Study On Damage In Ti₃AlC₂ Induced By Carbon And Helium Ions Irradiation

The selection of nuclear material is the main factor that restrains the research and development of advanced nuclear device.The critical structure in nuclear reactor such as fuel cladding material always work in the extreme environment with high temperature and high flux neutron irradiation.The neutron irradiation will induce large number of displacement damage and He impurity atoms due to(n,?)reaction into the materials.These processes will accelerate the swelling,embrittlement and creep of material and finally degrade its working life and affect the working state of device.As one kind of the metal ceramic,the MAX phase has the advantages of metal:easy-machining,high thermal conductivity.It also has the advantages of ceramics:excellent ductility and strength,high melting point and high corrosion tolerance.Therefore,it has been considered as the structural or functional material in advanced nuclear energy system such as Gen-IV reactor and ADS.It is of great significance to investigate the irradiation resistance of the MAX phase because this is one way to find its application value.Ti₃AlC₂samples synthesized by hot-pressing method were selected in our research.1.0 Me V C⁴⁺and 500 ke V He²⁺irradiation experiments were performed with different fluences at 300,500 and 800?C.Combining with a series of experiments,intensive research and analysis on the microstructure transformation,vacancy-type defects evo-lution,surface morphology and mechanical property change were carried out.The samples were characterized by Grazing XRD,Raman spectra and TEM to investigate the microstructure transformation induced by C and He ion irradiation.For samples irradiated at room temperature,the anisotropic variation of lattice parameters,the emergence of stacking faults and the change of micro strain were investigated.The process of phase transformation from?to?to?and finally to fcc phase was found.For samples irradiated at high temperature,they get recovered with increasing temperature.No evidences of phase decomposition and amorphization are observed in all samples.The samples were characterized by positron annihilation spectroscopy(DBS)to investigate the vacancy-type defects induced by C and He ion irradiation.For samples irradiated at room temperature,the density of vacancy-type defects increases with the increasing fluence.The type of vacancy-type defects doesn't change in samples irradi-ated with C ion but changes in samples irradiated with He ion.For samples irradiated at high temperature,the density of defects decreases with the increasing temperature.The type of vacancy-type defects also doesn't change in samples irradiated with C ion but changes in samples irradiated with He ion.These results indicate that the emergence of displacement damage and He V complex will make the density of vacancy-type defects increase.The samples were characterized by NIT and SEM to investigate the change of surface morphology and mechanical property after the C and He ion irradiation.For samples irradiated at room temperature,the value of Young modulus generally decreases with the increasing fluence in C irradiated samples.But it abnormally increases at the middle fluence.Cracks and exfoliation grow with the increasing fluence through SEM.In He irradiated samples,the value of Young modulus decreases with the increasing fluence.Additionally,some cracks and white spots on He irradiated samples were found and then blister and irregular exfoliated areas appear at higher fluence.For samples irradiated at high temperature,the value of Young modulus and surface morphology normally recover in C irradiated samples.However,in samples irradiated with He,the value of Young modulus of samples irradiated at 500?C is smaller than that irradiated at300?C.Severer blister and exfoliation exist in samples irradiated at fluence of 3.0×10¹⁷ions/cm²comparing with samples irradiated at fluence of 1.0×10¹⁷ions/cm².In C irradiated samples the irradiation effect is caused by displacement damage.In He irradiated samples the irradiation effect is caused by He bubbles.