Study On Mechanical Properties And Corrosion Resistance Of Ti-Al-Zr-Sn-M Titanium Alloy Hot-rolled And Heat-treated Sheets

Today,the world is faced with three major problems of resources,population and environment.The development and utilization of marine resourc es has become the key strategic goal of various country.Realizing the innovative development of the marine economy is inseparable from advanced high-performance marine engineering equipment.Titanium alloy is widel y used in the engineering equipment of marine environment because of its outstanding advantages such as high specific strength and good corrosion resistance.In this paper,Ti-5.5Al-3.0Zr-1.5Sn-0.3Mo-0.5Nb,Ti-5.5Al-2.0Zr-1.5Sn-0.5Mo-1.5Nb and Ti-6.0Al-3.0Zr-0.5Sn-1.0Mo-1.5Nb-1.0V high-strength corrosion-resistant titanium alloys are taken as research objects.The ingot obtained by the three VAR meltings is forged and rolled into a sheet.This paper mainl y studies the microstructur e,mechanical properties and corrosion resistance of three kinds of titanium alloy hot rolled sheets,and then obtains titanium alloy sheets with optimal comprehensive properties.Subsequentl y,the effects of annealing and solution aging processes on the m icrostructure,texture,mechanical properties and corrosion properties of titanium alloy sheets were studied in order to obtain better heat treatment process specifications for guiding the production of high-strength corrosion-resistant titanium alloy shee ts.The main research contents and results of this article are as follows:(1)Study the microstructure,mechanical properties and corrosion resistance of hot-rolled sheets of titanium alloy with different compositions.The ingot structures of the three titanium alloys are all t ypical Weiss microstructures.After slab forging and rolling,the flake?-phase bundles are fractured,bent,and recombined.Ti603titanium alloy sheet is mainly equiaxed?+?structure,which has the highest strength plastic produc t and the best comprehensive mechanical properties.Ti552titanium alloy has the lowest corrosion current densit y,the lowest static corrosion rate,and the best corrosion resistance,while Ti553 titanium alloy has the worst.(2)Study the effect of anneal ing process on the microstructure and properties of Ti603 titanium alloy sheet.After annealing,the overall structure of the hot-rolled sheet is uniforml y distributed.As the annealing temperature increases,the strip-shaped?phase decreases,the?-transition structure grows and increases,and the equiaxed?phase increases.When annealed at 740°C,the strip-shaped?phase basically disappeared,and the?-transformed structure grew,increased,and stuck together,which is a typical equiaxed structure mor phology.With the increase of the annealing temperature,the strength and Rockwell hardness of the plate show a downward trend,the plasticit y increases,the corrosion current densit y decreases,the corrosion rate decreases,and the corrosion resistance be comes better and better.After annealing at 740°C for 1 hour,the plate obtained the best mechanical properties and corrosion resistance.(3)To study the effect of solution aging process on the structure and properties of Ti603 titanium alloy sheet.When the solution temperature was increased from900°C to 930°C,the equiaxed?-phase and?-transformed structure increased significantly,and both were equiaxed.When the solution temperature increased to960°C,the equiaxed?phase and?-transformed tissue decreased,and a large number of needle-like secondary?phases appeared,and its structure changed from an equiaxed structure to a bimorphic structure.As the solution temperature increases,the strength and Rockwell hardness of the plate increase,and the plasticit y graduall y decreases,while the corrosion current density and corrosion rate show a trend of decreasing first and then increasing.The Ti603 titanium alloy sheet is subjected to solid solution at 900°C for 30 minutes and aging at 580°C for 3 hours.The comprehensive mechanical properties are the best,and its corrosion resistance is better.(4)After annealing Ti603 titanium alloy sheet at 740°C for 1 hour,the proportion of small-angle grain boundaries is 66.3%,and the proportion of large-angle grain boundaries is 33.7%.Compared with the hot-rolled sheet,the small-angle grain boundaries of the annealed sheet increased significantl y,and the large-angle grain boundaries decreased significantl y.In addition,the annealed sheet has texture in the three pole figures{0001},{112~—0},and{101~—0},but its strength is weaker than that of the hot rolled sheet.After soli d solution at 900°C for 30minutes and aging at 580°C for 3 hours,the proportion of small-angle grain boundaries increased and the proportion of large-angle grain boundaries decreased.The solid solution ageing plate has a strong basal texture in the{0001}pole figure.The texture of the solution aging sheet is slightl y stronger than that of the hot-rolled sheet,and the grain orientation in the RD direction increases significantl y at<0001>.