Rosli Ahmad

Effect of High Cerium and Lanthanum on Impact Toughness of Al-11Si-Cu Eutectic Cast Alloy

The effect of additive elements on impact toughness of Al-11Si-Cu alloy was investigated. The impact test bars were used as impact specimens. The energy of Al-11Si-Cu was improved with Sr modifier addition. The high ability of Ce and La to form large structure intermetallic in Al-Si-Cu will reduce the energy. The RE-intermetallic has an effect on impact analysis, which facilitates to increase the porosity pore.

Drying Comparison of Nonhygroscopic and Hygroscopic Materials

This paper investigates and presents the simulation of drying for hygroscopic and nonhygroscopic materials. This present work used a coupled mathematical model of mass, heat and gas transfer that implemented to finite element method in two dimensional and numerically compute using Skyline solver to capture highly nonlinear transient process. Bound water contribution was taken into account in the drying of hygroscopic materials by incorporating constitutive equation of bound water. The results showed drying process can be divided into three periods named constant rate period (CRP), first falling rate period (FRP1) and second falling rate period (FRP2). Capillary action is dominated during CRP before vapour diffusion takes place in FRP1. Bound water movement is generated by vapour pressure gradient exists that represent hygroscopic material.

Effect of pouring temperature on microstructure properties of Al-Si LM6 Alloy sand casting

In the present paper an experimental investigation on green sand casting of Al-Si cast alloy (LM6) has been conducted. The main objectives of the research were the effect of pouring temperature on microstructure property of green sand casting Al-Si LM6 Alloy. The high quality of The LM6 alloy was investigated by controlling the pouring temperature. The pattern was flat like and pouring was done with four different temperatures 630, 660, 690 and 720Cº. The obtained results showed that the pouring temperature has a significant influence on the quality of green sand casting of LM6 Al-Si alloy. The lower pouring temperature provides finer microstructure with fewer defects such as porosity.

The Influence of Holmium on the Microstructure and Hardness of Mg-Nd-Gd-Zn-Zr Alloys

The influence of holmium on the microstructure and hardness of Mg-Nd-Gd-Zn-Zr alloys were investigated. Conventional casting methods are used to produce the alloys. All the results were characterized by optical microscopy, scanning electron microscope (SEM) and the Vickers hardness test to highlight the influence of holmium addition. The addition of 2.0 wt.% holmium leads to the combination of rare earth elements which formed Mg-Zn-Nd-Ho phase. The results have shown the addition of Ho improved the microstructure and hardness of Mg-Nd-Gd-Zn-Zr alloys. By adding grain size of 2.0 wt.% holmium had reduced by 18.43%, while the volume fraction increased by 7.34%. The Vickers hardness value improved 6.18% due to the grain refine and volume fraction precipitates. The 2.0 wt.% holmium addition showed a positive result in microstructure and hardness value.

Design Element Concept of Die Casting Process

Design Element Concept of die casting process was explored. Direct Differentiation Method (DDM) was employed to calculate the Design Element Sensitivities of die casting process. The mathematical formulation of the DDM method was derived. The results obtained from the DDM method was compared with Finite Difference Method (FDM) and the results showed closed agreement.

Effect of Yttrium Addition on Microstructure and Hardness of Cast EV31A Magnesium Alloy

The effect of the rare earth (RE) element Y on the microstructure and hardness of (Mg–0.5Zn–0.5Zr–2.8Nd –1.5Gd) wt% Mg alloy investigated. 1 wt. % Y was added and compared with the base alloy. The microstructure results show the refinement of the grain by the addition of Y and the grains became smaller about 31.8 % and the volume fraction was increases 11.1% %, which led to the increment of hardness from 48.33 HV (as-cast EV31A) to 53.71 HV (as-cast EV31A +1 Y). Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) results showed that the base alloy mainly contained α-Mg matrix and Mg-(Nd, Gd) as a second phase crystallized along the grain boundaries and addition of (Y) yttrium resulted in the formation of the new phase, Mg-Zn-Y-phase was found as a new ternary phase, where Y combined with the original second phase.

Fabrication of AA6061-0/RHA Surface Composite via Friction Stir Processing

Friction stir processing is a novel process evolved to fabricate surface metal matrix composites. Rice husk ash (RHA) is an agro-industrial waste and by product of rice husk. The feasibility of incorporating RHA powder into aluminium alloy AA6061-0 as reinforcement particles to make surface matrix composite via FSP is reported in this paper. The optical micrographs revealed a homogeneous distribution of RHA particles which were well bonded with the matrix in both first and fourth-passes of the FSP due to mechanical stirring. Microhardness of the stir zone SZ with the RHA particles of I-pass increased to about 106 HV, 40% higher than that of the base material 66 HV by dispersed RHA particles.

The Effect of Microstructure and Mechanical Properties of Aluminium Aa6061 before and after Heat Treatment Using TIG

This work studies the effect of a post-weld heat treatment (PWHT) on the mechanical and microstructure properties of an AA6061 sample welded using Tungsten Inert Gas (TIG) method. TIG method is comparatively flexible and has good economy. The welded samples were divided into as-welded and PWHTs samples. The PWHTs samples were solution heat treatment, water quenching and artificial aging. Both welded samples were cut according to the ASTM E8M-04 standard to obtain the tensile strength and the elongation of the joints. The failure pattern of the tensile tested specimens was analysed using scanning electron microscopy (SEM). A Vickers microhardness testing machine was used to measure the hardness across the joints. From the results, the PWHTs were able to enhance the mechanical properties and microstructure characteristics of the AA6061 joints welded by the TIG method.

Design sensitivity analysis of squeeze casting process

Optimisation studies have explored the application of a number of strategies. These include principally gradient methods and genetic algorithms. The former require the calculation of gradients that link design parameters with system response and combined with optimisation routines, they are used to find the best design according to a specified objective function and design variable constraints. Although they require gradient calculation, they are less computationally demanding, but are restricted in their search field. Gradient-based optimisation is one of the most popular strategies in tackling optimisation in engineering design problems.