High-temperature high-strength TiAl-Nb monocrystal and preparation method thereof

A tial-nb, high-strength technology, applied in the field of high-temperature and high-strength TiAl-Nb single crystal and its preparation, can solve the problems of high-temperature mechanical property testing without high-Nb-TiAl single crystal, reducing the mechanical properties of the alloy, affecting the mechanical properties, etc. Universal applicability and promotion value, improving high-temperature mechanical properties, and the effect of simple preparation process

Inactive Publication Date: 2015-09-02
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Since the traditional method of preparing high Nb-TiAl single crystal is Bridgman directional solidification, the crucible protective coating will diffuse into the alloy melt, forming impurities and affecting the mechanical properties
Preparation of single crystal in optical floating zone can avoid this shortcoming, but its temperature gradient is small and the success rate of preparation is low, so there is no high-temperature mechanical performance test of high-Nb-TiAl single crystal
In addition, Nb element is a β-phase stable element, too high Nb element will cause more residual segregation phase at room temperature in the directionally solidified sample, and the segregation phase is a brittle phase rich in Nb and less in Al, which will reduce the mechanical properties of the alloy

Method used

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  • High-temperature high-strength TiAl-Nb monocrystal and preparation method thereof
  • High-temperature high-strength TiAl-Nb monocrystal and preparation method thereof
  • High-temperature high-strength TiAl-Nb monocrystal and preparation method thereof

Examples

Experimental program
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Effect test

Embodiment 1

[0026] (1) The atomic percentage of the selected alloy composition is: Ti-45Al-8Nb-0.3C-0.2Si, the balance is Ti, and the initial raw materials are 99.999% high-purity Al, Ti, C and Si and 99.95% high-purity Ti in The water-cooled copper crucible electromagnetic induction suspension melting furnace repeatedly smelts TiAl-Nb button master alloy ingots four times;

[0027] (2) A Φ6mm round rod-shaped alloy was obtained by a differential suction casting method with a pressure difference of 3MPa.

[0028] (3) The optical floating zone method is used for directional solidification, the lower end is a 20mm seed rod, and the upper end is a 150mm feeding rod, and the feeding rod is necked and selected. During directional solidification, first install the feeding rod and the seed rod. The feeding rod and the seed rod must be kept coaxial and perpendicular to the horizontal plane. At the center; the protective gas with a flow rate of 4L / min is introduced, and the seed rod and the feedi...

Embodiment 2

[0032] Adopt the method same as embodiment 1 to prepare Ti-45Al-8Nb-0.4C-0.5Si, the alloy that the balance is Ti, but change and adopt the gravity casting method to obtain the round rod-shaped sample of Φ8mm, because adopt the necking crystal selection process, The alloy with this diameter can also quickly obtain a single crystal sample. After the same desegregation heat treatment, the tensile strength is 618MPa, and the elongation is 9.2%.

Embodiment 3

[0034] Adopt the same preparation method as Example 1, change the alloy composition to be Ti-45Al-8Nb-0.4Si-0.6C, and the balance is Ti (atomic percentage), also adopt the same heat treatment process, because a small amount of C and Si do not greatly The magnitude changes the phase transition temperature point, but brings high temperature strengthening effect, so that the tensile yield strength of the material at 900 ° C is 650 MPa, and the plastic strain is 7.6%.

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Abstract

The invention discloses a high-temperature high-strength TiAl-Nb monocrystal and a preparation method thereof. Based on the atomic percent, the high-temperature high-strength TiAl-Nb monocrystal comprises the alloy components: Ti-(43-47) Al-(6-10)Nb-(0.1-1)(C, Si), and the balance of Ti. The preparation method comprises the following steps: smelting TiAl-Nb button-shaped master alloy ingot casting by using an electro-magnetic induction suspension method; preparing a cylindrical rod-shaped sample by means of differential pressure suction casting or gravity casting; directionally condensing the cylindrical bar by using an optical float-zone crystal growth system to guarantee that the heating power is between 65% and 70%, the growth velocity is 5-30mm / h, the relative rotation speed is 20-40r / min and the argon flow protection is carried out for 3-5L / min; finally obtaining a TiAl-Nb monocrystal test bar; and performing desegregation heat treatment on the TiAl-Nb monocrystal bar to finally obtain the monocrystal test sample. By adopting the TiAl-Nb monocrystal alloy material prepared by using preparation method disclosed by the invention, the alloy pollution caused by a traditional Bridgman directional condensation method can be effectively avoided, a solid-liquid interface shape during condensation is controlled by regulating the heating power so as to quickly obtain the TiAl-Nb monocrystal, and after the desegregation of the TiAl-Nb monocrystal, the high-strength TiAl-Nb monocrystal alloy of which the yield strength is 637MPa at a temperature of 900 DEG C, the elongation percentage is 8.1% and the ductile-brittle transition temperature is not lower than 900 DEG C can be obtained.

Description

technical field [0001] The invention belongs to the technical field of lightweight high-strength structural materials, and in particular relates to a high-temperature high-strength TiAl-Nb single crystal and a preparation method thereof. Background technique [0002] TiAl alloy has the advantages of low density, high specific strength, good high temperature performance and excellent oxidation resistance. It is the best candidate material for aerospace high temperature applications, especially for engines, with grams as the unit of weight reduction. GE Company of the United States successfully used Ti-48Al-2Cr-2Nb (4822) alloy to develop the rear two-stage low-pressure turbine blade of the Boeing aircraft, which reduced the weight of the aircraft by about 200Kg. Compared with conventional TiAl alloys, high Nb-TiAl alloys can significantly improve their oxidation resistance and creep resistance. Due to the high melting point of Nb, the use temperature of the alloy can be incre...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C30B29/52C30B13/00C22C14/00
Inventor 陈光祁志祥彭英博郑功王敏智李沛
Owner NANJING UNIV OF SCI & TECH
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