Evolution Of Microstructures And Mechanical Properties Of Pure Tantalum Foils During Annealing

Since the thickness of the metal foil is equivalent to its grain size,the mechanical behavior during plastic processing or micro-forming is often affected by the size effect.In this paper,pure tantalum foil is used as the research object.The microstructure and mechanical properties of tantalum foil annealed at different temperatures are analyzed by optical microscope,scanning electron microscope,EBSD,transmission electron microscope and uniaxial tensile experiment.The influence law of the microstructure and mechanical properties of tantalum foil,and the micro-mechanism of annealing strengthening phenomenon in the recovery stage of tantalum foil is discussed.The main conclusions obtained are as follows:(1)Annealing temperature has a significant effect on the microstructure and texture of tantalum foil.The rolled tantalum foil grains are fibrous,mainly forming an alpha texture with {001}<110> as the component;when the annealing temperature is lower than 900?,the tantalum foil is still dominated by fibrous structure,but in { 111}//Sub-crystals are formed in the ND orientation area,and as the annealing temperature increases,the subcrystals grow,and ? texture is gradually formed in the tantalum foil;when the annealing temperature is 900?,recrystallization occurs in the tantalum foil Crystal nucleus,{001}//ND-oriented area also generates {111}//ND-oriented recrystallized nucleus,the{001}<110> texture in the ? texture component gradually decreases,and ? texture is formed at the same time;When the annealing temperature reaches 1000?,the tantalum foil has been completely recrystallized,mainly {111}//ND-oriented recrystallized grains.At this time,the texture of the material is completely transformed into a ? texture;as the annealing temperature continues to increase,The grains of tantalum foil gradually grow up,and the ? texture component is stronger,and {111}<110> texture is the strongest.(2)Through the room temperature tensile test of tantalum foils with different annealing temperatures along the RD and TD directions,when the tantalum foil is stretched along the RD direction,the tensile strength of the tantalum foil is the highest when annealed at800?,the highest is 639 MPa,and the yield strength is The highest,the highest is 605 MPa,and the elongation is the highest when annealing at 1000?,reaching 29.9%;when the tantalum foil is stretched in the TD direction,the tensile strength of the tantalum foil is the highest when the tantalum foil is annealed at 800?,the highest is 621 MPa,and the yield strength is the highest,reaching 605 MPa.The elongation is the highest when annealed at 1000?,reaching 30.5%.The tantalum foils stretched along the two RD and TD directions both exhibit annealing strengthening during low temperature annealing,and softening after annealing after recrystallization.(3)Through the EBSD characterization of the samples after the tantalum foil is stretched and deformed at different annealing temperatures,after the tantalum foil is deformed,There are microstrips in the {111}//ND-oriented area,and uneven orientation occurs in the grains of the same orientation.(5)The abnormal annealing strengthening phenomenon occurs after lowtemperature annealing.On the one hand,the microcracks in the tantalum foil are easily generated near the shear band,and on the other hand,the influence of impurity elements in the tantalum foil;the tantalum foil grows up in grains.The strengthening phenomenon of the stage is caused by the size effect,and the microscopic mechanism is caused by the larger proportion of the oxide film on the surface of the tantalum foil.