Superior strength-plasticity synergy in a heterogeneous lamellar Ti_(2)AlC/TiAl composite with unique interfacial microstructure

Improving the plasticity of TiAl alloys at room temperature has been a longstanding challenge for the de-velopment of next-generation aerospace engines.By adopting the nacre-like architecture design strategy,we have obtained a novel heterogeneous lamellar Ti_(2)AlC/TiAl composite with superior strength-plasticity synergy,i.e.,compressive strength of∼2065 MPa and fracture strain of∼27%.A combination of micropil-lar compression and large-scale atomistic simulation has revealed that the superior strength-plasticity synergy is attributed to the collaboration of Ti_(2)AlC reinforcement,lamellar architecture and heteroge-neous interface.More specifically,multiple deformation modes in Ti_(2)AlC,i.e.,basal-plane dislocations,atomic-scale ripples and kink bands,could be activated during the compression,thus promoting the plas-tic deformation capability of composite.Meanwhile,the lamellar architecture could not only induce sig-nificant stress redistribution and crack deflection between Ti_(2)AlC and TiAl,but also generate high-density SFs and DTs interactions in TiAl,leading to an improved strength and strain hardening ability.In addi-tion,profuse unique Ti_(2)AlC(1¯10¯3)/TiAl(111)interfaces in the composite could dramatically contribute to the strength and plasticity due to the interface-mediated dislocation nucleation and obstruction mecha-nisms.These findings offer a promising paradigm for tailoring microstructure of TiAl matrix composites with extraordinary strength and plasticity at ambient temperature.

In-situ additive manufacturing of high strength yet ductility titanium composites with gradient layered structure using N_(2)

It has always been challenging work to reconcile the contradiction between the strength and plasticity of titanium materials.Laser powder bed fusion(LPBF) is a convenient method to fabricate innovative composites including those inspired by gradient layered materials.In this work,we used LPBF to selectively prepare Ti N/Ti gradient layered structure(GLSTi)composites by using different N_(2)–Ar ratios during the LPBF process.We systematically investigated the mechanisms of in-situ synthesis Ti N,high strength and ductility of GLSTi composites using microscopic analysis,TEM characterization,and tensile testing with digital image correlation.Besides,a digital correspondence was established between the N_(2) concentration and the volume fraction of LPBF in-situ synthesized Ti N.Our results show that the GLSTi composites exhibit superior mechanical properties compared to pure titanium fabricated by LPBF under pure Ar.Specifically,the tensile strength of GLSTi was more than 1.5times higher than that of LPBF-formed pure titanium,reaching up to 1100 MPa,while maintaining a high elongation at fracture of 17%.GLSTi breaks the bottleneck of high strength but low ductility exhibited by conventional nanoceramic particle-strengthened titanium matrix composites,and the hetero-deformation induced strengthening effect formed by the Ti N/Ti layered structure explained its strength-plasticity balanced principle.The microhardness exhibits a jagged variation of the relatively low hardness of 245 HV0.2 for the pure titanium layer and a high hardness of 408 HV0.2 for the N_(2) in-situ synthesis layer.Our study provides a new concept for the structure-performance digital customization of 3D-printed Ti-based composites.

Microstructure Characteristics and Corrugation Interface Behavior of Al/Mg/Al Composite Plate Rolled Under Large Strain

Traditional rolled(TR)aluminum(Al)/magnesium(Mg)/aluminum(Al)composite plates have many bottlenecks such as multiple passes,low interlaminar strength,and weak mechanical properties.In this paper,the hard-plate rolling(HPR)method was used to prepare Al/Mg/Al composite plates under a single pass reduction of 60%.The results show that the ultimate tensile strength(UTS)of the composite plate obtained by hard-plate rolling is 262.3 MPa,and the percentage of total elongation at fracture(At)is 12.3%,which is 31.6%and 37.4%higher than that of the traditional rolling,respectively.It is attributed to the unique corrugated interlocking structure of the interface of the composite plate caused by hard-plate rolling.The shear texture produced by the Mg plate weakens the strong-basal texture.At the same time,the strong basal slip and the large amount of energy stored in the deformed grains provide favorable conditions for dynamic recrystallized(DRX)nucleation.The microstructure is deeply refined by DRX,and the strength and plasticity of the composite plate are improved synchronously.It provides scientific guidance for the development of high-performance lightweight composite plates and the research on hard-plate rolling technology and also has good industrial production and application potential.