Abstract
TiAl/Ti2AlNb intermetallic-intermetallic laminated(IIL)composites featuring brittle/ductile heterogeneous interfaces were fabricated through vacuum hot-pack rolling.The microstructures and the phase transfor-mation behaviors of the interfaces of the IIL composites before and after annealing at 900℃/6 h were in-vestigated.The heterogeneous interfaces are composed of four distinct regions,individually Ⅰ(βo+γ+α2),Ⅱ(βo/B2+ω)(brittle part),Ⅲ(O lath),and Ⅳ(equiaxed O)(ductile part)regions from TiAl to Ti2AlNb side.Notably,after annealing,an equiaxed O band approximately 50 μm wide was observed in region Ⅳ of the interface.In addition,a significant microhardness variation was observed between regions Ⅱ and Ⅳ of the interface,where region Ⅱ exhibited higher hardness compared to the TiAl alloy,and region Ⅳ displayed lower hardness than the Ti2AlNb alloy.The enhanced fracture toughness of the IIL composites,three times that of the TiAl base alloy,is attributed to the formation of the brittle/ductile heterogeneous interfaces and the layered design incorporating the Ti2AlNb alloy.The corresponding toughening mech-anism was further discussed.The brittle Ⅱ region plays a role in increasing crack branching,while the ductile Ⅳ region inhibits the propagation of microcracks and prevents the formation of main cracks.This work highlights the crucial role of the brittle/ductile heterogeneous interface in the toughening of lam-inated composites.Furthermore,the discovery of the O band provides novel insights into the design of TiAl/Ti2AlNb heterostructures.
NETL
NSTL
万方数据