Intermetallic and Quasicrystalline Aluminum Alloys
Mechanically Alloyd Aluminium Alloys Based on Intermetallic and Quasicrystalline Phases
Tech Area / Field
- MAT-ALL/High Performance Metals and Alloys/Materials
8 Project completed
Senior Project Manager
Mitina L M
MISIS (Steel and Alloys), Russia, Moscow
- NIKIMT (Institute of Assembly Technology), Russia, Moscow
- Institut für Festkörper und Werkstofforschung, Germany, Dresden\nUniversity of Oxford / Department of Engineering Science, UK, Oxford\nFrenzelit-Werke GmbH & Co. KG, Germany, Bad Berneck
Project summaryThe project is aimed at obtaining new of aluminum composite materials on the basis of intermetallic and quasicrystalline phases, which will be synthesized by the method of mechanical alloying (?A) from powder metals. The compositions and structure of powders will be the subject of detailed investigation. The powders obtained by the MA technique will be mixed in precise proportions and compacted into bulk samples by the use of explosive pressing technique. The formation of ultra dispersed structure at rather low homologous temperature of synthesis will allow the production of aluminum materials with improved physico-mechanical properties.
The purpose of the project is to combine two techniques characterized by the extremely low processing temperatures – mechanical alloying and explosive pressing - for the production of new high-strength aluminum-based alloys with nano-crystalline structure.
The systems Al-Ti, Al-Ni, Al-Cu-Fe will be used as research objects of the present project. Pure aluminium and aluminium-based intermetallic phases will be taken as the binding matrix. Special attention will be given to obtaining alloys on the basis of quasicrystalline phases.
The majority of aluminium alloys known today and used to structural applications have the maximum yield strength of about 600 MPa. It is a widespread belief that the capabilities of hardening an aluminium matrix by dispersing precipitates of the second phase in age-hardened alloys are practically exhausted. On the other hand, the exceptional hardness and thermodynamic stability of intermetallic phases of aluminium with nickel, titanium, etc. suggest a possibility of a further considerable increase of aluminium alloys’ strength. However, alloys consisting of intermetallic compounds alone are friable, brittle, and hence poorly suited to structural applications. Therefore, for the purposes of enhancing the mechanical characteristics of aluminium alloys in the last few years, in place of conventional metallurgical melting, increasingly often powder technologies of rather low temperatures synthesis are used to obtain these alloys. Communications appear in scientific literature about the possibilities of achieving the yield strength of 1200 and even 1550 MPa in aluminium-based alloys (dispersion-hardened amorphous alloys). Below the temperature of synthesis, particularly dispersed alloy structure can be obtained, with correspondingly higher possible levels of mechanical properties.
The purpose of the project is to combine two techniques of low temperature treatment – mechanical alloying and explosive pressing - for producing new high-strength aluminium-based alloys with nanocrystalline structure.
Al-Ti, Al-Ni, Al-Cu-Fe systems will be the project’s research objects. The intermetallic compounds in the indicated systems are characterized by strong interaction of components, have high yield strength and melting point. In the Al-Ti system there are three prospective intermetallic compounds: Al3Ti, AlTi and Ti3Al. High yield strength and corrosion resistance are characteristic for all these compounds. Similar intermetallic compounds with high melting point form in the system Al-Ni. In the system Al-Cu-Fe the formation of both intermetallic and quasicrystalline phases is possible. The particularities of electronic structure of quasicrystals predetermine a number of properties which are unusual and attractive for applications: high hardness, strength and wear resistance; high corrosion resistance, low friction coefficient. Aluminium-based quasicrystalline samples obtained in preliminary experiments have hardness magnitudes characteristic of steels (5 GPa and higher). Even if a binding matrix of pure aluminum is used, the hard intermetallic impurities of the indicated systems will allow considerable values of bulk material strength to be attained. But even more promising is the use of aluminium-based solid solutions as a binding matrix, as well as intermetallic phases with wide compositional range of homogeneity.
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