Study On The Effect Of Aging Treatment On Microstructure And Mechanical Property Of ZrTiAlV Alloy

Zr and Zr alloys are of great importance in aerospace. Military, nuclear and chemicalindustries because of low thermal neutron absorption and density, small expansioncoefficient, adequate strength and ductility, excellent anti-irradiation and corrosionresistance. Now, the tensile strength of main Zr-based alloys, such as Zr-2, Zr-4, Zr-2.5Nband so on, can not meet the strength requirement of structural material in plenty domains.In this dissertation, the objects of research were47Zr-45Ti-5Al-3V alloy, with an aim ofinvestigating the microstructure evolution and mechanical properties of them. Simul-taneously, the kinetics of β→α precipitation was studied.The results showed that the alloy was composed of single β phase after solutiontreatment at850/1050oC, and occurred the transformation of β→α phase during agingprocess. The shape of α phase was acicular. At the same aging temperature, the amount ofα phase gradually increased with increasing the aging time. With increasing the agingtemperature, the amount of α phase decreased and the size of α phase increased in thethickness and the length. The amount of α phase at the equilibrium state decreased too.The effect of aging temperature on the mechanical properties of47Zr-45Ti-5Al-3Valloy was investigated after solution treatment at850and1050oC. At the same agingtemperature, the hardness value of alloy firstly increased to a peak value, and thendecreased with increasing aging time for the samples solution-treated at850and1050oC.The hardness peak decreased with increasing aging temperature.The weight percentages of α phase were determined by the method given above, andthe kinetics of α phase precipitation was investigated. The results showed that, therelationship between the weight percentage of α phase and annealing time follows theAvrami equation. The solution temperature has a little effect on the time exponent (n), butthe rate constant of α phase (k) decreased with the solution temperature decreasing. Thevalue of n increased, whereas the value of k decreased with increasing the agingtemperature. The relationship between t0.5(the time that the weight percentages of α phaseachieved one half) and the aging temperature follows Arrhenius equation, the apparentactivation energy of α phase precipitation increased with decreasing the solutiontemperature.