Ultra-strong and ductile multifunctional titanium alloy and methods for preparing the same

Abstract

The present invention relates to an ultra-strong and ductile multifunctional titanium alloy made from two or more metal elements. The titanium alloy has a molecular formula of Ti a Zr b Hf c Nb d Sn e , a, b, c, d, and e represent atomic percentages of the metal elements, falling within the ranges of 45≤a≤55, 36≤b≤43, 3≤c≤6, 3.5≤d≤7.5, and 1.5≤e≤3. The titanium alloy exhibits an initial microstructure characterized by an equiaxed ultra-fine grain (UFG) structure, which is reinforced by hierarchical nanostructures formed during subsequent deformation. By synergistically amalgamating the benefits of superior mechanical performance, pseudoelasticity, and biocompatibility, the alloy is anticipated to emerge as a promising contender for advanced damping devices or shock absorbers within the aerospace and automotive sectors. Additionally, it can be employed as biocompatible implants, including stent grafts or guide wires, in medical applications.

What is claimed is: 
     
         1 . An ultra-strong and ductile multifunctional titanium alloy made from two or more metal elements, wherein the titanium alloy has a molecular formula of Ti a Zr b Hf c Nb d Sn e , wherein a, b, c, d, and e represent atomic percentages of the metal elements, falling within the ranges of 45≤a≤55, 36≤b≤43, 3≤c≤6, 3.5≤d≤7.5, and 1.5≤e≤3, the titanium alloy exhibits an initial microstructure characterized by an equiaxed ultra-fine grain (UFG) structure, wherein the UFG structure is reinforced by hierarchical nanostructures formed during subsequent deformation. 
     
     
         2 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the titanium alloy comprises 48 at. % of Ti, 39 at. % of Zr, 4.5 at. % of Hf, 6.3 at. % of Nb, and 2.2 at. % of Sn. 
     
     
         3 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the hierarchical nanostructures comprise nanotwins, and wherein one or more nanobands are confined within the nanotwins. 
     
     
         4 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the UFG structure has an average size of 300 nm to 2 μm. 
     
     
         5 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the titanium alloy demonstrates a tensile strength of approximately 1.75 GPa, coupled with a uniform elongation of at least 20%. 
     
     
         6 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the titanium alloy endures over 1000 fatigue cycles under a constant tensile stress of 1.4 GPa. 
     
     
         7 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the titanium alloy exhibits an almost-complete recovery from deformation ranging between 4% and 5%. 
     
     
         8 . The ultra-strong and ductile multifunctional titanium alloy of  claim 1 , wherein the titanium alloy achieves a maximum recoverable strain of approximately 7%. 
     
     
         9 . A method for preparing an ultra-strong and ductile multifunctional titanium alloy sheet, comprising the following steps:
 weighing at least two raw materials with a purity higher than 95%,   wherein the at least two raw materials comprise Ti, Zr, Hf, Nb, and Sn;   melting the at least two raw materials through arc melting under a pure argon atmosphere to obtain a molten alloy;   drop casting the molten alloy into a water-cooled copper mold;   cold rolling the as-cast alloy to achieve a thickness reduction ranging from 97% to 99% to obtain a cold-rolled alloy sheet;   wrapping the cold-rolled alloy sheet in an iron sheet and annealed between 800° C. to 900° C. for an annealing time under a continuous flow of argon atmosphere, followed by air cooling to obtain the titanium alloy sheet.   
     
     
         10 . The method of  claim 9 , wherein the titanium alloy containing the at least two raw materials has a molecular formula of Ti a Zr b Hf c Nb d Sn e , and wherein a, b, c, d, and e represent atomic percentages of the metal elements, falling within the ranges of 45≤a≤55, 36≤b≤43, 3≤c≤6, 3.5≤d≤7.5, and 1.5≤e≤3. 
     
     
         11 . The method of  claim 9 , wherein the step of melting the at least two raw materials through arc melting under a pure argon atmosphere to obtain a molten alloy comprises a series of melting and remelting processes, amounting to a total of 7-8 cycles. 
     
     
         12 . The method of  claim 9 , wherein the annealing time is between 20 seconds to 20 minutes. 
     
     
         13 . The method of  claim 12 , when the annealing time is in a range of 25 to 45 seconds, the titanium alloy demonstrates a tensile strength of approximately 1.75 GPa, coupled with a uniform elongation of at least 20%. 
     
     
         14 . The method of  claim 12 , when the annealing time is in a range of 45 to 75 seconds, the titanium alloy demonstrates a tensile strength of approximately 1.5 GPa, coupled with a uniform elongation of at least 15%. 
     
     
         15 . The method of  claim 12 , when the annealing time is in a range of 12 to 20 minutes, the titanium alloy demonstrates a tensile strength of approximately 1.2 GPa, coupled with a uniform elongation of at least 17%.