Roslee Ahmad

Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

Influence of cerium on microstructure and solidification of eutectic Al–Si piston alloy

Thermal analysis has become very important in foundry because it aids in studying the effect of additives on eutectic growth temperature and assessing the quality of modifications. This research was performed to investigate the influence of the addition of Ce (0.1–1.0 wt.%) on the eutectic Al–Si–Cu–Mg alloy characteristics of solidification. Field emission scanning electron microscopy (FESEM) and optical microscopy were employed to characterize the alloy microstructure. The main phases studied were the Al–Cu (Al2Cu) and Al–Si phases. The addition of Ce decreased the nucleation and growth temperatures and acted as a refiner for the alloy. The larger amounts of Ce significantly impacted the Si structure: the average Si particle size decreased as the Ce concentration was increased, which led to a finer grain structure. The Ce formed intermetallic compounds with the alloyed elements that had plate- or needle-like structures and that interrupted the modification of Si. The solidification parameters, including the growth and nucleation temperatures, increased with increasing change in the morphology of the Al–Cu phase that were caused by Ce addition.

Solidification, microstructure, and mechanical properties of the as-cast ZRE1 magnesium alloy with different praseodymium contents

The influence of praseodymium (Pr) content on the solidification characteristics, microstructure, and mechanical properties of ZRE1 magnesium (Mg) cast alloy was investigated. The obtained solidification parameters showed that Pr strongly affected the solidification time, leading to refinement of the microstructure of the alloys. When the freezing time was reduced to approximately 52 s, the grain size decreased by 12%. Mg12Zn (Ce,Pr) was formed as a new phase upon the addition of Pr and was detected via X-ray diffraction analysis. The addition of Pr led to a substantial improvement in mechanical properties, which was attributed to the formation of intermetallic compounds; the ultimate tensile strength and yield strength increased by approximately 10% and 13%, respectively. Pr addition also refined the microstructure, and the hardness was recovered. The results herein demonstrate that the mechanical properties of Mg alloys are strongly influenced by their microstructure characteristics, including the grain size, volume fraction, and distribution of intermetallic phases.

Reduction in secondary dendrite arm spacing in cast eutectic Al–Si piston alloys by cerium addition

The effects of Ce on the secondary dendrite arm spacing (SDAS) and mechanical behavior of Al–Si–Cu–Mg alloys were investigated. The reduction of SDAS at different Ce concentrations was evaluated in a directional solidification experiment via computer-aided cooling curve thermal analysis (CA‒CCTA). The results showed that 0.1wt%–1.0wt% Ce addition resulted in a rapid solidification time, Δts, and low solidification temperature, ΔTS, whereas 0.1wt% Ce resulted in a fast solidification time, Δta–Al, of the α-Al phase. Furthermore, Ce addition refined the SDAS, which was reduced to approximately 36%. The mechanical properties of the alloys with and without Ce were investigated using tensile and hardness tests. The quality index (Q) and ultimate tensile strength of (UTS) Al–Si–Cu–Mg alloys significantly improved with the addition of 0.1wt% Ce. Moreover, the base alloy hardness was improved with increasing Ce concentration.

Effect of Elements Cerium and Lanthanum on Eutectic Solidification of Al-Si-Cu near Eutectic Cast Alloy

The properties of Al-Si-Cu cast alloys are strongly affected by eutectic Al-Si and Al-Cu phases. The characteristic parameters of these two phases with additions cerium 1wt % (Ce) and lanthanum1 wt % (La) were investigated in Al-11Si-2Cu near eutectic alloy using computer-aided cooling curve thermal analysis. As a result, the La additive showed the highest (TNAl-Si) while the Ce additive showed very little effect. In addition, the growth temperature (TGAl-Si) is decreased by adding Ce compared to the base alloy and La addition. Additives showed an increase of recalescence magnitude (TRAl-Si). Addition La and Ce increased the nucleation and growth temperature of Al-Cu phase. The microstructure analysis on the silicon morphology showed that 1 wt % La and 1 wt % Ce additions play refiner role in Al-Si-Cu near eutectic alloys. Findings are also confirmed by aspect ratio of eutectic silicon phase.

Surface modification of hypereutectic Al-Si alloy via friction stir process

The surfaces of cast hypereutectic Al-Si-Cu-Ni-La alloy plate was subjected to single pass Friction Stir Processing (FSP) with the aim of decreasing the Si and intermetallic particles size, porosity, and enhancing tensile properties. After FSP, the FS-processed sample shows an improvement in tensile strength value of about 27.5% compared to the as cast base alloy. Optical and scanning electron micrographs indicated that FSP significantly decreases the size of Si, intermetallic particles, and reduced porosity in the alloy, which contributed to the enhancement in tensile properties.

Effect of Mish Metal Cerium Addition on Fluidity of Aluminum Eutectic Silica Alloys - LM6

The evaluation of 0.1 to 1.0% of Ce addition effect on fluidity has been investigated. The fluidity of LM6 has decreased with the Ce addition. The effect of Ce can be shown very clearly with a high amount of 1% wt of Ce. The fluidity length of the composites is shorter than that of the LM6 base material. In spiral mold, the fluidity length is shortened when the weight percentage of Ce content is increased in the base metal LM6. Optical microscope images showed that the 1.0 % of Ce additive led to modification of silica morphology which reduced the fluidity length to 28%. The partial modification of silica can be observed clearly in small amount of Ce but it does not have large affect on the fluidity length.

The Effect of Metallic Addition on Mechanical Property of Aluminum (LM6) Alloy

This article investigates the effects of addition of alloying element on the impact toughness of as-cast aluminum (LM6) alloy. Presence of 0.1 wt.% Cr increases the toughness up to 38%. In fact the sharp tips Fe intermetallics which have needle shape act as stress raisers with a general reduction of the ductility and ultimate tensile strength. On the other hand by increasing the Cr content in the base alloy the size distribution of the compounds becomes more spread. Therefore addition of Cr improves toughness impact by two mechanisms. First eliminating harmful β-intermetallics and second providing microstructure with more spread particles.

The Influence of Metallic Addition on Fluidity of Aluminum (LM6) Alloy

The effect of Cr addition on the fluidity of aluminum (LM6) alloy has been investigated by spiral fluidity test. Presence of 0.1 wt.% Cr decreased fluidity of melt due to formation of sludge. In fact Cr changes the morphology of the intermetallic phase from β-intermetallics less harmful polyhedral morphology (α-intermetallics). The β-phases have largest surface to volume ratio, hence they have the largest interfacial region with the melt and are the most detrimental intermetallic to drop off the fluidity. In Cr-containing alloys the effect of α-phase is less detrimental than β-phase to the fluidity. On the other hand sludge formation and consuming Si and shifts the local chemical composition of the melt to the aluminum side of the phase diagram which has lower fluidity than eutectic and hypereutectic compositions.

The Effect of Vortex well Thickness on Microstructure and Mechanical Properties of Aluminium LM6

Gating system in a casting mold consists of a series of channels and reservoirs designed to feed molten metal to all parts of the mold cavity. The design of the system is the principle means by which the mold designer can control the rate of the metal flow and promote the desirable temperature distribution of cooling that will take place within the filled cavity. This research was conducted to determine the effects of vortex well thickness on the microstructure and mechanical properties of Aluminium LM6 in sand casting process. The experimental results show that increasing the vortex well thickness leads to a significance improvement on the flexural strength of the cast material. In addition, casting defects such as shrinkage porosity and gas porosity would be minimized as the thickness of the vortex well increases.