The Effect Of Hot Deformation Behaviour,Heat Treatment On Microstructure And Mechanical Property Of ZrTiAlV Alloy

Zirconium and zirconium alloys are regarded as potential aeronautical structure materials for small thermal neutron absorption cross section,good corrosion resistance,and a long-term stability in the irradiation environment,which almost can satisfy the requirement of aeronautical structure materials for the development of space technology.In recent years,a series of ZrTiAlV alloys have been developed to meet the requirements of aerospace structural materials of high strength.In this dissertation,we mainly study the influence of the hot deformation parameters and heat treatment process on microstructure and mechanical properties in the 51.1Zr-40.2Ti-4.5Al-4.2V alloy.The hot deformation behavior of a newly developed 51.1Zr-40.2Ti-4.5Al-4.2V alloy was investigated.At low temperatures and high strain rates,the flow curves exhibited a pronounced stress drop at the very beginning of deformation,followed by a slow decrease in flow stress with increasing strain.The magnitude of the stress drop increased with decreasing deformation temperature and increasing strain rate.At high temperatures and low strain rates,the flow curves exhibited typical characteristics of dynamic recrystallization.A hyperbolic-sine Arrhenius-type equation was used to characterize the dependences of the flow stress on deformation temperature and strain rate.A microstructural mechanism map with the strain of 0.7 was presented to help visualize the microstructure of this alloy under different deformation conditions.The result showed that the 51.1Zr-40.2Ti-4.5Al-4.2V alloy was composed of single ? phase after hot deformation and occurred the transformation of ??? phase during aging process.The deformation temperature and strain rate are the main factors.At the same strain rate,the amount of ? phase gradually increased with increasing deformation temperature.With increasing strain rate,the amount of ? phase decreased at the same deformation temperature.The results showed that the alloy was composed of single ? phase with different grain size after solution treatment at 850-1050?C.The initial grain size increased with the increase of solution temperature.The aging process contributed to the ??? phase transformation.At the same aging temperature,the amount of ? phase gradually decreased and the size of ? phase decreased in the thickness and the length with increasing solution temperature.That is to say,with the decrease of initial grain size,the ? phase is easier to precipitate and the ? phase is more likely to grow up into a thicker plate strip structure.With decreasing aging temperature,the amount of ? phase increased and the thickness of lath ? phase decreased.The effect of solution temperature on the mechanical properties of 51.1Zr-40.2Ti-4.5Al-4.2V alloy was investigated after solution treatment at 850-1050?C.The hardness value of alloy decreased with the increase of solution temperature.The hardness of 51.1Zr-40.2Ti-4.5Al-4.2V alloy varied with solution temperature and aging temperature in the solution and aging treatment.At the same aging temperature,the hardness value of alloy firstly increased with increasing solution temperature.And the hardness decreased with increasing aging temperature.