Study On The Hot Deformation Behavior Of Pure Molybdenum Slab

Molybdenum is widely used becaused of excellent performance.In general, molybdenum alloy play a role in all industries.In recent years,with the application progress of pure molybdenum in molybdenum targets,increasingly stringent requirements of molybdenum target,require a higher purity and a certain grain size,high density,good surface quality.Because this material is commonly used in high temperature conditions,also quire molybdenum materials have high temperature mechanical properties.Molybdenum target is prepared by powder metallurgy with thermoplastic processing,hot processing affects the final properties of molybdenum products,so the hot process on microstructures and properties of molybdenum products have important significance.This paper adopt Gleeble-1500 thermal simulation machine for compressing experiment on pure molybdenum slab prepared by powder metallurgy under the condition of deformation temperature is 1060~1300℃,deformation rate is 0.01~10s-1,deformation amount is 80%. Drawed the true stress-strain curve and analysised the relation between the stress, deformation temperature and deformation rate. Characterized the microstructure of material by used Olympus optical microscope and JSM-5600 scaning electron microscope.Studied on the changes of tissue before and after deformation,dynamic recrystallization and the average grain size grew law,established the average grain size of the model and the dynamic recrystallizaion volume fraction model.Analysised and calculated the deformation activation energy of pure molybdenum slab by used Arrhenius model combined with the true stress-strain curve,and constructed constitutive equation.Used THV-50 MDX Senior Vickers hardness tester test the hardness of molybdenum after hot deformation,studied the relationship between the hardness,temperature,and deformation rate,established the hot processing map of pure molybdenum slab,formed a hot processing guidelines. The results of the study show that:The pure molybdenum slab flow stress-strain curves had significant peak when deformation rate is 0.01s-1, the curves is wavy when deformation rate is 10s-1.The flow stress was related to the deformation temperature and strain rate,the flow stress decreased with increasing deformation temperature,increased with increasing deformation rate.Calculated the constitutive equation of the pure molybdenum plate is: [( )] [ ]/(RT)10343.3exp0.0092sinh106.4477.113ε&′-′= s.Dynamic recrystallization average grain size is greater when the deformation temperature is higher and strain rate is smaller, the average grain size is finer and more internal cracks when the deformation temperature is lower and deformation rate is greater.The best hot processing temperature is 1250~1300℃,the deformation rate is 0.01~0.22s-1.