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...