KR20010040579A - Two phase titanium aluminide alloy - Google Patents

Abstract

A two phase titanium aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as </= 10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55 % Ti, 40 to 50 % Al, 1 to 5 % Nb, 0.3 to 2 % W, up to 1 % Mo and 0.1 to 0.3 % B. In weight %, the alloy can include 57 to 60 % Ti, 30 to 32 % Al, 4 to 9 % Nb, up to 2 % Mo, 2 to 8 % W and 0.02 to 0.08 % B.

Description

TWO PHASE TITANIUM ALUMINIDE ALLOY

Aluminized titanium alloys are disclosed in US Pat. No. 4,842,819; 4,917,858; 4,917,858; 5,232,661; 5,232,661; 5,348,702; 5,348,702; 5,350,466; 5,370,839; 5,370,839; 5,429,796; 5,503,794; 5,503,794; 5,634,992 and 5,746,846, Japanese Patent Publication No. 1988-171862; 1988-259139 and 1988-42539, European Patent Publication No. 365174 and VRRyabov et al., "Properties of the Intermetallic Compounds of the System Iron-Aluminum" Metal Metalloved, 27, No. 4, 668- 673, 1969; SMBarinov et al., "Deformation and Failure in Titanium Aluminide," published by Izvestiya Akademii Nauk SSSR Metally, No. 3, 164-168, 1984; W. Wunderlich et al., Published in "Enhanced Plasticity by Deformation Twinning of Ti-Al-Base Alloys with Cr and Si" Z. Metallkunde, 802-808, 11/1990; Published by T. Tsujimoto in "Research, Developement, and Prospects of TiAl Intermetallic Compound Alloys" Titanium and Zirconium, Vol. 33, No. 3, 19 pages, 7/1985; Provided by N.Maeda "High Temperature Plasticity of Intermetallic Compound TiAl" Material of 53 ^rd Meeting of Superplasticity, 13 pages, 1/30/1990; By N. Maeda et al., "Improvement in Ductility of Intermetallic Compound through Grain Super-refinement" Autumn Symposium of the Japan Institude of Metals, 14 pages, 1989; S. Noda et al., "Mechanical Properties of TiAl Intermetallic Compound", Autumn Symposium of the Japan Institute of Metals, 3 pages, 1988; HA Lipsitt, "Titanium Aluminides-An Overview" Mat. Res. Soc. Symp. Proc Publishing. Vol 39, 351-364, 1985; PLMartin et al., “The Effects of Alloying on the Microstructure and Properties of Ti ₃ Al and TiAl” ASM in Titanium 80, Vol 2, 1245-1254, 1980; "Effect of Rapid Solidification in Ll ₀ TiAl Compound Alloys" ASM Symposium Proceeding on Enhanced Properties in Structural Metals Via Rapid Solidification, Materials Week, 7 pages, 1986; D. Vujic et al., "Effect of Rapid Solidification and Alloying Addition on Lattice Distortion and Atomic Ordering in L1 ₀ TiAl Alloys and Their Ternary Alloys" Metallurgical Transaction A, Vol. It is the subject of many patents and publications such as 19A, 2445-2455, 10/1988 and the like.

Many such patents and publications describe how TiAl aluminide can be treated to obtain desirable properties. In addition, U.S. Patent No. 5,489,411 discloses spraying a plasma on a reelable strip, heat treating the strip to remove residual stress, placing the rough side of these two strips between the press connection rolls, and then compressing the strip. Powder metallurgy for producing aluminized titanium foils by solution annealing, cold rolling and intermediate annealing is described. U. S. Patent No. 4,917, 858 describes powder metallurgy for making titanium aluminate using titanium, aluminum and other alloying elements. U. S. Patent No. 5,634, 992 consolidates the casting and heat-treats the consolidated casting over the eutectic to form gamma grains plus alpha and gamma-phase layered colonies, and heat-treat the bottom of the eutectic to grow gamma grains in the colony structure. And a method for producing gamma aluminated titanium by heat-treating under alpha transus to reform any remaining colony structure into a structure having α ₂ rods in the gamma grains.

Still, considering the widespread efforts to improve the properties of titanium aluminate, improved alloy compositions and economical processes are needed.

The present invention relates generally to biphasic aluminated titanium alloy compositions useful for other applications such as resistive heating and structural applications.

1A-D are 200-fold optical micrographs of a PMTA TiAl alloy extruded at 1400 ° C. and annealed at 1000 ° C. for 2 hours. FIG. 1A shows the microstructure of PMTA-1, FIG. 1B shows the microstructure of PMTA-2, FIG. 1C shows the microstructure of PMTA-3, and FIG. 1D shows the microstructure of PMTA-4.

2A-D are 500-fold optical micrographs of PMTA alloys hot extruded at 1400 ° C. and annealed at 1000 ° C. for 2 hours. FIG. 2A shows the microstructure of PMTA-1, FIG. 2B shows the microstructure of PMTA-2, FIG. 2C shows the microstructure of PMTA-3, and FIG. 2D shows the microstructure of PMTA-4.

FIG. 3 shows the vanity-pattern bands observed on backscattering of PMTA-2 hot extruded at 1400 ° C. and annealed at 1000 ° C. for 2 hours, showing a non-uniform distribution of W. FIG.

Figure 4 shows the backscattering phase of PMTA-2 hot extruded at 1400 ° C. and annealed at 1000 ° C. for 2 hours.

5A is a 200-fold micrograph of PMTA-3 hot-extruded at 1400 ° C. and annealed at 1000 ° C. for 1 day, and FIG. 5B shows the same microstructure 500 times.

FIG. 6A is a 200-fold micrograph of PMTA-2 hot-extruded at 1400 ° C. and annealed at 1000 ° C. for 3 days, and FIG. 6B shows the same microstructure 500 times.

7A is an optical micrograph of a TiAl sheet (Ti-45Al-5Cr, atomic%) in a stored state, and FIG. 7B shows the same microstructure after annealing at 1000 ° C. for 3 days, all of which are 500 times photographs.

8A is a micrograph of PMTRA-6, and FIG. 8B is a micrograph of PMTA-7, all of which were extruded at 200 ° C. at 1380 ° C.

9A is a micrograph of PMTRA-6, and FIG. 9B is a micrograph of PMTA-7, all of which were extruded at 200 ° C. at 1365 ° C.

FIG. 10 is a micrograph showing the growth of abnormal grains in PMTA hot extruded at 1380 ° C. FIG.

11A-D are micrographs of PMTA-8 heat-treated at different conditions after hot extrusion at 1335 ° C. FIG. That is, FIG. 11A is heat treated at 1000 ° C. for 2 hours, FIG. 11B is 30 minutes at 1340 ° C., FIG. 11C is 30 minutes at 1320 ° C., and 11d is 30 minutes at 1315 ° C. (200 times).

FIG. 12 is a graph of resistivity versus temperature in microohms of samples 1 and 2 taken from an ingot having a composition of PMTA-4 nominal.

FIG. 13 is a graph of hemispherical total emissivity versus temperature for Samples 1 and 2. FIG.

14 is a graph of diffusivity versus temperature of samples 80259-1, 80259-2, and 80259-3 cut out from the same ingot as samples 1 and 2. FIG.

15 is a graph of the specific heat versus temperature of titanium aluminated according to the present invention.

16 is a thermal expansion vs. temperature plot of samples 80259-1H, 80259-1C, 80259-2H and 80259-3H and 80259-3C cut out from the same ingot as Samples 1 and 2. FIG.

According to a first aspect, the present invention provides a biphasic titanium aluminum alloy having a layered microstructure controlled by colony size. The alloy may be provided in various forms, such as in a cast, hot extruded, cooled and hot worked or heat treated state. As a final product, the alloy can be made of an electric resistance heating element having a specific resistance of 60 to 200 µΩ · cm. The alloy may include additional elements that provide microparticles, such as second phase or boride particles, to the clony boundary. The alloy may comprise a grain boundary equiaxed structure. Additional alloying elements may include, for example, up to 10 atomic percent of W, Nb and / or Mo. The alloy may be made from thin sheets having a yield strength of greater than 80 ksi (560 MPa), an ultimate tensile strength of greater than 90 ksi (630 MPa), and / or a tensile elongation of at least 1.5%. Aluminum may be present in an amount of 40-50 atomic%, preferably in an amount of about 46 atomic%. Titanium may be present in an amount of at least 45 atomic%, preferably at least 50 atomic%. For example, the alloy may include 45 to 55 atomic% Ti, 40 to 50 atomic% Al, 1 to 5 atomic% Nb, 0.5 to 2 atomic% W, 0.1 to 0.3 atomic% B. The alloy is preferably free of Cr, V, Mn and / or Ni.

The present invention provides two-phase TiAl alloys having thermo-physical and mechanical properties useful for a variety of applications such as resistive heating elements. The alloy exhibits useful mechanical properties and corrosion resistance at high temperatures up to 1000 ° C. at most. TiAl alloys can be made of sheet materials having extremely low density (about 4.0 g / cm ³ ), a preferred combination of tensile ductility and strength at room temperature and high temperature, high electrical resistance, and / or less than 10 mils in thickness. One use of such sheet materials is resistive heating elements in devices such as cigarette lighters and the like. For example, the sheet may be formed of a tubular heating element having a series of heating strips that individually power an ignition portion of a cigarette of an electric smoking device of the type described in US Pat. Nos. 5,591,368 and 5,530,225. In addition, the alloy may be free of elements such as Cr, V, Mn and / or Ni.

The tensile ductility of dual-phase TiAl alloys having a layered structure according to the present invention is comparable to TiAl alloys containing 1 to 4 atomic% Cr, V, and / or Mn to improve tensile ductility at ambient temperature. It can be controlled primarily by colony size rather than alloying elements. Therefore, the present invention provides a high strength TiAl alloy which may be free of Cr, V, Mn and / or Ni.

The nominal composition of the irradiated alloy whose base alloy is composed of Al 46.5 atomic% and balance Ti is shown in Table 1. Small amounts of alloying additives were added to investigate the effects on the mechanical and metallurgical properties of the two-phase TiAl alloys. The possible effects on oxidation resistance for up to 4% of Nb were investigated, the effects on microstructural stability and creep resistance for up to 1.0% of W were investigated, and up to 0.5% for Mo. The effect on high temperature fabrication was investigated. At most 0.18% of boron was added to refine the layered structure in the dual-phase TiAl alloy.

Eight alloys having the compositions shown in Table 1, identified as PMTA-1 to 9, were made into copper molds of 1 inch diameter by 5 inches long by arc melting and drop casting using commercially pure metals. All alloys were successfully cast without casting defects. Seven alloy ingots (PMTA-1 to 4 and 6 to 9) were placed in a Mocan and extruded at a high temperature of 1335 to 1400 ° C. with an extrusion ratio of 5: 1 to 6: 1. Extrusion conditions are shown in Table 2. The cooling rate after extrusion was controlled by quenching the extrusion rods in air and water for a short time. The alloy rods extruded at 1365-1400 ° C. had an irregular shape, while PMTA-8 hot extruded at 1335 ° C. showed a much smoother surface without surface irregularities. However, no crack was observed in any of the hot-extruded alloy rods.

The microstructure of the alloys was examined using optical metallography and electron super probe analysis during casting and in the heat treated state (Table 2). In the casting-state, the alloys all exhibited a layered structure with some degree of segregation and nuclear segregation. 1 and 2 are optical micrographs magnified 200 and 500 times, respectively, of the hot-extruded alloys PMTA-1 to 4, stress-relieved at 1000 ° C. for 2 hours. All alloys exhibited a fully layered structure with a small amount of equiaxed grain structures at the colony boundary. Some fine particles were observed at the colony boundary, which was identified as boride by electron microprobe analysis. In addition, there was no apparent difference in microstructural characteristics among these four PMTA alloys.

Electron microprobe analysis shows that tungsten is not evenly distributed even in hot extruded alloys. As shown in FIG. 3, the vanity pattern band at darker contrast shows a decrease of about 0.33 atomic% of W. 4 shows the formation of particles of the second phase (borides) at bright contrast of the colony boundary onto the backscattering phase of PMTA-2. The composition of the boride was determined and shown in Table 3 together with the composition of the layered matrix. The particles of the second phase are essentially (Ti, W, Nb) borides, which are decorated and fixed layered colony boundaries.

5 and 6 show optical microstructures of hot extruded PMTA-3 and 2 annealed at 1000 ° C. for 1 day and 3 days, respectively. The grain boundary equiaxed structure was clearly observed in specimens annealed for a long time and its amount increased with annealing time at 1000 ° C. There is a significant amount of equiaxed grain structure in the specimen annealed at 1000 ° C. for 3 days.

For comparison purposes, a 9 mil thick TiAl sheet (Ti-45Al-5Cr, atomic%) was evaluated. FIG. 7 shows the optical microstructure of the TiAlCr sheet in both the stored and annealed state (3 days at 1000 ° C.). In contrast to the dual-phase layered structure of the alloy according to the invention, the TiAlCr sheet has a double structure and its grain structure does not exhibit significant roughness at 1000 ° C.

Tensile sheet specimens with a thickness of 9-20 mils and a gauge length of 0.5 inch were annealed at 1000 ° C. for 2 hours using an EDM machine and then cut from hot extruded alloy rods. Some of the specimens were reannealed at 1000 ° C. for up to 3 days before tensile testing. Tensile testing was performed using an Instron test machine at a strain rate of 0.1 inch / second at room temperature. Table 4 summarizes the tensile test results.

All of the stress-relieved alloys at 1000 ° C. for 2 hours all exhibited tensile elongation of at least 1% in air at room temperature. Tensile elongation was unaffected at 9 to 20 mils thick. As shown in Table 4, alloy PMTA-4 of the four alloys showed the best tensile ductility. It should be noted that the 1.6% tensile elongation from a 20 mil thick sheet specimen is equivalent to a 4% elongation from a bar specimen with a gauge diameter of 0.12 inches. Tensile elongation seems to increase somewhat with annealing time at 1000 ° C and maximum ductility is obtained when the specimen is annealed at 1000 ° C for 1 day.

The alloys are all exceptionally strong and have a yield strength of at least 100 ksi (700 MPa) and ultimate tensile strength of at least 115 ksi (800 MPa) at room temperature. The high strength is due to the refined fully layered structure produced in this TiAl alloy. In comparison, the TiAlCr sheet material has a yield strength of only 61 ksi (420 MPa) at room temperature. Therefore, PMTA alloy is 67% stronger than TiAlCr sheet. PMTA alloys containing 0.5% Mo show significantly increased strength but have a slightly lower tensile elongation at room temperature.

8A-B and 9A-B show optical micrographs of PMTA-6 and 7 hot extruded at 1380 ° C. and 1365 ° C., respectively. The alloys all exhibit a layered grain structure with little internal colony structure. Large colony grains (see FIG. 10) were observed in both hot extruded alloys at 1380 ° C. and 1365 ° C., possibly due to abnormal grain growth in alloys containing low concentrations of borane after hot extrusion. There was no significant difference in microstructure characteristics between these two PMTA alloys.

Figure 11a-d shows the effect of heat treatment on the microstructure of the high-temperature extruded PMTA-8 at 1335 ℃. The alloy extruded at 1335 ° C exhibits much finer colony size and much more internal colony structure compared to the alloys hot extruded at 1380 ° C and 1365 ° C. Heat treatment at 1000 ° C. for 2 hours did not result in any significant change in the extruded structure (FIG. 11A). However, heat treatment at 1340 ° C. for 30 minutes produced substantially larger colony structures (FIG. 11B). Lowering the heat treatment temperature from 1340 ° C. to 1320-1315 ° C. (with a difference of 20-25 ° C.) drastically reduced the colony size as shown in FIGS. 11C and 11D. Annealing at 1320-1315 ° C. also appears to produce more internal colony structures in PMTA-8. Abnormal grain growth was almost completely removed by hot extrusion at 1335 ° C.

Tensile sheet specimens of PMTA-6-8 having a thickness of 8 to 22 mils and a gauge length of 0.5 inch were subjected to final heat treatment at 1000 ° C. for 2 hours or 1320 to 1315 ° C. for 20 minutes using an EDM machine, followed by hot extrusion. Cut from the alloy rods. Tensile tests were performed using an Instron testing machine at a temperature of up to 800 ° C., a strain of 0.1 inch / second in air. All of the tensile test results are shown in Tables 5 to 8. Alloys PMTA-4, -6 and -7 heat treated at 1000 ° C. for 2 hours show good strength at all temperatures regardless of the hot extrusion temperature. Hot extrusion at 1400-1365 ° C. provides low tensile ductility (less than 4%) at room temperature and high temperature. A significant increase in tensile ductility was obtained at all temperatures when hot extruded at 1335 ° C. PMTA-8, hot-extruded at 1335 ° C., exhibited the highest strength and tensile ductility at all test temperatures. There were no systematic changes in tensile ductility in specimens with a thickness of 8 to 22 mils.

Tables 7 and 8 also show the tensile properties of PMTA-6 and 7 heat treated at 1320 ° C. and 1315 ° C. for 20 minutes, respectively. Compared with the result obtained after the heat treatment at 1000 ° C., the heat treatment at 1320 to 1315 ° C. increased the tensile elongation but decreased the strength at the test temperature. Of all the alloys and heat treatments, PMTA-8 hot extruded at 1335 ° C. and annealed at 1315 ° C. for 20 minutes showed the best tensile ductility at room temperature and high temperature. The alloy exhibited tensile ductility of 3.3% and 11.7% at room temperature and 800 ° C., respectively. PMTA-8, heat treated at 1315 ° C., was found to be substantially stronger than known TiAl alloys.

In an attempt to demonstrate the flexural ductility of the TiAl sheet material, several pieces of 11-20 mil PTMA-7 and PTMA-8 alloy sheets produced by hot extrusion and heat treatment at 1320 ° C. were bent at room temperature. Each alloy piece was not broken after bending to 42 °. These results clearly show that PTMA alloys with controlled microstructures can be bent at room temperature.

The oxidation mode was studied by exposing PMTA-2, -5 and -7 sheet samples (thickness 9-20 mils) in air at 800 ° C. Samples were periodically removed from the furnace and weighed and inspected for surfaces. The sample showed a very low weight increase without indicating cleavage. This indicates that the alloying additives of W and Nb affect the oxidation rate of the alloy at 800 ° C., and W is more effective in improving the oxidation resistance of the TiAl alloy. Among the alloys, PMTA-7 exhibited minimal mass increase and best oxidation resistance at 800 ° C. Oxidation of PMTA-7 indicates that the oxide scales are fully fixed without signs of fine cracking and spalling. This observation clearly suggests that the oxide scales formed at 800 ° C. adhere well to the base material and are very protective.

FIG. 12 is a graph of resistivity versus temperature in microohms for samples 1 and 2 cut out of an ingot with a nominal composition of PMTA-4, i.e. 30.8 wt% Al, 7.1 wt% Nb, 2.4 wt% W, 0.045 wt% B ego; 13 is a graph of hemispherical total emissivity versus temperature for Samples 1 and 2; 14 is a graph of diffusivity versus temperature of samples 80259-1, 80259-2, and 80259-3 cut out from the same ingot as Samples 1 and 2; 15 is a graph of the specific heat versus temperature of titanium aluminated according to the present invention; FIG. 16 is a graph of thermal expansion versus temperature of samples 80259-1H, 80259-1C, 80259-2H, 80259-3H, and 80259-3C cut out from the same ingot as Samples 1 and 2. FIG.

In summary, high-temperature PMTA alloys extruded at 1365-1400 ° C. exhibit predominantly layered structures with little internal colony structure, while PMTRA-8 extruded at 1335 ° C. shows much finer colony structures and more internal colony structures. After heat-treating PMTA-8 for 20 minutes at 1315-1320 degreeC, a fine layered structure is produced. The alloy may comprise borides (Ti, W, Nb) formed at the colony boundary. Moreover, tungsten in hot extruded alloys is not evenly distributed, suggesting the possibility of high electrical resistance of TiAl alloys containing W additives. The addition of 0.5 atomic% Mo significantly increases the yield strength and ultimate tensile strength of the TiAl alloy, but reduces the tensile elongation to some extent at room temperature. Of the four high-temperature extruded alloys PMTA 1-4, PMTA-4 with Ti 46.5 atomic%, Al 3 atomic%, Nb 0.5 atomic%, W 0.2 atomic% and B alloy composition is the best combination of tensile ductility and strength at room temperature Has Compared to TiAlCr sheet material (Ti-45 Al-5Cr), PMTA-4 is 67% stronger than TiAlCr sheet. In addition, while PMTA-4 had an elongation of 1.4%, TiAlCr sheets did not exhibit flexural ductility at room temperature. Tensile elongation of TiAl alloy is independent of sheet thickness in the range of 9 to 20 mils. Alloys PMTA 4, 6 and 7 heat-treated at 1000 ° C. for 2 hours exhibited excellent strength at temperatures of up to 800 ° C., regardless of the hot extrusion temperature. However, hot extrusion at 1400-1365 ° C. provides low tensile ductility (less than 4%) at room temperature and high temperature. A significant increase in tensile ductility is obtained at all temperatures when the extrusion temperature is 1335 ° C. PMTA-8 (Ti-46.5 Al-3 Nb-1W-0.5B), hot-extruded at 1335 ° C. and annealed at 1315 ° C. for 20 minutes, showed the best tensile ductility at room temperature and high temperature (3.3% at room temperature, 11.7% at 800 ° C).

Nominal alloy composition Subsidy (atomic%) Alloy number Ti Al Cr Nb Mo W B PMTA-1 50.35 46.5 0 2 0.5 0.5 0.15 PMTA-2 50.35 46.5 0 2 - 1.0 0.15 PMTA-3 49.85 46.5 0 2 0.5 1.0 0.15 PMTA-4 49.85 46.5 0 3 - 0.5 0.15 PMTA-5 47.85 46.5 0 4 - 0.5 0.15 PMTA-6 49.92 46.5 0 3 - 0.5 0.08 PMTA-7 49.92 46.5 0 3 - 1.0 0.08 PMTA-8 49.40 46.5 0 3 - 1.0 0.10 PMTA-9 49.32 46.5 0 3 - 1.0 0.18

Composition (% by weight) Alloy number Ti Al Cr Nb Mo W B PMTA-1 60.46 31.36 0 4.64 1.20 2.30 0.04 PMTA-2 59.80 31.02 0 4.60 - 4.54 0.04 PMTA-3 58.86 30.83 0 4.57 1.18 4.52 0.04 PMTA-4 59.55 31.19 0 6.93 - 2.29 0.04 PMTA-5 57.71 30.85 0 9.14 - 2.26 0.04 PMTA-6 59.56 31.20 0 6.93 - 2.29 0.02 PMTA-7 57.98 30.68 0 6.82 - 4.50 0.02 PMTA-8 57.98 30.68 0 6.82 - 4.50 0.02 PMTA-9 57.97 30.67 0 6.82 - 4.49 0.05

Fabrication and Heat Treatment Conditions Used for PMTA Alloys Alloy number Hot extrusion temperature (℃) Heat treatment (℃ / hour) PMTA-1 1400 1000 ℃, up to 3 days PMTA-2 1400 1000 ℃, up to 3 days PMTA-3 1400 1000 ℃, up to 3 days PMTA-4 1400 1000 ℃, up to 3 days PMTA-5 PMTA-6 1380, 1365 1000 ℃ / 2 hours PMTA-7 1380, 1365 1000 ° C./2 hours, 1320 ° C./20 minutes PMTA-8 1335 1000 ° C./2 hours, 1315 ° C./20 minutes

Phase Composition in PMTA-2 Alloy Determined by Electron Microprobe Analysis Alloy element (atomic%) Prize Ti Al W Nb Matrix phase (dark contrast) Remaining amount 44.96 0.82 1.32 Matrix phase (bright contrast) Remaining amount 44.70 1.15 1.32 Boride (metal elements only) 77.69 8.66 9.98 3.67

Tensile Properties of PMTA Alloy Extruded at 1400 ° C and Tested at Room Temperature Alloy number Composition Nb-Mo-W (Atom%) Tensile Elongation (%) σ _y (ksi) σ _μe (ksi) 2 hours / 1000 ℃ PMTA-1 2 / 0.5 / 0.5 1.0 114 118 PMTA-2 2/0 / 1.0 1.2 104 117 PMTA-3 2 / 0.5 / 1.0 1.1 123 132 PMTA-4 3/0 / 0.5 1.4 102 115 1 day / 1000 ℃ PMTA-3 2 / 0.5 / 1.0 1.4 115 131 3 days / 1000 ℃ PMTA-2 2/0 / 1.0 0.8 105 109

Tensile Properties of PMTA-4 Extruded at 1400 ° C. and Annealed at 1000 ° C. for 2 Hours Test temperature (℃) Yield strength (ksi) Ultimate tensile strength (ksi) % Elongation 22 102.0 115 1.4 600 101.0 127 2.4 700 96.5 130 2.7 800 97.8 118 2.4

Tensile Properties of PMTA-6 Extruded at 1365 ° C. and Annealed at 1000 ° C. for 2 Hours Test temperature (℃) Yield strength (ksi) Ultimate tensile strength (ksi) % Elongation 22 121.0 136 1.3 300 101.0 113 1.2 700 93.6 125 2.7 800 86.5 125 3.9

Tensile Properties of PMTA-7 Extruded at 1365 ℃ Test temperature (℃) Yield strength (ksi) Ultimate tensile strength (ksi) % Elongation Annealing at 1000 ° C for 2 hours 22 116.0 122 1.0 300 101.0 116 1.5 700 105.0 131 2.7 800 87.2 121 3.1 Annealed for 20 minutes at 1320 ° C 20 84.5 106.0 3.0 300 71.4 89.8 2.5 700 68.5 97.2 4.5 800 63.5 90.2 4.5

Tensile Properties of PMTA-8 Extruded at 1335 ℃ Test temperature (℃) Yield strength (ksi) Ultimate tensile strength (ksi) % Elongation Annealing at 1000 ° C for 2 hours 22 122.0 140 2.0 300 102.0 137 4.3 700 95.0 131 4.7 800 90.2 124 5.6 Annealed for 20 minutes at 1320 ° C 20 96.2 116 3.3 300 79.4 115 6.1 700 72.2 112 7.5 800 72.0 100 11.7

The titanium aluminate may be manufactured in various forms or products such as an electric resistance heating element. However, the compositions described herein can also be used for other purposes, such as thermal spraying applications, in which the composition can be used as a coating having oxidation or corrosion resistance. The compositions also include oxidation and corrosion resistant electrodes, furnace components, chemical reactors, sulfurized materials, corrosion resistant materials used in the chemical industry, coal slurry or coal tar conveying pipes, substrate materials for catalytic converters, exhaust walls for automotive and diesel engines, and It can be used for turbocharger rotors, porous filters and the like.

For resistive heating elements, the geometry of the heating element blades can be changed according to the following equation to optimize the heater resistance: R = ρ (L / W × T), where R is the resistance of the heater, ρ is the heater material The resistivity of L is the length of the heater, W is the width of the heater and T is the thickness of the heater. The specific resistance of the heater material can be changed by a change in the composition such as the adjustment of the aluminum component in the heater material, or by mixing the alloy additives. For example, the resistivity can be significantly increased by mixing alumina particles in the heater material. The heater material may optionally include ceramic particles to increase creep resistance and / or thermal conductivity. For example, heater materials may be nitrides of transition metals (Zr, Ti, Hf), carbides of transition metals, borides of transition metals, and MoSi for the purpose of providing good high temperature creep resistance and good oxidation resistance at up to 1200 ° C. _It may comprise particles or fibers of a conductive material such as _two . The heater material may also have a heater material creep resistance at high temperatures, and also for improving the thermal conductivity and / or reducing the coefficient of thermal expansion of the heater material, such as Al ₂ O ₃ , Y ₂ O ₃ , Si ₃ N ₄ , ZrO _2, etc. Particles of the electrically insulating material can be mixed. Electrically insulating / conductive particles / fibers may be added to the powder mixture of Fe, Al, Ti or iron aluminide, or such particles / fibers may be formed by the synthesis reaction of an elemental powder exothermic during manufacture of the heater element. Can be.

The principles, preferred embodiments, and implementation methods of the present invention have been described so far. However, the invention is not limited by the specific embodiments described herein. Therefore, the above embodiments should be considered illustrative rather than limiting, and it should be understood that modifications may be made to the embodiments by those skilled in the art without departing from the scope of the invention as defined in the following claims.

Claims (19)

An aluminated titanium alloy consisting essentially of 50 to 65 weight percent Ti, 25 to 35 weight percent Al, 2 to 15 weight percent Nb, less than 5 weight percent Mo, 1 to 10 weight percent W, and 0.01 to 0.2 weight percent B. The aluminized titanium alloy according to claim 1, which is in a cast, hot extrusion, cooling operation, or heat treatment state. The aluminized titanium alloy of claim 1, wherein the alloy has a two-phase layered microstructure in which fine particles are located at the colony boundary. 4. The aluminated titanium alloy of claim 3, wherein the fine boride particles are located at the colony boundary. 4. The aluminized titanium alloy of claim 3, wherein the fine second phase particles are located at the colony boundary. The aluminized titanium alloy according to claim 1, wherein the alloy has a two-phase microstructure comprising a grain boundary equiaxed structure. The Ti content is 57 to 60%, Al content 30 to 32%, Nb content 4 to 9%, Mo content 2%, W content 2-8% and B content 0.02 ~ 0.08% titanium aluminate alloy. The aluminized titanium alloy of claim 1, wherein the yield strength is greater than 80 ksi (560 MPa), the ultimate tensile strength is greater than 90 ksi (680 MPa), and / or the tensile elongation is at least 1%. The aluminized titanium alloy according to claim 1, wherein the alloy has a microstructure in which W is nonuniformly distributed. The aluminized titanium alloy according to claim 1, wherein aluminum is present in an amount of 46 to 47 atomic percent. The aluminized titanium alloy of claim 1, wherein the alloy has a layered microstructure that is substantially free of equiaxes at the colony boundary. The aluminized titanium alloy of claim 1, wherein the alloy does not comprise Mo or Cr. The aluminized titanium alloy according to claim 1, wherein the Ti content is 57 to 60%, the Al content is 30 to 32%, the Nb content is 4 to 9%, the W content is 2 to 8% and the B content is 0.02 to 0.08%. . The aluminized titanium alloy according to claim 1, comprising Ti 45-55 atomic%, Al 40-50 atomic%, Nb 1-5 atomic%, W 0.3-1.5 atomic%, and B 0.1-0.3 atomic%. The aluminized titanium alloy according to claim 1, which is composed of a sheet having a thickness of 8 to 30 mils. The aluminized titanium alloy of claim 1, which is free of Cr, V, Mn, Co, Cu, and Ni. The aluminized titanium alloy according to claim 1, which is made of TiAl having 2 to 4 atomic% Nb, 1 atomic% or less Mo, and 0.5 to 2 atomic% W, 0.1 to 0.3 atomic% B. The aluminized titanium alloy according to claim 1, comprising from 1 to 4 atomic percent Nb, up to 1 atomic percent Mo, and from 0.25 to 2 atomic percent W. The aluminization of claim 1, wherein the alloy is formed of an electrical resistance heating element capable of heating from less than one second to 900 ° C. when passing a voltage of 10 volts at a maximum and 6 amps of current at a maximum through the heating element. Titanium alloy.