Fabrication And Properties Of NiTi Fiber Reinforced Ti-Al Metal-Intermetallic Laminate Composite

The structures of fiber-reinforced Ti-Al metal-intermetallic laminate composites have a number of performance characteristics such as anisotropy,and geometric and physical nonlinearities.Thus,there are many important and complex performance issues in the research,manufacture and application.In this paper,the anisotropic properties of NiTi fiber reinforced Ti-Al metal-intermetallic laminate composites?SMAFR MIL composites?were studied.We focused on studying of the preparation process and reaction mechanism both unidirectional NiTi fiber reinforced Ti-Al intermetallic laminate composite?unidirectional SMAFR MIL composite?and orthogonal NiTi fiber reinforced Ti-Al metal-intermetallic laminate composite?orthogonal SMAFR MIL composite?.The layout mode of NiTi fiber effect on the mechanical properties and damping properties for SMAFR MIL composite was mainly investigated,and the mechanism of NiTi fiber in SMAFR MIL composites were revealed.The results are given as follows:?1?No matter the initial unit structure was"Ti-NiTi-Al-Ti"or"Ti-Al-NiTi-Al-Ti"laminate,the NiTi fibers were uniformly distributed in the middle of the intermetallic layer after hot press sintering.In the intermetallic compound layer,a special"block"region composing of NiTi fibers,Al₃Ti single-phase region and two-phase mixed region was formed.The calculation result of free energy of Al3Ni phase and Al3Ti phase using HSC 6.0 software showed that Al3Ni phase taked precedence over Al₃Ti phase and two phases alternately formed a unique lamellar structure.In addition,Single phase region was formed around the two-phase mixed region.?2?The density and elastic modulus of SMAFR MIL composites with different phase volume fractions were measured.The results showed that the density of SMAFR MIL composites was 3.8⁴.1 g/cm³ and the elastic modulus was 140¹65 GPa.The perpendicular to the layer microhardness test of SMAFR MIL composite showed that the microhardness was regularly distributed.?3?Tensile test,compressive test and three-point bending test were conducted on MIL composite,unidirectional SMAFR MIL composite and orthogonal SMAFR MIL composite,and therir fracture morphologies were observated and analyzed.These results showd that the interface plaied an important role during tensile process when these SMAFR MIL composites are under tensile stress condition,and the ultimate tensile strength of unidirectional SMAFR MIL composite was higher than that of orthogonal SMAFR MIL composite due to the perpendicular to the direction of tensile stress interface between NiTi fiber and intermetallic decreased the tensile properties of orthogonal SMAFR MIL composite.Then,the orthogonal SMAFR MIL composite have better compressive strength than the unidirectional SMAFR MIL composites under compressive stress due to the crack arrest of orthogonal fibers.Under flexural stress,the plastic deformation and fracture of NiTi fiber contribute importantly to the fracture toughness of SMAFR MIL composite through the calculation of fracture energy.However,the debonding behavior of fibers caused in some layers of orthogonal SMAFR MIL composite resulted in its lower toughness than that of unidirectional SMAFR MIL composite.?4?The analysis result of the damping properties about unidirectional and orthogonal SMAFR MIL composites indicated that NiTi fibers lost their some damping properties after hot press sintering.The NiTi fibers still displaied good damping properties owe to their pseudo-elastic properties.So the inherent damping of NiTi fibers and interface damping dominated in the SMAFR MIL composite.It can be concluded that the orthogonal SMAFR MIL composite showed a higher damping performance because of the more interface and NiTi fiber numbers in orthogonal SMAFR MIL composite than in unidirectional SMAFR MIL composite.