Abstract
Near-net shape components composed of monolithic Ti2AlC and composites thereof, containing up to 20 vol.% Al2O3 fibers, were fabricated by powder injection molding. Fibers were homogeneously dispersed and preferentially oriented, due to flow constriction and shear-induced velocity gradients. After a two-stage debinding procedure, the injection-molded parts were sintered by pressureless sintering at 1250 °C and 1400 °C under argon, leading to relative densities of up to 70% and 92%, respectively. In order to achieve near-complete densification, field assisted sintering technology/spark plasma sintering in a graphite powder bed was used, yielding final relative densities of up to 98.6% and 97.2% for monolithic and composite parts, respectively. While the monolithic parts shrank isotropically, composite assemblies underwent anisotropic densification due to constrained sintering, on account of the ceramic fibers and their specific orientation. No significant increase, either in hardness or in toughness, upon the incorporation of Al2O3 fibers was observed. The 20 vol.% Al2O3 fiber-reinforced specimen accommodated deformation by producing neat and well-defined pyramidal indents at every load up to a 30 kgf (~294 N).
Highlights
MAX phases (M = early transition metal, A = A-group element, X = C and/or N) have emerged as promising candidates for high-temperature applications [1], combining the characteristics from both metallic and ceramic materials [2], such as good thermal and electrical conductivities, damage tolerance, low density, thermal shock [3] and oxidation resistance [4]
The Ti2 AlC powder used in this work had an irregular agglomerate shape [24]
This paper demonstrates the injection molding of monolithic and alumina fiberreinforced Ti2 AlC, followed by densification steps, as well as the characterization of mechanical properties
Summary
Among Al-containing MAX phases, Ti2 AlC stands out for its excellent longterm high-temperature oxidation resistance up to temperatures of around 1300 ◦ C [5,6] and its chemical and thermal compatibility with thermal barrier coatings, such as YSZ [7]. The report of complex shape production via existing methods and the use of additive manufacturing is still in its early stages and has been barely explored for MAX phases. This partly explains why their transfer to industrial applications is—apart from Cr2 AlC pantographs, which are used for high-speed trains in. Even though cellular and lattice architectures [8,9,10,11], as
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