KR100337426B1 - Low Cost and High Strength α+ βTitanium Alloy and its Manufacture - Google Patents

Abstract

The present invention relates to a low cost high strength α + β titanium alloy and a method of manufacturing the same, the object of which is harmless to human body and low cost β phase stabilization on α + β alloy based on titanium (Ti) -aluminum (Al) system It is to provide a low-cost high-strength α + β titanium alloy and a manufacturing method having excellent room temperature and high temperature tensile properties by adding an element.

The present invention is a titanium alloy; Low-cost, high strength α + β titanium alloy composed of iron (Fe): 3.5 to 4.5 weight ratio, silicon (Si): 0.3 to 1.0 weight ratio, aluminum (Al): 1.5 to 6.5 weight ratio, and titanium (Ti): balance. In providing.

Description

Low cost and high strength α + β titanium alloy and its manufacture

The present invention relates to a low cost, high strength α + β titanium alloy and a method for manufacturing the same, and particularly to vanadium (V), which is expensive of Ti (titanium) -6Al (aluminum) -4V (vanadium), which accounts for 60% or more of total titanium alloy usage. The present invention relates to a low cost, high strength α + β titanium alloy having a low cost element and improved mechanical properties at room temperature and high temperature.

Titanium alloys have been applied to various industries such as aviation, aerospace, marine, sports, medical, etc. due to their high specific strength, excellent corrosion resistance and biocompatibility. The major equilibrium phases in titanium alloys are α and β phases. Depending on the type and amount of alloying elements, the equilibrium phases stable at room temperature may be either α phase or β phase. As such, titanium alloys are generally classified into α alloys, β alloys, and α + β alloys at room temperature. The most widely used alloy is α + β alloy, which is based on Ti (titanium) -Al (aluminum) system which stabilizes the α phase and has a solid solution strengthening effect, and includes molybdenum (Mo) and iron (Fe). ), Β-phase stabilizing elements such as vanadium (V) and chromium (Cr), and neutral elements such as zirconium (Zr) and tin (Sn). The most representative alloy of α + β alloy is Ti (titanium) -6Al (aluminum) -4V (vanadium). Occupies.

However, since the development of titanium alloys has been mainly made for aerospace purposes, alloy elements have been selected based on physical properties rather than prices, and have been made of alloy systems that are expensive and not easy to supply. In particular, vanadium (V), which is used for Ti (titanium) -6Al (aluminum) -4V (vanadium), is an expensive element and has harmful toxicity to the human body. Therefore, there are many constraints on the special purpose of the alloy. Therefore, efforts have been made to develop low-cost new alloys by replacing vanadium (V), which is a representative β-phase stabilizing element, with other β-phase stabilizing elements which are inexpensive and relatively harmless to the human body. As a result, Ti (titanium) Alloys such as -5Al (aluminum) -2.5Fe (iron) and Ti (titanium) -6Al (aluminum) -0.1Si (silicon) have been developed, but the content of iron (Fe), which is a β-stabilizing element, has not been optimized. There are several problems, such as the tendency of the mechanical properties at room temperature and high temperature to be somewhat insufficient.

The present invention has been made in view of the above problems, and an object thereof is excellent by adding a β-phase stabilizing element, which is harmless to humans and inexpensive, to an α + β alloy based on a titanium (Ti) -aluminum (Al) system. It is to provide a low cost high strength α + β titanium alloy having a normal temperature and high temperature tensile properties and a method of manufacturing the same.

The present invention is a titanium alloy; Low cost high strength α + β titanium alloy composed of iron (Fe): 3.5 to 4.5 weight ratio, silicon (Si): 0.3 to 1.0 weight ratio, aluminum (Al): 1.5 to 6.5 weight ratio and titanium (Ti): balance In providing.

1 is the maximum tensile strength and elongation of TFS alloy at room temperature

2 is the maximum tensile strength and elongation of TFS alloy at high temperature (400 ° C.).

3 is a silicide structure of Ti (titanium) -4Fe (iron) -ySi (silicon)

(a) 0.5 wt% silicon (Si), (b) 1 wt% silicon (Si)

(c) 2 wt% silicon (Si), (d) 4 wt% silicon (Si)

4 shows the maximum tensile strength and elongation of Ti (titanium) -4Fe (iron)-(0.5,1) Si (silicon) -xAl (aluminum) alloy at room temperature (hatched area: annealed alloy Ti (titanium) -6Al ( Aluminum) -4V (vanadium) alloy maximum tensile strength, dotted line: main alloy Ti (titanium) -6Al (aluminum) -4V (vanadium) alloy maximum tensile strength)

FIG. 5 shows the maximum tensile strength and elongation of Ti (titanium) -4Fe (iron)-(0.5,1) Si (silicon) -xAl (aluminum) alloy at high temperature (400 ° C.) (hatched area: annealed alloy Ti (titanium) Maximum tensile strength of -6Al (aluminum) -4V (vanadium) alloy, dotted line: Maximum tensile strength of main alloy Ti (titanium) -6Al (aluminum) -4V (vanadium) alloy)

The present invention is based on the most representative Ti (titanium) -6Al (aluminum) -4V (vanadium) alloy of the α + β alloy based on a titanium (Ti) -aluminum (Al) system, the expensive vanadium (V) ) Is replaced with (3.5-4.5 weight ratio) low-cost iron (Fe), and (0.3-1.0 weight ratio) silicon (Si) is added to improve the room temperature and high temperature mechanical properties, and the β-phase stabilization element is changed. The present invention relates to a new low cost high strength α + β titanium alloy in which the aluminum (Al) content of the alloy is changed to (1.5 to 6.5 weight ratio) by changing the α phase stabilizing element corresponding thereto.

Table 1 shows the composition of the present invention compared with the conventional alloy, the semi-permanent made of pure copper (Cu) after manufacturing the master alloy in the argon (Ar) atmosphere using an arc melting furnace for the production of the present invention alloy It was produced by centrifugal casting method using a metal mold. In addition, in order to homogenize the structure of the alloy after casting and to remove casting defects such as pores, hot isostatic pressing was performed at 900 ° C. and 100 MPa for 2 hours. The main composition of the present invention prepared by the above method is iron (Fe); 3.5-4.5 weight ratio, aluminum (Al); 1.5 to 6.5 weight ratio, silicon (Si); 0.3 to 1.0 weight ratio, and titanium (Ti); It is the rest.

As shown in FIGS. 1 and 2, the minimum composition for stabilizing the β phase at room temperature is 3.5 wt%, and the composition of the iron at less than 3.5 wt% It is not possible to stabilize a sufficient amount of β-phase at room temperature. In addition, from the room temperature and high temperature mechanical properties of the titanium (Ti) -iron (Fe) -silicon (Si) ternary alloy, it can be seen that the composition of 4wt% is better than the 2wt%.

In addition, when 4.5 wt% or more of iron (Fe) is added, a weak ω phase and an intermetallic compound such as TiFe are formed, thereby rapidly decreasing the ductility of the alloy. Therefore, the maximum content of iron (Fe) in the present alloy system is preferably set to 4.5 wt%.

Silicon (Si) added to improve the high temperature tensile properties is 0.3 to 1.0 by weight, and when the silicon (Si) content is increased as shown in FIG. 3, it is not dissolved in the silicon (Si) titanium base, Precipitates in form. When the precipitates had a size of 1 μm or more, the mechanical properties of the alloy were lowered, and the composition of silicon (Si) in which these precipitates were formed was 1 wt% or more. Therefore, the maximum silicon (Si) content in the present invention is preferably 1wt% or less. In general, the added Si content is 0.3wt% or less. In this alloy, a maximum solid solution of 0.3wt% or more was added to simultaneously obtain a solid solution strengthening and precipitation strengthening effect of Si. That is, when more than 0.3wt% precipitates are generated by the precipitate can be improved the strength of the alloy.

As shown in FIGS. 4 and 5, the α-stabilizing element aluminum (Al) increases in strength by solid solution of aluminum (Al) to the titanium base as the aluminum (Al) content is added. However, in the present invention, when the aluminum (Al) content is added below 1.5wt%, the strength thereof is not higher than Ti (titanium) -6Al (aluminum) -4V (vanadium). The minimum amount added is preferably 1.5 wt%.

In addition, when aluminum (Al) is added 7wt% or more, it is already known that a weak Ti ₃ Al is formed and the ductility of titanium is rapidly reduced, the maximum aluminum (Al) addition amount in the present invention is 6.5wt% This is preferred.

TABLE 1

Psalm Number Alloy system (wt%) Remarks One Ti-0.5Fe-0.5Si Comparative example 2 Ti-1Fe-0.5Si Comparative example 3 Ti-2Fe-0.5Si Comparative example 4 Ti-4Fe-0.5Si Comparative example 5 Ti-0.5Fe-1Si Comparative example 6 Ti-1Fe-1Si Comparative example 7 Ti-2Fe-1Si Comparative example 8 Ti-4Fe-1Si Comparative example 9 Ti-6Al-4V Comparative example 10 ^* Ti-5Al-2.5Fe Example 11 ^** Ti-6Al-1.7Fe-0.1Si Example 12 Ti-2Al-4Fe-0.5Si Example 13 Ti-4Al-4Fe-0.5Si Example 14 Ti-6Al-4Fe-0.5Si Example 15 Ti-2Al-4Fe-1Si Example 16 Ti-4Al-4Fe-1Si Example 17 Ti-6Al-4Fe-1Si Example

Source: Materials Properties Handbook Titanium Alloys

** Source: Materials Properties Handbook Titanium Alloys, room temperature and high temperature tensile properties: α-β processed bar, high temperature tensile properties were performed at 300 ℃.

Table 2 shows the room temperature mechanical properties of the present invention compared with the conventional alloy. A bar-shaped tensile specimen with a gauge length of 22.4 mm was prepared to investigate the room temperature tensile properties. As Fe content increased, tensile strength increased, and 3.5-4.5wt% was the optimum composition. Also, when Si content is 1wt% or more, coarse silicide having a size of 1µm or more is formed to degrade mechanical properties. As the aluminum (Al) content increases, the tensile strength increases. The present invention not only has superior yield strength, tensile strength, and elongation compared to Ti (titanium) -6Al (aluminum) -4V (vanadium) alloy, but also superior mechanical properties, namely, at room temperature, to conventional low cost α + β titanium alloy. Mechanical properties of tensile strength 975 ~ 1241 MPa and elongation 6.3 ~ 16% were shown.

TABLE 2

Psalm Number Tensile Strength (MPa) Yield strength (MPa) Elongation (%) One 567 478 22.2 2 565 398 26.4 3 690 553 19.6 4 799 634 13.9 5 587 475 23.0 6 645 524 18.1 7 704 539 19.4 8 831 611 13.9 9 917 722 8.0 10 1050 920 15.5 11 1052 991 16.5 12 975 930 13.0 13 1093 1055 16.0 14 1191 1141 12.0 15 1022 871 11.0 16 1108 949 11.7 17 1241 1179 6.3

Table 3 shows the mechanical properties of the high-temperature (400 ° C) and comparative alloys of the present invention. The tensile properties of the rod-shaped specimens with a gauge length of 22.4 were prepared and investigated at high temperature of 400 ° C. The present invention not only has superior yield strength and tensile strength compared to Ti (titanium) -6Al (aluminum) -4V (vanadium) alloy, but also has excellent mechanical properties, namely high temperature (400 ° C.), compared to conventional low-cost α + β titanium alloys. ) Showed high temperature mechanical properties of tensile strength of 678 ~ 981 MPa and elongation of 8.8 ~ 18.1%.

TABLE 3

Psalm Number Tensile Strength (MPa) Yield strength (MPa) Elongation (%) One 309 218 26.3 2 327 215 23.6 3 - - - 4 532 323 12.9 5 385 256 17.8 6 403 275 17.7 7 - - - 8 585 337 11.8 9 609 450 20.5 10 720 540 - 11 798 667 17.5 12 678 442 14.8 13 779 570 17.0 14 930 731 18.1 15 750 484 11.0 16 807 598 9.9 17 981 787 8.8

The iron (Fe) is added to 3.5 ~ 4.5 wt% stabilizes the β phase at room temperature, and does not reduce the ductility of the alloy, increases the β phase fraction, increases the α / β phase boundary and solid solution. In addition, silicon (Si) added in the 0.3 ~ 1.0 wt% is strengthened by finely precipitated into titanium silicide having a solid solution in titanium or having a size of 0.1 ㎛ or less. In addition, aluminum (Al) added 1.5 to 6.5 wt% is solid solution in the matrix to stabilize the α phase to strengthen the alloy.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, the present invention provides a Ti-Al-based stabilized α phase and a solid-state stabilized element of β-stabilized element, which is rich in raw materials such as iron (Fe) and inexpensive, and does not degrade the mechanical properties of the final alloy. Content, the content of silicon (Si) added to improve high temperature mechanical properties, and the content of aluminum (Al), which is an α stabilizing element, according to the change in the amount of addition thereof, thereby optimizing the content of Ti (titanium), which is an existing α + β alloy. An alloy which is cheaper than -6Al (aluminum) -4V (vanadium) and is harmless to a living body can be obtained.

In addition, since Ti (titanium) -6Al (aluminum) -4V (vanadium) and superior low-temperature α + β alloys have been developed at room temperature and high temperature, they can be applied to various applications. .

Claims (2)

In titanium alloys; Low cost, high strength α + β titanium alloy, characterized in that it is composed of iron (Fe): 3.5 to 4.5 weight ratio, silicon (Si): 0.3 to 1.0 weight ratio, aluminum (Al): 1.5 to 6.5 weight ratio, and titanium (Ti): balance. . In a method for producing a titanium alloy; Iron (Fe): 3.5 to 4.5 weight ratio, silicon (Si): 0.3 to 1.0 weight ratio, aluminum (Al): 1.5 to 6.5 weight ratio and titanium (Ti): balance alloy consisting of argon (Ar) using an arc melting furnace Dissolve in the atmosphere to prepare a master alloy, centrifugal casting using a pure copper (Cu) semi-permanent metal mold, and the cast alloy is hot Isostatic Pressing (Hot Isostatic Pressing) for 2 hours at 900 ℃, 100 MPa conditions A low cost high strength α + β titanium alloy manufacturing method, characterized in that the homogenization and removing the casting defects such as pores.