Research On Billet Rolling Process And Mechanical Properties Of TC4 Titanium Alloy Melted In Electron Beam Cold Hearth Furnace

In the late 1980s,EB furnaces melting(Electron Beam Cold Hearth Melting)technology was introduced into the production of titanium products.This technology can significantly shorten the processing flow of titanium alloys and reduce production costs.At present,domestic research on this technology is still constrained by others,and a relatively mature rolling process has not yet been mastered.The TC4 titanium alloy ingot smelted by the EB furnace is prone to surface cracks and other macro defects in the later rolling process,which affects the mechanical properties of the material.Therefore,in-depth development of the thermal deformation behavior of EB furnace smelting TC4 titanium alloy and studying its deformation mechanism can provide theoretical guidance and experimental basis for the future production and processing of EB furnace smelting TC4 titanium alloy sheet.This article takes TC4 alloy prepared by electron beam cold hearth furnace as the research object.Gleeble 3800 thermal simulation compression testing machine is used for isothermal compression experiments.The alloy is tested at different temperatures(800?-1100?)and different strain rates(0.01 s^-1,0.1 s^-1,1 s^-1,10 s^-1),the strain amount is 50%(engineering strain),and the alloy is rolled at different temperatures(800?-1100?)and different reductions(30%,60%,90%).The research results obtained in the experiment are as follows:(1)Based the DMNR model,a dual multivariate nonlinear constitutive equation is established for the material in the dual-phase region(?+?)and single-phase(?-phase)region.The accuracy is high,the absolute error is 6.88%,4.44%,and the correlation coefficient are 0.98 and 0.99 respectively.Based on the Murty criterion and Prasad criterion,the thermal processing diagram is established for the material.The results show that the best forming area is at the temperature of 1000?-1100?,the strain rate is 0.01 s^-1?10 s^-1;(2)When the alloy is rolled at less than 1000?,the microstructure is composed of a large number of fine lamellar?phases and a small amount of?phases.The plastic deformation is dominated by basal slip and cylindrical slip.When rolled at a temperature higher than 1000?,the microstructure is composed of coarse?crystal grains and fine needle-like?phase,and the plastic deformation is dominated by cylindrical slip and pyramid slip.When the deformation is less than 90% and the temperature is 1050?,the strong plasticity is better,and the deformation is 90% and the temperature is higher than 1000?,the strength is better and the plasticity is poor.(3)When the deformation temperature is low and the deformation amount is small,the content of deformed grains is more,the proportion of small-angle grain boundaries is higher,and the plastic deformation mechanism is dynamic recovery.When the deformation temperature is high and the deformation is large,the proportion of large-angle grain boundaries is higher,and the plasticity the deformation mechanism is dynamic recrystallization.At the same time,when the single-phase region is deformed,the transition from?phase to?phase occurs,and the relationship between the?and?phases follows the Burgers orientation relationship,namely(0001)_?//(110)_?,<11(?)0>_?//<1(?)1>_?.