New Al–AlN composites fabricated by squeeze casting: interfacial phenomena (original) (raw)
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Journal of Materials Science, 2010
The squeeze casting process was used to fabricate Al2O3sf/AZ91D magnesium matrix composites before thixoforging. The microstructural evolution process in Al2O3sf/AZ91D was investigated during partial remelting. Tensile mechanical properties of thixoforged automotive component were determined and compared with those of squeeze casting formed composites. The results show that the microstructural evolution during partial remelting exhibited four stages: the formation of liquid, structural fragmentation, the spheroidization of solid particles, and final coarsening. As the holding time increases, the size of solid particles decreases initially and then increases. However, the size of solid particles decreases monotonously as the temperature increases. Increasing holding time or temperature promotes the degree of spheroidization. It is also shown that the cylindrical feedstock of the Al2O3sf/AZ91D composites can be thixoforged in one step into intricate shapes in the semi-solid state. The tensile tests indicate that the yield strength and ultimate tensile strength for Al2O3sf/AZ91D thixoforged from starting material fabricated by squeeze casting and partial remelting are better than those of Al2O3sf/AZ91D fabricated by squeeze casting. This research confirms that thixoforging is a practical method for the near net shape forming of magnesium matrix composites.
Al alloys were infiltrated into Al 2 O 3 preforms in N 2 and N 2 -2% H 2 gas mixture in the temperature regime of 900-1200°C. The kinetics of nitridation during infiltration were continuously monitored by recording weight gained during infiltration of the preform. The weight gains that are attributed to the formation of AlN in the matrix were observed to increase with processing temperature. In addition, higher weight gains were recorded in N 2 -H 2 as compared to in N 2 atmosphere. Analysis of the composites indicates that controlled matrices of AlN/Al can be formed by selection of appropriate process parameters viz. temperature and atmosphere. Based on this study it has been demonstrated that net shaped metal matrix composites (MMCs), with varying amounts of AlN in the matrix can be fabricated by infiltrating alumina preforms at 900-1000°C in commercial nitrogen. By controlling the preform characteristics, it is possible to fabricate composites with significant variation in microstructural scale, and consequently matrix hardness and elastic modulus. 13], the molten Al-alloy reacts with the ambient atmosphere (air, oxygen or nitrogen) to form Al 2 O 3 /Al or AlN/Al composites with an interpenetrating microstructure. Al 2 O 3 /Al composites grown freely and into SiC, Al 2 O 3 preforms by directed melt oxidation have been well investigated and documented . However, similar studies on AlN/Al composites formed by nitridation of Al-Mg and Al-Sr based alloys are relatively fewer. Creber et al. and Aghajanian et al. initially reported the pressureless infiltration of Al-Mg alloys into particles of Al 2 O 3 , SiC, TiB 2 etc. over a range of temperature. They assessed the critical 2
In-situ Synthesis of AlN/Mg Matrix Composites
Magnesium matrix composites with A1N reinforcements are potential engineering materials for automobile and aerospace applications. Attractive properties of A1N include high thermal conductivity and hardness. AlN-reinforced Mg composites have been synthesized by in-situ reaction using pure Al and AZ31B and SÍ3N4 powder as raw materials. Microstructures containing 15 vol.% A1N were obtained by heating the raw materials at 770°C for one hour under argon atmosphere. Composite microstructures were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy. Final microstructures consisted of A1N particles 1-5 micron in size that were distributed within the Mg alloy matrix.
IOP Conference Series: Materials Science and Engineering
Steel is used because of its high strength and toughness, but it has high density, therefore lighter material with comparable toughness is developed. One alternative is aluminum matrix composite with zirconia (ZrO 2) as the reinforcement with high fracture toughness. Al-9Zn-6Mg-3Si (wt. %) composites were developed with addition of 2.5, 5, and 7.5 vol. % ZrO 2 through squeeze casting. To improve toughness, the composite was solution treated at 450 o C for 1 h, then aged at 200 o C for 1 h. Materials characterization included Optical Emission Spectroscopy (OES), Rockwell B hardness testing, impact testing, fractography analysis, microstructure analysis using Optical microscope (OM) and Scanning Electron Microscope (SEM) / Energy Dispersive X-Ray Spectroscopy (EDS), as well as X-Ray Fluorescence (XRF). The results showed that the more ZrO 2 particles, the higher porosity and the lower the hardness and the impact values, both in as-cast condition and after ageing at 200 o C at 1 h.
2011
This research tends to study the effect of change in volume fraction of alpha phase alumina on mechanical properties of a metal matrix composite specimens contain (AlαAl2O3). Specimens were prepared with the following volume fractions (10, 15, 20, 25, 30, 35, 40, and 45). Then effectof this change on hardness, maximum stress and strain, Young’s modulus, impactand wear resistance has been studied. Results of testing showed that while hardness, maximum stress, Young’s modulus, and impact strength increased markedly with volume fraction of alumina, wear rate, and maximum strain decreased with increasing of volume fraction.
Microstructure and mechanical properties of Al-Al 2 O 3 -MgO cast particulate comp
J Mater Sci, 1987
This study focused on the effects of ageing for various time at 175 • C before hot rolling on microstructure and mechanical properties of AZ80 magnesium alloys. The amount of γ-Mg 17 Al 12 increased in line with ageing time and during the rolling process could facilitate the fine grains and sub-grains, which resulted in an inhomogeneous or bimodal microstructure, and weakening basal-type texture intensity or occurrence of double-peak texture. However, a larger quantity of γ-Mg 17 Al 12 distributed on the matrix in the alloy aged for 240 min, or the precipitates decorating the grain boundaries in the alloy aged for 75 min, were detrimental to the mechanical properties, and lower ultimate tensile strength with elongation were obtained in the two alloys as a result. When the alloy was aged for 200 min, it showed an optimum mechanical property with its yield strength of 281 MPa, ultimate tensile strength of 363 MPa and a medium elongation of 13.3%, which was mainly attributed to the interaction of the hard second phase particles with dislocation movement and the lowest basal-type texture intensity that favored the basal slip.
In-situ synthesis of AlN+Mg2Si/Mg matrix composites and microstructural studies
Magnesium matrix composites with AlN and Mg2Si reinforcement are potential engineering materials for automobile and aerospace applications. Fine particulate AlN/Mg composites have been successfully in-situ synthesized using Mg alloy and Al shots and Si3N4 powder as raw materials. Reaction under argon atmosphere or SF6/CO2 protective gas atmosphere at 770 to 850°C for an hour was used to produce composites containing different volume fraction of AlN (+ residual Mg2Si) depending on the reaction temperature. The microstructures were characterized using X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy. Fine AlN particles embedded within magnesium matrix in addition to a larger size Mg2Si phase was observed after the in-situ reaction. The AlN particles were found to have formed from the prior Si3N4 agglomerates while the morphology of the Mg2Si phase was dependent upon the composition, temperature and cooling rate. Thermodynamic calculations including the equilibrium and Scheil solidification paths of the resultant alloy after the in situ reaction were performed and compared. At the same time, reaction mechanism was studied using SEM and TEM and a “core-shell” reaction mechanism was supported.
Material characterisation and mechanical properties of Al2O3-Al metal matrix composites
Journal of materials science, 2001
The mechanical properties of metal matrix composites (MMCs) are critical to their potential application as structural materials. A systematic examination of the effect of particulate volume fraction on the mechanical properties of an Al 2 O 3 -Al MMC has been undertaken. The material used was a powder metallurgy processed AA 6061 matrix alloy reinforced with MICRAL-20 TM , a polycrystalline microsphere reinforcement consisting of a mixture of alumina and mullite. The volume fraction of the reinforcement was varied systematically from 5 to 30% in 5% intervals. The powder metallurgy composites were extruded then heat treated to the T6 condition. Extruded liquid metallurgy processed AA 6061 was used to establish the properties of the unreinforced material. C 2001 Kluwer Academic Publishers
IJERT-A Study of Microstructure and Mechanical Property of Aluminium - Alumina Metal Matrix
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/a-study-of-microstructure-and-mechanical-property-of-aluminium-alumina-metal-matrix https://www.ijert.org/research/a-study-of-microstructure-and-mechanical-property-of-aluminium-alumina-metal-matrix-IJERTV2IS90017.pdf Aluminium alloys are widely used in aerospace and automobile industries due to their low density and good mechanical properties, better corrosion resistance and wear, low thermal coefficient of expansion as compared to conventional metals and alloys. The excellent mechanical properties of these materials and relatively low production cost make them a very attractive candidate for a variety of applications both from scientific and technological viewpoints. The aim involved in designing metal matrix composite materials is to combine the desirable attributes of metals and Ceramics. Present work is focused on the study of behaviour of Aluminium Cast Alloy (LM6) with and Al2O3 composite produced by the stir casting technique. Different % age of reinforcement is used. Tensile test, Impact test and wear test performed on the samples obtained by the stir casting process. optical microscope was performed to know the presence of the phases of reinforced material.
Squeeze Casting of Aluminium Metal Matrix Composites-An Overview
Procedia Engineering, 2014
Squeeze casting is the combination of the casting and forging processes that can be done with help of high pressure when it is applied during melt solidification. Applying pressure on the solidification of molten metal could change melting point of alloys which enhances the solidification rate. Moreover it refines the micro and macrostructure; it is helpful to minimize the gas and shrinkage porosities of the castings. This paper stresses the importance of squeeze casting of the Aluminium Metal Matrix Composites in all aspects: squeeze pressure, casting (melt)/ preform preheat/ die temperature, solidification rate, reinforcement particle sizes, porosity and mechanical properties.