Study On Semi-Melting Deformation Treatment Process Of Zr-45Ti-5Al-3V Alloy Assisted By Electric Field

Zirconium and zirconium alloys are widely used in nuclear industry due to their high hardness,corrosion resistance and radiation resistance.In recent years,a series of ZrTiAlV alloys have been prepared by Yanshan University on the basis of TC4 titanium alloy.Among them,Zr-45Ti-5Al-3V alloy has high tensile strength,but its plastic deformation ability is poor and its structure and properties are not uniform,which greatly limits its wide application in the field of space vehicles.In this paper,a new semi-melting deformation treatment process of Zr-45Ti-5Al-3V alloy assisted by electric field is proposed to improve the comprehensive mechanical properties of Zr-45Ti-5Al-3V alloy.The Zr-45Ti-5Al-3V alloy was treated by electric field-assisted semi-melting deformation at 1200°C,1400°C and 1600°C by spark plasma sintering system.The variation of pressure,voltage,current,temperature and displacement with time was analyzed.The thermal,electrical and mechanical coupling simulation of Zr-45Ti-5Al-3V alloy during semi-melting deformation treatment was carried out by using MSC.Marc finite element software.The effects of different sintering parameters on temperature and stress distribution were analyzed.The variation of temperature and stress fields with sintering parameters during semi-melting deformation treatment was revealed.After semi-melting deformation at 1200°C and 1400°C,the grain of the alloy is composed of coarse β phase and needle-like or slab-like α phase which is secondary to the interior of the grain.The α phase interweaves in the grain interior and separates the matrix of β phase,showing a typical "net basket" shape.In addition to the α and β phases,hexagonal sub-oxide δ’-ZrO phases and intermetallic compound Zr5 Ti phases appear in the alloy after semi-melting deformation at 1600°C.δ’-ZrO phases are stacked by polyhedral layers approximating spheres,and are evenly distributed in the grains and grain boundaries with the morphology of free dendrites.Zr5 Ti interlaces with each other in the β phase grains with the morphology of slabs.The fracture morphology of the alloy after semi-melt deformation at 1200°C and 1400°C is typical plastic dimple at 500°C.Among them,the alloy after semi-melting deformation at 1200°C has the best plastic deformation ability.Its yield strength,tensile strength and elongation are 340.0 MPa,674.2 MPa and 23.1%,respectively.Due to the existence of brittle δ’-ZrO phase,the fracture morphology of the alloy after semi-melting deformation at 1600°C shows a typical brittle fracture mode during high temperature tensile process.The high temperature compression resistance of the alloy after semi-melting deformation treatment is obviously better than that of the original material under electric field,and with the increase of the semi-melting deformation treatment temperature,the high temperature compression resistance of the alloy increases gradually.Semi-melting deformed alloy at 1600°C has the best high temperature compressive mechanical properties,and its comprehensive mechanical properties are characterized by typical "tension-compression asymmetry".The true stress-strain curves of the alloy under the action of high temperature compression deformation at 600°C-800°C are deduced by MSC.Marc software.The effects of electric field-assisted semi-melting deformation treatment temperature and high temperature compression temperature on the compressive mechanical properties of the alloy are analyzed.The force-displacement curves obtained directly by SPS equipment in the process of electric field-assisted high temperature compression deformation treatment are established.The calculation method of real stress-strain curve.