Ductile-Phase Toughening in TiBw/Ti-Ti3Al Metallic-Intermetallic Laminate Composites

Abstract

The concept of ductile-phase toughening was explored in a metallic-intermetallic laminate (MIL) composite comprising alternating layers of Ti 3 Al and TiB w /Ti. The laminates, in which the TiB w /Ti layers were intended to impart toughness to the brittle Ti 3 Al, were fabricated in situ by hot pressing and reaction annealing. Compared with monolithic Ti 3 Al, the MIL composite exhibited marked increases in both fracture toughness and tensile elongation because of stress redistribution and strain delocalization by in situ interfaces. The intermetallic compound a 2 -Ti 3 Al has potential as a lightweight material for high-temperature structural applications, exhibiting both high strength, and resistance to oxidation and creep. However, poor ductility and toughness at room temperature prohibit the potential applications in most fields. [1,2] Various approaches have been employed in attempts to improve the toughness of intermetallic compounds, including introducing particles, fibers, or layers of ductile inclusions. [3][4][5][6][7] However, for a given volume fraction, ductile phase inclusions in the laminate form provide the maximum toughening efficiency, followed by fiber and particulate inclusions. [4,6] Metallic-intermetallic laminate (MIL) composites can be fabricated by deposition or bonding the components. Deposition techniques, involving atomic scale transport of the component materials, are relatively costly and slow, and thus are not practical for production of large-scale components. [8,9] In contrast, reaction bonding of metallic foils afford multiple advantages, in particular the generation of well-bonded interfaces between the metal and the intermetallic components. [10,11] Furthermore, the laminated structure of the composite allows for variations in layer thickness and volume fractions of the components simply through the selection of initial foil thickness. [4,11,12] In the present work, we explore the concept of ductilephase toughening of Ti 3 Al by fabrication of MIL composites. In particular, we prepare MIL composites comprising alternating layers of TiB w /Ti and Ti 3 Al by reaction annealing TiB w /Ti foils and Al foils. Compared with pure Ti, TiB w /Ti has a greater yield strength with little sacrifice of ductility, an important attribute to satisfy the service requirements of high-temperature materials. [13] We also assess both the synthesis process and deformation behavior of the resulting TiB w /TiTi 3 Al MIL composites.The MIL composites were fabricated by an in situ method, in which alternating Al foils (100 lm thick) and 5 vol pct TiB w /Ti composite foils (500 lm thick) were stacked, followed by hot pressing at 788 K (515°C) under 75 MPa for 1.5 hours and reaction annealing under controlled temperature and pressure (Figure 1). Typical processing parameters for reaction annealing consisted of (i) an initial annealing at 943 K (670°C) for 3 hours to consume all of Al, and (ii) a densification treatment at 1473 K (1200°C) for 5 hours under 40 MPa to produce a fully dense TiB w /Ti-Ti 3 Al...

Microstructure and Fracture Behavior of Special Multilayered Steel

“…In the interface between the ML1 and Ni layer, no cracks can be found, while amounts of slip bands contribute final dimple fracture modes. During interpreting the superior strength-ductility mechanism of laminated or gradient composites, several deformation mechanisms were proposed, including the delayed necking [18], orderly plastic deformation [19], enhanced strain-hardening capacity [20,21], ideal confinement by laminated or gradient microstructure [22], etc. The similarity of these mechanisms is that they can be linked by "strain non-localization"; in other words, the heterogeneity of the microstructure effectively suppresses the degree of strain localization.…”

3D Visualized Characterization of Fracture Behavior of Structural Metals Using Synchrotron Radiation Computed Microtomography

“…We designed a brittle/ductile multilayered composite composed of brittle α 2 -Ti 3 Al constituents rendering high strength and soft α-Ti phase imparting the ductility [31]. Such a composite was prepared by diffusion reaction of alternatively stacked Ti foils and Al foils (Figure 4), and the detailed synthesis process was described in our previous work [32,33]. Compositional linear profile analysis shows the diffusion-induced composition gradient, progressively changes from the α-Ti side across the interface to the oppositeα 2 -Ti 3 Al side, which may effectively stabilize the plastic straining and provide extraordinary mechanical responses [34][35][36].…”

Superior mechanical properties and deformation mechanisms of heterogeneous laminates under dynamic shear loading

“…While these two properties are mutually exclusive in general, i.e., high yield strength usually results in limited ductility. In the last two decades, several heterogeneous microstructures have been proposed to produce both high yield strength and large tensile ductility in metals and alloys, such as bimodal/multimodal structures [1,9], gradient structures [10][11][12][13], lamella structures [8,14,15], and bimetallic laminates [16][17][18][19][20][21][22][23][24][25][26]. These heterogeneous microstructures generally have various domains with different mechanical properties, and the plastic deformation incompatibility can occur among these domains [8,[27][28][29].…”

“…Thus, stress/strain partitioning and back stress hardening have been reported to play important roles in the plastic deformation of these heterogeneous microstructures [8,17,[27][28][29]. Among these heterogeneous microstructures, bimetallic laminates have great advantages for structural applications due to the fact that superior tensile properties can be achieved by regulating microstructural parameters, such as microstructures across the interface, hardness difference between plates, and interface spacing [16][17][18][19][20][21][22][23][24][25][26].…”

“…The mechanical properties and the deformation mechanisms in bimetallic laminates have been widely studied and well understood under quasi-static conditions [16][17][18][19][20][21][22][23][24][25][26], while their plastic deformation behaviors under high strain rates are still unclear until now. As we know, the flow and facture behavior of materials under impact loading should be dramatically different from that under quasi-static conditions since thermal softening induced by adiabatic heating, strain rate effect and inertia effect can significantly affect the plastic deformation and fracture mechanisms [30][31][32][33][34][35] [36][37][38][39][40][41][42][43].…”