Research On Microstructure And Fatigue Behavior Of New Zrtialv Alloys

In recent years,China has made great progress in the fields of aerospace and high-speed trains,and put forward higher requirements for materials.ZrTiAlV alloy has a good development space in the field of aerospace because of its excellent properties of titanium alloy and zirconium alloy.Engineering materials will inevitably be affected by the alternating load in the actual use process,which will lead to fatigue failure.Therefore,it is of great significance to study the fatigue behavior and fatigue fracture mechanism of materials.In this paper,a new ZrTiAlV alloy developed by our researchgroup was used as the research object.The forged ZrTiAlV alloy and the annealed ZrTiAlV alloy were respectively studied with MTS fatigue testing machine at room temperature.According to the phase transition temperature measured by DSC,the annealing process was developed.With the universal material testing machine to test the mechanical properties of annealed state ZrTiAlV alloys,the test results show that in 700 ? annealing,heat preservation 2h alloy has the best comprehensive mechanical properties.The high cycle fatigue s-n curves of ZrTiAlV alloy in forging state and annealed state were analyzed.The fatigue limit of wrought zirconium alloy was 720 MPa and the fatigue strength ratio was 0.65,and that of annealed zirconium alloy was 790 MPa and 0.71.At the stress level of 825 MPa,the fatigue life of zirconium alloys in the two states is equal.When the stress level is greater than 825 MPa,the fatigue stress of the wrought zirconium alloy is higher than that of the annealed zirconium alloy.With the increase of cycle times,the annealed zirconium alloys show better fatigue resistance.The basic characteristics of fatigue fracture were analyzed by sem.It was found that the impurities and defects in the alloy,as well as the surface state of the sample,had great influence on the fatigue performance of the alloy.By comparing the mechanical properties of wrought zirconium alloys with that of annealed zirconium alloys,it is found that forged zirconium alloys have a great influence on fatigue strength due to their poor matching of strength and plasticity.However,the comprehensive mechanical properties of zirconium alloys are remarkably improved after annealing.Therefore,cyclic hardening occurs during fatigue testing,which is beneficial to improve fatigue strength.Through TEM observation and analysis of the area near the fracture,it can be seen that there is a large amount of dislocation accumulation near the/interface,which should be the main reason for the stress concentration and the formation of fatigue crack source.