Study On Mechanical Properties Of Titanium Alloy Structure With Spherical Inclusion

Active Structural material has been regarded as a novel multi-functional material with the capability of energy liberation via chemical reactions.At current stage,most of the active structure materials are suffered from several technical limitations such as low strength,severely fragile under explosive load and impact conditions,etc.Therefore,the pursuit of high-density,high strength,high activity structure/composite materials have become one of the most difficult and attractive issues in the material field.Herein,this thesis studied the mechanical properties of spherical inclusions titanium alloy structural materials through experimental research and numerical simulation combination method,which is meaningful for better adhibition of large scale spherical inclusions titanium alloy structural materials.Firstly,the debonding failure mechanism of the interface was obtained based on the fracture surface morphology and metallographic analysis of the specimen and a numerical simulation scheme was established via the debonding failure mechanism.Secondly,the influences on the strength of composites such as inclusions size,interfacial bonding strength and inclusion volume ratio were discussed via establishing interfacial relations between inclusions and matrixes based on cohesion model elements.Finally,the relationship between the failure strength and the matrix / inclusions geometric physical properties of such large scale spherical inclusions with titanium-based composites was obtained,which provides the technical basis for the design of this type of structure / composite utilized in the dynamic loading environment with high strain rate.The whole thesis achievements and main conclusions include:The technology of powder metallurgy for forging large size tungsten bead intercalated titanium alloy matrix / composite was discussed.Afterwards,the static tensile test of such kind of spherical inclusions with titanium alloy structure prepared by China Academy of Engineering Physics was carried out and the basic mechanical properties of the structural material were obtained.The results turned out that tensile strength of structural materials test value is between the interfacial bond strength and body strength.The distribution of stress and strain field in plane finite field inclusion was studied via using complex variable function method based on elastic mechanics and stress concentration theories.The complex variables functions of characterization displacement and stress were established via utilizing the finite field connectivity model of the matrix part of the inclusion structure.And then,the finite volume structure was introduced a correction factor to obtain an approximate solution to the inclusion of a finite field.Finally,explicit stress concentration factor expressions related to material parameters and inclusion size were obtained,which paves a new way for the design of spherical inclusions titanium alloy structural material.Fracture morphology and metallographic analysis of the specimen showed that tungsten and titanium both existed and accounted for a considerable proportion in the inclusion-free area on the failure interface.It can be considered that the interfacial layer is composed of a mixture of a titanium alloy powder and a tungsten alloy powder,and the strength of the interfacial region is lower than that of the base and the inclusion strength.The fracture mode at the fracture interface shows obvious shear fracture characteristics and the interface of the fracture principle gradually shows dimple characteristics of obvious ductile fracture,indicating that the failure mode is compound fracture,which can be used to provide evidence for determining the numerical simulation scheme of tensile failure of the test specimen.Based on the verification and confirmation of the numerical simulation model,the influences of interface strength and toughness,inclusion distribution on the mechanical properties of spherical inclusions were investigated.Increasing the interface strength is beneficial for improving the overall tensile strength of the structural material,but the effect is nonlinear and the effect shows a single additive property as the interfacial strength locates within the 50-90% range of the substrate strength.