Preparation And Properties Of Continuous Mo Wire Reinforced Ti/Al₃Ti Laminate Composites

Ti-Al intermetallic compounds have become one of the hotspots in the research of high temperature structural materials because of their unique properties.It has a wide application prospect in aerospace,warships,weapons and other fields owing to its light specific gravity,high specific strength,high elastic modulus,excellent oxidation resistance and creep resistance.However,defects such as the brittleness at room temperature,poor toughness,to a great extent,limit its development and application.In this dissertation,the Mo-Ti/Al₃ Ti laminated composites are successfully prepared using vacuum hot pressing sintering method via accede to Ti layer as the ductile layer in addition to adding the high performance continuous Mo wire.The effects of different processing parameters on the microstructure of the composites are investigated and the mechanical properties are analyzed.Besides,deformation and fracture behavior during the failure process of Mo-Ti/Al₃ Ti laminate composites are analyzed.Mo wire is acceded to the Al₃ Ti layer can improve the plasticity and strength of the Ti/Al₃ Ti composites.The hot pressing time and temperature have a great effects on the composites’ microstructure.The increase of sintering temperature and holding time could ensure the matrix microstructure uniformity and compactness,but intensify the interfacial reaction of Mo wires and metal substrate.However,the reduced sintering temperature and holding time is not enough to generate Al₃ Ti.The optimum sintering parameters of Mo-Ti/Al₃ Ti laminated composites are obtained by exploring the preparation process.Scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）are used to characterize the microstructure and elemental distribution of Mo-Ti/Al₃ Ti laminate composites.EDS analysis results show that Mo element existed only in the reaction layer of Mo wire and its matrix,does not diffuse into Al₃ Ti matrix.The interface of the composites are analyzed,and the bonding is excellent without obvious defects and voids.XRD was used to determine the phase of the composites.The results show that Mo wire and the matrix generated three cyclic reaction layers,with Mo wire as the center,from the inside and outside being respectively Al8Mo3,Al5 Mo,Al12Mo phase.XRD results show that other major compounds were identified are Ti,Mo,Al8Mo3,Al5 Mo,Al12Mo,Al₃ Ti,Al₃Ti0.8V0.2 phase and a small amount of unreacted Al phase.In this dissertation,the basic physical properties such as density,hardness and elastic modulus of Mo-Ti/Al₃ Ti laminate composites were tested.The quasi-static compression and tensile properties of the composites with different volume fraction of Ti were tested.The failure mechanism of the composites was analyzed.The results show that the addition of Mo wire makes the mechanical properties of the composites increased significantly.With Ti volume fraction increasing,the compressive strength and fracture strain of Mo-Ti/Al₃ Ti increase,the compressive strength reaches 1300 MPa and the fracture strain is 4.42%.The tensile measurement results show that the tensile strength of Mo-Ti/Al₃ Ti composites is greatly improved by the addition of Mo wire,up to 430 MPa.The bending test results prove that the bending strength of Mo-Ti/Al₃ Ti composites are much higher than Ti/Al₃ Ti,which increase 157 MPa.The Mo-Ti/Al₃ Ti maximum bending strength reached 568.3MPa.The failure analysis results show that the strain to failure of the Al₃ Ti matrix is transgranular,and the toughness of the composite material is improved significantly by the behavior of the debonding and pull-out of the Mo wire and the existence of ductile Ti layer.