TiAl alloy is an ideal high-temperature lightweight structural material with a temperature above 600 ° C, but the low room temperature plasticity limits the wide application of TiAl alloy. In order to improve the above-mentioned shortcomings of TiAl alloys, researchers tried to introduce Ti2AlN, a ternary layered MAX phase with both metal and ceramic properties, into TiAl alloys, and strive to improve the plastic toughness of TiAl alloys while ensuring their strength. Although Ti2AlN / TiAl composites have important application prospects, their comprehensive mechanical properties are still some distance away from people's expectations. This is mainly because there is still a lack of understanding of the nature of the microscopic deformation behavior of the composites, which makes it impossible to establish effective composite The design criteria of the microstructure of the material have not fully tapped the potential of Ti2AlN to enhance plasticization.
Recently, Professor Sun Dongli of Harbin Institute of Technology and Han Xiuli and co-directed Dr. Liu Pei (corresponding author) and others published the title "The role of incoherent interface in evadingstrength-ductility trade-off dilemma of Ti2AlN / TiAl" composite: Acombined in-situ TEM and atomistic simulations "article. This paper reports that a Ti2AlN (103) / TiAl (111) non-coherent interface with moderate bonding strength and unique atomic structure can simultaneously play the dual roles of "interface softening" and "interface strengthening" during compression deformation, which helps To simultaneously improve the compressive strength and plastic deformation ability of Ti2AlN / TiAl composites.
Article link: https://doi.org/10.1016/j.compositesb.2020.107794
The research team first used in-situ transmission electron microscopy to discover the unique phenomenon that the Ti2AlN (103) / TiAl (111) non-coherent interface can simultaneously nucleate and annihilate dislocations during compression deformation, and then use first-principles and molecular dynamics simulations It is clarified that the dislocation nucleation / annihilation dominated by the non-coherent interface mainly comes from the multiplicity and non-uniformity of the interface bonding. Based on this unique interface-dislocation mechanism, the compressive failure strain and compressive strength of the non-coherent interface configuration of Ti2AlN (103) / TiAl (111) are higher than those of the coherent interface configuration of Ti2AlN (0001) / TiAl (111) Increased by 90.48% and 13.01% respectively, so this non-coherent interface helps to improve the compressive strength and plastic deformation ability of the composite at the same time. This research not only provides theoretical guidance for the optimal design of Ti2AlN / TiAl composite interface, but also has important practical significance for promoting the basic research and engineering application of high-performance metal matrix composites.
Based on the non-uniformity and multiplicity of Ti2AlN (103) / TiAl (111) non-coherent interface bonding, when the non-coherent interface configuration is subjected to a compressive load, the weakest area of interface bonding is Ti2AlN (103 ) The non-coherent region of the Al2 atomic sequence on the surface can nucleate the initial dislocations to open the plastic deformation, and then the weaker interface bonding region can evolve into a local disordered region to annihilate the formation of secondary dislocations, and the stronger interface bonding region Maintain the overall stability of the interface. Therefore, Ti2AlN (103) / TiAl (111) helps to increase the compressive strength and plastic deformation ability of Ti2AlN / TiAl composites at the same time.