High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

Abstract

The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

Phase formation of nanolaminated Mo2AuC and Mo2(Au1−xGax)2C by a substitutional reaction within Au-capped Mo2GaC and Mo2Ga2C thin films

“…30,31 It has also been shown that Si from Al-alloy can diffuse into Ti 2 AlC crystals during infiltration process, forming either Ti 2 (Al,Si)C solid solution or Ti 2 AlC + Ti 2 SiC two phase regions. 32 Another example is that Ti 3 SiC 2 can decompose when in contact with powder or molten Al at a temperature above 600 °C, due to out-diffusing Si dissolved in the Al matrix. 6,7 The mechanisms for this out-diffusion in vacuum or in oxidizing ambient has been reported on Ti 3 SiC 2 and Ti 2 AlC systems, where the substoichiometric MAX phases eventually collapsed and decomposed into binary carbide, intermetallic phases, and oxides, as applicable.…”

Effects of Tantalum on Microstructure Evolution and Mechanical Properties of High-Nb TiAl Alloys Reinforced by Ti 2 AlC

“…The density and thermal expansion coefficient of Ti 2 AlC particles are 4.11 g/cm 3 and 8.8 × 10 −6 K −1 and are close to those of TiAl, whose corresponding values are 3.84 g/cm 3 and 12 × 10 −6 K −1 [26], which improves the preparation of the Ti 2 AlC-reinforced TiAl-based alloys by avoiding the phenomena of segregation of the ceramic particles and reducing the inner stress between the ceramic and the matrix. The ceramic phase of Ti 2 AlC usually combines properties of both metals and ceramics [27], which possess both ductility and stiffness. However, the distribution of carbides must be uniform and the length-diameter ratio of carbides needs to improve.…”

Cutting resistance of metal-ceramic interpenetrating composites

“…MMCs, IPCs can exhibit significant advantages such as multifunctionality and macroscopically isotropic properties [4] and, very recently, it has been shown that they can also have excellent mechanical properties [5]. It is also possible to incorporate relatively high volume fractions of one phase in the other.…”