Study On Microstructures,Mechanical Properties And Cold Forming Of TC16 Titanium Alloy Bars

TC16 titanium alloys are considered to be ideal materials for the production of titanium alloy fasteners in the aviation industry due to their excellent strength and toughness,fatigue resistance and corrosion resistance,etc.At the same time,the TC16 titanium alloy bars have excellent cold working plasticity in the annealed state,and their room temperature forging ratio reaches 1:4.They can be used directly after compression or after solution and aging.Therefore,it is of great significance to study the microstructure,properties and cold deformation behavior of TC16 titanium alloy bars.In this paper,TC16 titanium alloy hot-rolled bars were taken as the object to study their room temperature compression forming properties,and the multi-pass cold-rolled tests of TC16 titanium alloy sheets were produced.At the same time,the effect of heat treatment on the microstructure and mechanical properties of TC16 titanium alloy bars and plates were studied.The main research contents and conclusions are as follows:The effect of heat treatment process on the microstructure and mechanical properties of TC16 titanium alloy hot-rolled bars were studied.The results showed that the structures of alloy after annealing were composed of equiaxed α phase,intergranular β phase and a small amount of lamellar α phase.The tensile strength was 878 MPa,the elongation was 15%,and the reduction of area was 64%.After solution at 760～840°C and aging at 550°C,the alloy structures were composed of equiaxed α phase,intergranular β phase and needle-like secondary α phase precipitated in β phase.The strength and microhardness of the alloy were improved to varying degrees,resulting in Aging strengthening,the alloy had excellent comprehensive mechanical properties after solution at 800℃ and aging at 550°C.At the same time,the tensile fracture characteristics of the TC16 titanium alloy bars under different heat treatment conditions were analyzed.The macroscopic fracture modes were ductile fractures,and the microscopic fracture mechanisms were dimple-type fractures.Room temperature compression experiment results showed that the reduction rate of the annealed TC16 titanium alloy can reach 80%,and it had excellent cold forming ability.While the reduction rates of solution and aged alloys were 51.8% and 31.2%,respectively,the cold forming ability was poor,and the failure mechanism was shear fracture.At the same time,the annealed TC16 titanium alloy cold heading bolt experiment was carried out,and the head reduction rate of the bolt could reach 80%,and 45° micro-cracks appeared on the side surface of the bolt head.Based on the results of compression experiments,the multi-pass cold-rolled tests of annealed TC16 titanium alloy sheets were produced.The results showed that the annealed alloy had excellent cold rolling formability.When the deformation was greater than 73%,the α grains were elongated along the rolling direction to form fibrous structure.The tensile strength and microhardness of the alloy were increased by 25.2% and 14.6%,respectively,and obvious deformation strengthening was obtained.The effect of annealing treatment on the microstructure and mechanical properties of TC16 cold-rolled plates was studied.When the cold-rolled deformation was greater than 47%,complete recrystallization occurred,forming equiaxedα-grain structures,and the mechanical properties were lower than the annealed alloy bars to varying degrees.The experimental datas of cold rolling of TC16 titanium alloy will provide technical support for process developmentthe of cold rolling of slab and cold drawing of wire in the future.