed with course from DCPD to ?-TCP and ?-TCMP. The HAP-coated samples clearly improved the biodegradability of Mg alloy, attributed to the dissolution and re-precipitation of apatite showed by the coatings as compared to the control samples. � 2013 ASM International.
Investigation of the microstructure, mechanical and wear properties of AA6061-T6 friction stir weldments with different particulate reinforcements addition
(2019) Abioye T.E.; Zuhailawati H.; Anasyida A.S.; Yahaya S.A.; Dhindaw B.K.
Welding of heat-treated AA6061-T6 often results in mechanical and wear properties deterioration because of the dissolution of the strengthening precipitates at the joint. Enhancement of these properties has been accomplished for non-heat treatable aluminium alloys through the addition of reinforcement particles in the joint. However, its application to AA6061-T6 is scarce. In this work, the microstructure, hardness and wear resistance of AA6061-T6 friction stir welded joints reinforced with SiC, B4C and Al2O3 particles were investigated while the base metal and the unreinforced welded joint were utilised as the control. Aluminium matrix grains refinement which improved with increased particle distribution homogeneity occurred in the entire welded joints. All the reinforced welded joints showed improvements on the unreinforced joint in terms of hardness and wear resistance because of the particles high hardness and substantially increased grain refinement that occurred in the reinforced welded joints. Due to B4C extremely high hardness and homogeneous distribution in the joint, B4C reinforced joint exhibited the highest improvements in hardness (42%) and wear rate (67%) at low-load condition. However, at high-load condition, SiC followed by the Al2O3 reinforced joints showed the least wear rate even lower than the base metal. The matrix hardness significantly influenced the wear performance at low-load but the overall effects of the reinforcement particles were predominant at high-load condition. The reinforcements' additions reduced the wear rate of the welded joint by up to a factor of 1.7 and 1.9 at low and high load conditions respectively. � 2019 The Authors.
Mechanical and degradation behaviour of biodegradable magnesium�zinc/hydroxyapatite composite with different powder mixing techniques
(2019) Mohamad Rodzi S.N.H.; Zuhailawati H.; Dhindaw B.K.
Magnesium-based biomaterials have recently gained great attention as promising candidates for the new generation of biodegradable implants. This study investigated the mechanical performance and biodegradation behaviour of magnesium-zinc/hydroxyapatite (Mg�Zn/HA) composites fabricated by different powder mixing techniques. A single step mixing process involved mechanical alloying or mechanical milling techniques, while double step processing involved a combination of both mechanical alloying and mechanical milling. Optimum mechanical properties of the composite were observed when the powders were prepared using single step processing via mechanical alloying technique. However, Mg�Zn/HA composite fabricated through single step processing via mechanical milling technique was found to have the most desirable low degradation rate coupled with highest bioactivity. The composite achieved the lowest degradation rate of 0.039 � 10?3 mm/year as measured by immersion test and 0.0230 mm/year as measured by electrochemical polarization. Ca:P ratio of the composite also slightly more than enough to aid the initial bone mineralization, that is 1:1.76, as the required Ca:P ratio for initial bone mineralization is between 1:1 and 1:1.67. � 2019
Prediction of compressive strength of biodegradable Mg-Zn/HA composite via response surface methodology and its biodegradation
(2016) Soon L.L.; Zuhailawati H.; Suhaina I.; Dhindaw B.K.
This work aimed to fabricate magnesium zinc/hydroxyapatite (Mg-Zn/HA) composite via powder metallurgy method and to develop a mathematical model to predict the compressive strength of the composite using response surface methodology method. The effect of various mechanical milling parameters, milling speed (200-300 r/min), ball-to-powder weight ratio (5-12.5) and HA content (2.6-10 wt%) on the compressive strength of Mg-Zn/HA composite was investigated. The model shows that high compressive strength of Mg-Zn/HA composite was achieved when the powders were prepared with high milling speed and ball-topowder weight ratio and low HA content. The mathematical model was adequate with error percentage lower than 3.4%. The microstructure of Mg-Zn/HA composite with different process parameters revealed that fine microstructure was observed at high milling speed and ball-to-powder weight ratio while agglomeration of HA was found in composite with 10 wt% HA. The agglomeration of HA led to degradation of interfacial bonding strength between matrix and reinforcement phases and hence decreased the overall compressive strength of Mg-Zn/HA composite. Biodegradation test revealed that sample with higher HA content had more weight gain and there was more formation of hydroxyapatite. Mg-Zn/HA composite with 8 wt% HA was found to be the best candidate for implant application because it had considerable compressive strength and good biodegradation properties. � 2016 The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg.
The role of roller speed on solidification of Al-Mg-Si alloy during twin roll strip casting
(2015) Zuhailawati H.; Yusof M.M.; Anasyida A.S.; Almanar I.P.; Dhindaw B.K.
In the production of aluminum alloy strips for packaging industry twin roll strip casting technique is now being extensively employed. The twin roll caster has advantage of the energy saving, low cost equipment and rapid solidification. The present research aimed to investigate the microstructure and hardness of twin roll strip cast aluminum alloys strips by varying the speed of roller cast. Al-Mg-Si ingot was melt in an induction furnace. Once it melted, the liquid was poured into a crucible attached to a twin roller cast to maintain the liquid temperature at 700�C. Molten alloy was poured in the gap between the copper rollers to produce the strips. The rotational speed of the cast rolls was varied from 60-30 rpm. During this process, the melt solidified to form strips. A specimen of 50 mm length cut from the cast strips was subjected to physical and mechanical characterization. Variation in hardness and microstructure of the produced trip were discussed. � (2015) Trans Tech Publications, Switzerland.