Comparative study of Al-TiAl composites with different intermetallic volume fractions and particle sizes (original) (raw)
Related papers
Journal of Alloys and Compounds, 2018
A novel method to fabricate aluminum metal-matrix composites reinforced by mono-dispersed TiAl 3 intermetallic particles, by cold-roll bonding, heat treatment, followed by accumulative roll bonding (ARB), is demonstrated. Roll bonding of 1100-Al sheets inserted with Ti powder was carried out at room temperature with 50% thickness reduction. Complete conversion of the initial Ti particles into TiAl 3 intermetallic was achieved by a post-rolling annealing treatment at 590 C for 2 h, which results in the formation of coarse TiAl 3 particles along the interface of the original 1100-Al sheets. Subsequent ARB process was applied to break up and disperse the TiAl 3 phase, and after 5 cycles of ARB, an aluminummatrix composite with mono-dispersed TiAl 3 particles of submicron sizes was achieved. The Al matrix also undergoes dynamic recrystallization during the ARB process to result in a fine-grained microstructure (size less than 500 nm). The hardness, tensile strength and elongation of the Al/TiAl 3 composite were found to increase with the number of ARB cycles. The tensile strength of the Al/TiAl 3 composite after the 5th cycle reaches 400 MPa, which is significantly higher than the 300 MPa of monolithic 1100-Al processed in the same way. The tensile elongation of the Al/TiAl 3 composite after 5 cycles of ARB exhibits a good value of~8%, with a ductile fracture mode. This is the first successful attempt to achieve Al-matrix nanocomposites reinforced by mono-dispersed TiAl 3 intermetallic based on an ARB method.
2008
The aim of this work is to report the effect of the high energy milling processes, on fabrication of aluminium matrix composite powders, reinforced with a homogeneous dispersion of the intermetallic Ti 3 Al reinforcing particles. Design/methodology/approach: MA process are considered as a method for producing composite metal powders with a controlled fine microstructure. It occurs by the repeated fracturing and re-welding of powders particles mixture in a highly energetic ball mill. Findings: Mechanical alloying, applied for composite powder fabrication, improves the distribution of the Ti 3 Al intermetallic reinforcing particles throughout the aluminium matrix, simultaneously reducing their size. Observed microstructural changes influence on the mechanical properties of powder particles. Research limitations/implications: Contributes to the knowledge on composite powders production via MA. Practical implications: Gives the answer to evolution of the powder production stages, during mechanical alloying and theirs final properties. Originality/value: Broadening of the production routes for homogeneous particles reinforced aluminium matrix composites.
Selected properties of the aluminium alloy base composites reinforced with intermetallic particles
2006
Purpose: The main aim of this work is to investigate two types of intermetallics TiAl and Ti 3 Al as reinforcement and their influence on selected properties and microstructure of aluminium matrix composites. Design/methodology/approach: Aluminium matrix composites were produced employing the atomised aluminium alloy AA6061 as metal matrix, when as reinforcement TiAl and Ti 3 Al intermetallics particles were used. The powders were cold pressed and then hot extruded. To evaluate the effect of mechanical milling two types of ball mills were used: a low energy (horizontal ball mill) and a high energy one (eccentric ball mill). Reinforcement contents for both processes 5, 10, 15 % by weight. To determine hardness Vickers tests were performed. Microstructure observations were made by optical microscopy and scanning electron microscopy SEM. Findings: Based on the examinations carried out one can state that the mechanical milling can produce composites powders with homogenous distribution of reinforcement particles. The mechanically milled and extruded composites show finer and better distribution of reinforcement particles what leads to better mechanical properties of obtained products. Research limitations/implications: In order to evaluate with more detail the possibility of applying these composite materials at practical application, further investigations should be concentrated on the interface reaction of the matrix and reinforcing particles during elevated temperature exposition and their influence on mechanical properties. Practical implications: The composites materials produced by this way have shown significant improvement of the mechanical properties in comparision with matrix materials. Good properties of the composites make them suitable for various technical and industrial applications. Originality/value: It should be stressed that the materials as intermetallic compounds with outstanding mechanical properties and good thermal stability were developed making them a powerful material to be used in this kind of composites as the alternative for the reinforcements usually investigated and utilized to the composites materials production-alumina or silicon carbide.
Ultrafine-grained Al composites reinforced with in-situ Al3Ti filaments
Materials Science and Engineering: A, 2016
Ultrafine-grained (UFG) Al matrix composites reinforced with 15 and 30 vol% in-situ Al 3 Ti filaments were fabricated by extrusion of Al-Ti powder mixtures followed by solid-state reactive diffusion. Fine Al powder particles (1.3 mm) heavily deformed the coarser Ti particles (24.5 mm) into filaments during extrusion. Upon a subsequent operation of hot isostatic pressing (HIP), the micrometric Al 3 Ti filaments elongated along the extrusion direction and formed in situ in the UFG Al matrix. Fabricated composites are free of pores and voids with perfect bonding created at the Al-Al 3 Ti interfaces. In parallel, a small portion (2.4 vol%) of nanoscale γ-Al 2 O 3 particles, which originate from native amorphous films on fine Al powders, formed in situ and were homogenously dispersed in the Al matrix. The microstructures of asextruded and after HIP composites were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD). Owing to the presence of nanometric γ-Al 2 O 3 particles with Al high angle grain boundaries (HAGBs), the UFG Al matrix remained stable even after HIP at 600°C for 9 h. The mechanical properties and creep performance of composites at testing temperatures of up to 600°C were systematically studied. The Al-Al 3 Ti composites exhibited a combination of increased strength and Young's modulus in addition to excellent creep performance and structural stability, which indicates that the studied composites are potential structural materials capable of service at elevated temperatures.
Alumina–Ti aluminide interpenetrating composites: microstructure and mechanical properties
Materials Letters, 2003
The microstructure and mechanical properties of dense interpenetrating phase Al 2 O 3-TiAl-Ti 3 Al composites fabricated by pressure-assisted thermal explosion of TiO 2-Al powder blend have been studied. The unusual wavy morphology of aluminide-Al 2 O 3 interface matching the lamellar ga 2 aluminide structure was formed due to big difference between oxygen solubility in g and a 2. Crack deflection by alumina grains and crack bridging by the more ductile intermetallic may control the fracture toughness of these composites.
Materials Science Forum, 2005
This work analyses the production of Al based composites with particulate reinforcement, via mechanical alloying. Composites were produced by mixing Al and NbAl 3 powders by high energy mechanical alloying, under liquid nitrogen atmosphere, followed by cold pressing and hot sintering; and by controlling NbAl 3 phase precipitation in liquid Al (in situ formation of the reinforcement). Results on composite produced from powders showed better distribution and incorporation, besides finer dispersion of particles in the matrix when mechanical alloying is employed. In this case, high dispersion on particulate phase was found despite predominance of small particles; there are no evidence of interface formation. When composites are produced by in situ formation of NbAl 3 intermetallics, results showed that the formation of the reinforcement directly from the liquid matrix and the peritectic reaction between NbAl 3 and liquid Al, provide a perfect reinforcement/matrix interface. Products showed good mechanical properties, good wear behavior and reduced thermal expansion.
Materials Today: Proceedings, 2018
In the present study, Al/Al 3 Tinanocomposites were prepared by stir casting technique. The reinforcing intermetallic Al 3 Ti phases were generated by in-situ reaction between nanosized TiO 2 particles and molten Al. Microstructural investigations revealed the presence of plate, needle and nanosized Al 3 Ti and Al 2 O 3 particles. Morphological evolution of the Al 3 Ti phase with respect to its content and its effect on the grain size, texture, dislocation density and their type were analysed. At higher vol%, Al 3 Ti phases acquire plate shaped morphological features which changes to needle shaped at lower vol% of Al 3 Ti. The overall dislocation density and screw dislocation density in the nanocomposites has been found to increase with increase in vol% of the intermetallic phase. Texture analysis revealed that Brass {011} <211> and P {011} <111> are the dominant texture components in the nanocomposites, which indicate particle stimulated nucleation and recrystallizationof grains.
2002
The 2XXX series aluminium alloys reinforced with intermetallics present a special behaviour due to the reaction between matrix and reinforcement. This reaction forms an interphase that in¯uences the mechanical and chemical behaviour of the composite, reducing the capability of the material to improve its properties after heat treatment. In this work, an approach is made to the study of this interphase, using particulate intermetallics with the same chemical and stoichiometric composition but obtained in different ways: mechanical alloying and gas atomising. A microstructural study was carried out by SEM, including qualitative analysis, showing the chemical gradient formed at the interphase both as-extruded and after T6 treatment. The mechanical behaviour of the interphase is studied through nanoindentation that allows the determination of hardness and Young modulus. Finally, all these properties are correlated with a fractrographic study of the fracture mechanisms. A harder interphase is formed for the mechanically alloyed system promoting a transgranular cleavage fracture micromechanisms, while intergranular cleavage fracture is found in atomised intermetallic containing composites.
Al–FeAl–TiAl–Al2O3 composite with hybrid reinforcement
Journal of Materials Processing Technology, 2005
The process of obtaining cast aluminium composite of dispersive structure and hybrid reinforcement has been presented in the article. An Aluminium alloy (AlMg 2 ) was modified with a powder mixture which, when in reaction with aluminium, reinforced the matrix with intermetallic phases and aluminium oxide. According to the technological conception, an assumption was made, that the cast composites would be produced in technological procedure shown in . The reinforcing phases were using Fe-Ti-Al powder mixtures with aluminium oxide formed in a self-propagating high-temperature synthesis (SHS). The structure and phase composition of the composite powder used for the matrix alloy modification are shown in .