Ti-Al3Ti metal-intermetallic laminate (MIL) composite with a cubic titanium trialuminide stabilized with silver: Selection of fabrication regimes, structure, and properties

Ti-Al3Ti metal-intermetallic laminate (MIL) composites are known as promising structural materials due to the unique combination of their specific properties. However, their application is still limited due to the extremely high brittleness of the Al3Ti phase. In this study, we attempt to address this issue by changing the D022 crystal structure of Al3Ti to the more ductile L12 structure by alloying it with silver. To select the best fabrication regimes of Ti-Ti(Al1−xAgx)3 composites, in situ synchrotron X-ray diffraction analysis was performed to reveal the chemical reactions occurring upon heating the Ti-Al-Ag sample. The analysis showed that the highest amount of Ti(Al1−xAgx)3 phase with the L12 structure appears at 930 °C. This temperature was chosen for subsequent spark plasma sintering experiments. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction analysis revealed that the sintered sample consisted mainly of Ti, Ti(Al1−xAgx)3, and a minor fraction of the Ag-Al compound distributed in the central parts of the intermetallic layers and at the grain boundaries. Modification of the titanium trialuminide crystal structure positively affected the properties of the composite, providing a 60% increase in fracture toughness. The Ag-Al phase also contributed to toughening, causing an additional crack deflection effect. •Ag stabilizes L12 crystal structure of Al3Ti in Ti-Al3Ti multilayer composite.•The maximum fraction of L12 phase in the composite is reached at 930 °C.•Modification of the Al3Ti provides 60% increase of the composite fracture toughness.•Minor Al-Ag phase causes the additional crack deflection effect.