Zuhailawati Hussain

Effect of Milling Speed on Properties of Fe-NbC Composite Prepared by Mechanical Alloying

Nowadays, mechanical alloy (MA) method has turned up as one of a new and applicable method for metal matrix composite fabrication due to some advantages such as the ability to form nanocrystalline structure with improved properties. In this work, different milling speed of MA process (100, 200, 300 and 400 rpm) was performed on Fe-17.21wt%Nb-2.23wt%C with milling duration of 10 hours. The mixture was pressed and sintered at 1300oC into a pellet form. Investigation by X-ray diffraction, measurement of hardness and density were carried out. High milling speed resulted on crystalline-to-amorphous transition of XRD peaks of Fe and NbC phases. Different level of MA at different speed also produced fine NbC particles and strain hardening which resulted in increase value of hardness. The presence of pores, particularly in the composite with high milling speed, decreased the density of Fe-NbC composite.

Characterization of Tantalum Carbide Reinforced Copper Composite Developed Using Mechanical Alloying

The effects of the consolidation pressure on the properties of novel Cu-15vol% TaC composite was investigated. The copper-based composite has been prepared using a high energy planetary mill via in-situ route. A mixture of copper, tantalum and graphite powder was mechanically alloyed for milling time of 8 hours at speed of 400 rpm. The as-milled powder was consolidated by cold pressing under various pressure (i.e. 100, 200, 300 and 400 MPa) at room temperature and sintered in argon atmosphere at 900 °C for an hour. TaC phase was formed in copper matrix after sintering process. An increase in consolidation pressure resulted in an increase in hardness, electrical conductivity and density of the composites. The changes of bulk properties of the in-situ Cu-TaC composite were correlated to the formation of TaC phase and a reduction of porosity which led to an increasing in densification.

Heating Rate Effects on Properties of Powder Metallurgy Fe-Cr-Al2O3 Composites

The aim of this study is to determine the optimum heating rate in fabricating Fe-Cr-Al2O3 composites by powder metallurgy methods. The Fe-based composites reinforced with ceramics are widely used due to their high strength, hardness and wear resistance. Among steps in powder metallurgy methods are mixing, compaction and sintering. Sintering is a very important step due to its ability to evolve microstructural features that govern the end properties. Sintering of green compacts made of iron powder mixture must be performed in vacuum or in a reducing atmosphere because water-atomised iron powder particles are oxidized on the surface and in this way some deoxidation reaction can occur during sintering. The heating process up to sintering temperature, plays a major role, the major proportion of densification occurs during the heating process. The composites produced were subjected to the following tests: densification, Vickers micro hardness, microstructure using SEM and X-ray diffraction analysis. From this investigation, to achieve higher densification and hardness the optimal heating rate is 10°C/minute. X-Ray Diffraction study showed that the fabrication of the composites does not lead to any compositional changes of the matrix phase and the reinforcing phase.

Formation of Titanium Carbide Reinforced Copper Matrix Composite by In Situ Processing

Composite materials with copper matrix and ceramic particle reinforcements provide basis for producing relatively high hardness and electrical conductivity materials. Most of the work on copper-based composites has involved transition metal carbide reinforcement, which is introduced in the copper matrix through a powder metallurgy (P/M) route. TiC particle is one of the interesting candidates for the reinforcement of the Cu composite. This is because of its high melting point, high hardness, good oxidation and corrosion resistance combined with good electrical and thermal conductivity. In this study, in situ prepared copper-titanium carbide using high energy ball milling was addressed. Cu-Ti-C mixture powder was mechanically alloyed by high energy ball milling at 400 rpm speed for 4 hours to investigate the formation of TiC phase during milling. Then, MA was continued for 5, 20, 40,60 and 80 hours in order to determine the formation of titanium carbide phase by milling time. Then the as-milled powders were compacted at 400 MPa and sintered at 900°C for one hour. As-milled powder was characterized by x-ray diffraction for phase identification. From the XRD result, TiC peaks were found at 35.9˚, 41.7˚and 60.4˚.

Characteristic of low temperature of Bi-In-Sn solder alloy

Due to the increase in the use of electronics devices within the industry, the usage of solder connections has increased. These is a concern that lead within the electronic products is considered toxic because lead has potential for leaching from landfills onto water sources and becoming a hazard to human health and surrounding environment. For this reason, replacing Sn-37Pb to free solder with low melting temperature is one of the most important issues in electronic industry. This is due to a demand on low temperature for interconnection and polymer based part component such as LCD display functionality availability at low temperature apply. In this paper, Bi-In-Sn system alloy was investigated as a potential candidate replacing Sn-37Pb. This study covers on solder characteristic such as melting temperature, thermal expansion and microstructure. Bi-In-Sn was prepared and melted in crucible. Solder was cleaned mechanical and chemical before characterized. DSC shows that, Bi-In-Sn system alloy give low melting temperature in range of 65-100°C. The addition of In to Bi-Sn system alloy lowered the melting temperature compared than Sn-37Pb. Lowest melting temperature ensures that the solder melts, forms a joint with the substrates, and re-solidifies within the shortest possible process time. From thermal expansion analysis, it was found that Bi-In-Sn gives good expansion properties to avoid mismatch between Cu pads and solder itself. EDX analysis indicated that, there are two obvious regions in Bi-In-Sn system alloy microstructure. Bright colour refers to BiIn rich phase region and dark colour refers to Sn rich phase region. BiIn rich phase region is higher compared to Sn rich phase in solder give good properties in terms of ductility.

Radon measurements in and around a radiation research laboratory

Abstract Radon was measured in different workshops of research laboratories and residential premises around them and in Islamabad. CR-39 and CN-85 polymeric track detectors were used for this purpose. The radon concentration in various workshops did not prove, in general to have any dependence upon the type of work done in these workshops. The difference in the ventilated and non ventilated residential houses was, however significant.

Influence of binder in iron matrix composites

The ability to use iron and its alloys as the matrix material in composite systems is of great importance because it is the most widely used metallic material with a variety of commercially available steel grades [1]. The aim of this study is to investigate the influence of binder in particulate iron based metal matrix composites. There are four types of binder that were used in this study; Stearic Acid, Gummi Arabisch, Polyvinyl alcohol 15000 MW and Polyvinyl alcohol 22000 MW. Six different weight percentage of each binder was prepared to produce the composite materials using powder metallurgy (P/M) route; consists of dry mixing, uniaxially compacting at 750 MPa and vacuum sintering at 1100° C for two hours. Their characterization included a study of density, porosity, hardness and microstructure. Results indicate that MMC was affected by the binder and stearic acid as a binder produced better properties of the composite.

Optimization Processing Parameter of 6061-T6 Alloy Friction Stir Welded Using Taguchi Technique

Taguchi approach was applied to evaluate the processing parameter to determine the most influential control factors which will yield better tensile strength of friction stir welded joint of 6061-T6 aluminium alloy. The processing parameters involved are tool shoulder diameter, in mm (18 ,20, 22), tool rotational speed, in rpm (410, 865, 1140), and feed rate, in mm/min (22, 32, 45). Taguchi parametric design and optimization approach was used. Through the Taguchi parametric design approach, the optimum levels of process parameters were determined. The results indicate that the shoulder size, rotational speed, and feed rate are the significant parameters influencing the tensile strength and hardness of the joint. The predicted optimal values of tensile strength 6061-T6 aluminium alloy is 321.16 MPa. The results was confirmed by further experiments, where the experimented values for tensile strength is 301.28 MPa.

Experimental Studies on the Effects of Tin on the Densification of W-Brass Composites

The effects of 1% tin (Sn) addition on the densification of pre-alloyed and pre-mixed W-brass composites were carried out. The green compacts were produced with the pressure of 350MPa and sintered at the temperature of 800°C, 920°C and 1000°C. The Sn addition is aimed at inhibiting the dezincification (selective removal of zinc from an alloy) of the brass component by the elimination of pores and enhances densification. The hardness of the composites increased with increase in temperature, the densification was low at both temperatures while the electrical conductivity remains constant as a result of constant composition in both pre-alloyed and pre-mixed composites. The microstructures revealed pores, which might be as a result of zinc evaporation.

Ageing Characteristics of Equal Channel Angular Pressed Al-Mg-Si Alloy

This study investigated the effect of severe plastic deformation (SPD) and artificial ageing treatment on mechanical properties of cast Al-Mg-Si alloy. 6061-T6 aluminum alloy was remelted and casted into a rod of 13mm in diameter and 60mm in length. The rod samples were then subjected to equal channel angular pressing (ECAP) for SPD process, up to 2 passes, through Bc route. Cast and ECAPed samples were solution heat treated at 530 °C, quenched in water and held at 180 °C at various ageing time to determine the effect of artificial ageing. Cast alloy consisted of α phase grains that were surrounded by Mg2Si particles locating at the grain boundaries. The hardness increased with accumulative applied strain by 2-pass ECAP process with the value of 99.4 Hv. For heat treated samples, maximum hardness was achieved after 5-hour ageing.