Feasibility of aluminium nitride formation in aluminum alloys (original) (raw)
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Metallurgical and Materials Transactions A, 2016
In-situ fabrication of the reinforcing particles directly in the metal matrix is an answer to many of the challenges encountered in manufacturing metal matrix nanocomposite materials. In this method, the nanosized particles are formed directly within the melt by means of a chemical reaction between a specially designed metallic alloy and a reactive gas. The thermodynamic and kinetic characteristics of this chemical reaction dictate the particle size and distribution in the matrix alloy, as well as the nature of the particle/matrix interface, and consequently, they govern many of the material's mechanical and physical properties. This article focuses on aluminum-aluminum-nitride nanocomposite materials that are synthesized by injecting a nitrogen-bearing gas into a molten aluminum alloy. The thermodynamic and kinetic aspects of the process are modeled, and the detrimental role of oxygen is elucidated.
Materials
Aluminium nitride (AlN) is an important technical ceramic with outstanding strength and thermal conductivity that has important applications for advanced heat sink materials and as a reinforcement for metal-based composites. In this study, we report a novel, straightforward and low-cost method to prepare AlN powder using a vacuum tube furnace for the direct nitridation of loose aluminium powder at low temperatures (down to 500 ∘C) under flowing high-purity nitrogen. Small amounts of magnesium powder (1 wt.%), combined with aluminium, promote nitridation. Here, we characterise the effects of time (up to 12 h) and temperature (490 to 560 ∘C) on nitridation with the aim to establish an effective regimen for the controlled synthesis of an aluminium nitride reinforcement powder for the production of metal matrix composites. The extent of nitridation and the morphology of the reaction products were assessed using scanning electron microscopy and X-ray diffraction analyses. AlN was detecte...
Modified directed melt nitridation of pure aluminum block using magnesium as an external dopant
Journal of Materials Science, 2007
Modified directed melt nitridation of pure Al block was investigated by using magnesium as an external dopant at 1373-1573 K during the flowing high pure N 2 . The products were characterized using optical microscope, X-ray diffractometer, scanning electron microscope and electron probe microanalysis techniques. Experimental results show that it is a lower costs way to synthesize AlN matrix or Al matrix materials by modified directed melt nitridation through adapting proper processing parameters. The weight gain rate increased significantly with the treating temperature and Mg content. Apparent activation energy of 208.7 KJ/mole was obtained in terms of the reaction rate involving nitridation, evaporation and transportation. AlN reinforced Al matrix material was fabricated with less Mg and AlN particles were enriched in the top part of the product with distinct boundary to the bottom Al. however, when the content of Mg was up to 10 wt% and treated at higher treating temperature, AlN phase dominated in the product with a relative looser structure.
Synthesis of Aluminum-Aluminum Nitride Nanocomposites by Gas-Liquid Reactions
2013
An innovative method has been developed for synthesizing aluminum-aluminum nitride nanocomposite materials wherein the reinforcing nano-sized aluminum nitride particles are formed in-situ in a molten aluminum alloy. This method, which circumvents most issues associated with the traditional ways of making nanocomposites, involves reacting a nitrogen-bearing gas with a specially designed molten aluminum alloy. The method ensures excellent dispersion of the nanoparticles in the matrix alloy, which is reflected in enhanced mechanical properties. In this thesis, the author reviews the limitations of the conventional methods of manufacturing nanocomposites and develops thermodynamic and kinetic models that allow optimizing the in-situ gas-liquid process to produce quality nanocomposite material. Also, in this thesis, the author reports the measured room temperature and elevated temperature tensile properties of materials that were made by the optimized process and compares the measured values to their counterparts obtained for the base alloy. A 75 pct. increase in room temperature yield strength is obtained when the base alloy is reinforced with one pct. nano-size aluminum nitride particles and this significant increase in yield strength is accompanied by only negligible loss of ductility.
The production of AlN-rich matrix composites by the reactive infiltration of Al alloys in nitrogen
Acta Materialia, 2002
Aluminium nitride (AlN)-Al matrices reinforced with Al 2 O 3 particulate have been fabricated by reactive infiltration of Al-2% Mg alloy into Al 2 O 3 preforms in N 2 in the temperature range of 900-1075°C. The growth of composites of useful thickness was facilitated by the presence of a Mg-rich external getter, in the absence of which composite growth is self-limiting and terminates prematurely. Successful growth of composites has been attributed to the reduction in residual oxygen partial pressure brought about by the reaction with oxygen of highly volatile Mg in the getter alloy. The microstructure of the matrix consists of AlN-rich regions contiguous with the particulate with metal-rich channels in-between, thereby suggesting that nitridation initiates by preferential wicking of alloy along the particle surfaces. The increase in nitride content of the matrix with temperature is consistent with hardness values that vary between~3 and 10 GPa.
A Review on the Possibility for Nitriding of Aluminium Alloys
Annual Journal of Technical University of Varna, 2021
The present paper provides a brief overview of the possibilities for nitriding the surface of Al-alloys. This treatment is still attracting scientific attention, not only as a means to increase the industrial life of materials but also as a way to comply with the current ecological requirements. On the whole, the purpose of such a process is to improve the mechanical properties like surface hardness and wear resistance of the Al-alloys, especially in automotive industry where "lightening" the whole construction is of great importance for reducing the fuel consumption. The paper, further, sets out to examine the influence of the technological parameters of this thermochemical treatment on the thickness of the formed nitride layer and on the mechanical properties on one hand and the naturally formed oxide on the surface of the Al-alloys on the other hand. Drawn, in the end, are some conclusions about the potential benefits of nitriding and expressed is the specific need for its thorough research in the future.
In situ reacted titanium nitride-reinforced aluminum alloy composite
Journal of Materials Processing Technology, 2002
In this paper, an aluminum matrix containing titanium nitride particles was fabricated by an in situ process in which nitrogen gas reacts with titanium in the liquid melt to form TiN. The tensile and yield strength increased by up to 20% after the formation of TiN particles in the Al alloy matrix, whilst the hardness increased by up to 27%. The abrasive and sliding-wear resistance increased with the in situ formation of the TiN particles.
In-Situ Manufacturing of Aluminum-Aluminum Nitride Castable Nanocomposite Materials
2012
In this contribution we present a novel manufacturing process in which aluminum nitride nanoparticles are synthesized in-situ within a specially formulated aluminum alloy by means of a controlled gas-liquid reaction to produce an aluminum matrix composite material wherein nano-sized aluminum nitride particles are homogeneously dispersed. Also in this contribution we address the effect of the manufacturing process parameters and the chemical composition of the matrix alloy and reactive gas on the efficiency of the aluminum nitridation reaction.
British Ceramic Transactions, 2003
in production methods, higher purity, and better knowledge of physical and chemical properties initiated intensive Aluminium nitride samples were produced by a reaction research for new applications to utilise the very special bonding process using AlN and Al powders with akeproperties of these materials. like and equiaxed morphologies as starting materials. Various methods of producing AlN powder are Changing the particle sizes and morphologies of the known.4-15 Nearly 130 years ago, the initial preparation of aluminium starting powders led to changes in degree AlN via the reaction of liquid Al with N 2 gas was reported.16 of reaction and microstructure of the resulting reaction Slack and McNelly17 used aluminium uoride and ammonia bonded aluminium nitride ceramics. At 25 wt-%Al, the gas to produce AlN. Total nitriding of Al powders was degree of reaction showed a maximum, decreasing at achieved in the work of Boitier et al.18 by the addition of higher aluminium concentrations. T he degree of CaCO 3. Another method of manufacturing AlN is carboreaction was increased by increasing nitrogen gas thermal reduction of aluminium oxide,19-21 which involves owrate or nitriding temperature. It was also found to reacting nely mixed Al 2 O 3 and carbon powders in N 2 be increased by reducing the average particle size of containing gas at temperatures in the range 1373-2073 K. the Al starting powder, the green bulk density, or the The aerosol synthesis route for producing AlN oVers an sample thickness, and also by choosing akelike morphalternative to conventional powder preparation methods.22 ology. SEM and optical micrographs of reaction bonded High purity powders can be obtained by using molecular aluminium nitride samples revealed the pore structure precursors as starting reactants. One group has described and morphology of primary and secondary aluminium aerosol reactors for AlN synthesis using AlCl 3 and NH 3 as nitride. BCT /604 gas phase reactants.23 Other workers have described solution phase methods for producing AlN, using metal organic Dr Salahi
Formation of Aluminium Nitride during Sintering of Powder Injection Moulded Aluminium
Materials Science Forum, 2009
A detailed transmission electron microscopy study of the structure of aluminium nitride formed during sintering of powder injection moulded aluminium is presented. A polycrystalline layer formed on Al particle surfaces exposed to a nitrogen atmosphere. This layer consisted of fine, rod-like crystallites of hexagonal AlN typically aligned normal to the Al surface. A double layer of AlN separated by a thin layer of Al was observed at the interfaces between Al grains. In this report, the structure of the nitride is characterised and its influence on sintering is discussed.