| Titanium-based composites are widely used in the aerospace industry due to high specific strength,specific stiffness and low density,so their service temperature is generally high.As one of the failure modes of materials under high temperature environment,creep failure influences the stabilization and persistency factors of material.So studying the high-temperature creep and endurance properties of materials is of great significance for the service of materials at high temperatures.In this paper,Sintered?TiBw+?Ti,Zr?5Si3?/TA15 composite was prepared by powder metallurgy combined with in-situ autogenous technology,and the hot rolling process was obtained to obtain a rolled composite material to systematically study high temperature creep and endurance properties of TA15 composites.And TA15 alloy was purchased for performance comparison.And we tested the high temperature creep and endurance properties.Then we also analyzed the change of composite properties before and after rolling,the high temperature creep failure process and creep deformation mechanism of the rolled composites.The creep properties of the rolled composite material after different heat treatments were tested and the effects of heat treatment on the creep properties of the rolled materials were analyzed.The matrix structure of the sintered composite material is a nearly equiaxed or short rod structure.The TiBw is distributed in a network in the matrix,and the Si element is precipitated in the?/?phase interface or the?phase by the?Ti,Zr?5Si3 particles.The structure is transformed into a lamellar structure after rolling,at the same time,the whisker reinforcement undergoes a certain degree of fracture and steering during the rolling process,which improves the degree of connectivity of the matrix,and the number of silicide increases and the distribution is more uniform.The tensile test results show that the rolling process improves the strength and plasticity of the composite because of grain refinement,work hardening and the improvement of matrix connectivity.Heat elastic modulus test shows that the rolling process improves the heat elastic modulus of the material to some extent by changing the distribution of reinforcements in the matrix.The thermal expansion coefficient test indicates that the rolling process has little effect on the thermal expansion coefficient of the material.It is found that the strength and heat elastic modulus of rolled material are higher than those of TA15 alloy.The high temperature creep tests show that the rolling process of improves the creep life of the material by 15.85%under 650?,225MPa by changing the matrix structure and the distribution of TiBw and silicide.Compared with the TA15 alloy,the creep rupture life of the rolled composite material was increased by 30-60 times,and the material deformation is significantly reduced;The stress index n of the rolled composites at 600°C,650°C,and 700°C is calculated by steady-state creep constitutive equations,which are 5.21,5.34,and 6.07,respectively.The creep process of composite is controlled by dislocation climbing.Respectively,the creep activation energy marked Q is 351.05kJ·mol-1.The creep resistance of the rolled composite is better than that of TA15 alloy.A creep rupture life prediction equation for rolled composites in 650?was established.Comparing the endurance properties of the two materials,it is found that the tensile stress of the rolled composite is 3.2 times that of the TA15 alloy when the rupture life is 50h at650?.Microscopic analysis shows that the interface between TiBw and matrix is the main source of crack propagation.The precipitation distribution of silicide effectively hinders the dislocation motion and significantly improves the properties of the material.The microscopic analysis shows that the microstructure of the rolled composites is transformed into a similar sintered structure after two-phase solid solution and aging treatment,and the primary?phase in matrix is gradually decomposed.At the same time,the silicide is re-dissolved during the solid solution treatment,and is re-precipitated in the aging process,and the silicide size increases with the aging temperature increases.While the size of the acicular?+?phase increases."Overaged"occurs when aging time increases to 8h.The high temperature creep test shows that the materials'endurance properties decrease with the increase of solution temperature and the increase of solid solution time.Since the aging process is beneficial to the precipitation of silicide and the reduction of the number of grain boundaries,increasing the aging temperature can improve the endurance properties of the material.However,"over-aging"occurs when the aging time is increased to 8 hours,resulting in a decrease in the endurance properties. |
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