| Zircaloy are widely used as a major nuclear fuel cladding material in current pressurized-water nuclear reactors because of their good corrosion resistance and outstanding mechanical properties.However,the transformation of crystal structure of Zr exists at 850? to 950?,which from ?-phase?smaller neutron absorption cross section?to ?-phase?against for the service of zircaloy as cladding materials?.Another serious problem of Zircaloy is the bad reaction with water at 900? above.Thus,the traditional commercial Zr alloys cannot satisfied requirements since the development of Accident Tolerant Fuels?ATF?has become the goal of nuclear power reactors.Ti3AlC2 is a kind of layered carbides of MAX phase that have been demonstrated to feature an special combination of characteristic of ceramic and metal.With satisfactory resistance to neutron irradiation,it has been the potential candidates of advanced nuclear materials as the refractory coating that the ATF concept.However,it was scarcely studied on bonding behavior or inter-facial diffusion of MAX phase and Zr alloy.In this paper,the interface diffusion between Zircaloy and Ti3AlC2 was studied in a electric current aided under two different heating modes.It was found that the effective diffusion temperature of Al atoms of Ti3AlC2 into zirconium alloy to form Al-Zr alloy phases was dramatically reduced with electric field.The activation energy we calculated for such electric-current-aided diffusion was only 6.9k J/mol that is much lower than previously reported 38 k J/mol of Zr-Ti2 Al C couple.Also,the effect of the electronic wind effect and joule heat cannot be neglected.When a Ti C coating was deposited on Ti3AlC2 surface by PVD to control the interface reaction,the diffusion of Al can be controlled effectively without the decreasing of shear-force values.The bonding of Zr-Ti3AlC2 is great influenced by the grain orientation and stoichiometric ratio of Ti C interlayer.Ti C?111?grain orientation and non-stoichiometric ratio with Ti vacancy are advantageous to the joining.SEM / EDS,Raman analysis were used to research the bonding and fracture mechanism of samples after shear test finished.The obtained results show that Zr-Ti3AlC2 joint fracture at the interface of Ti3AlC2 and Zr/Al alloy layer and with Ti C interlayer,the fracture exists in Zr and Ti C layer interface.Since Zr C was found in side of the Zrwhich can infer zirconium atoms can be dissolved into the Ti C layer.It can be the bonding mechanism of joint when the Ti C layer exists. |
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