Heat treatment process for large size as-cast high-Nb TiAl-base alloy to obtain complete lamellar structure

A heat treatment method and base alloy technology, applied in the field of intermetallic compounds, can solve the problems of increased segregation severity, unfavorable mechanical properties of alloys, uneven distribution of alloying elements, etc. Small particle size effect

Inactive Publication Date: 2009-06-17
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the key way to obtain good comprehensive mechanical properties is to obtain a fine and uniform full-lamellar structure. For high-niobium TiAl-based alloys, the addition of high-content Nb makes the alloy face more serious element segregation problems. In addition, due to the alloy ingot For large size, the distribution of alloying elements is more uneven, which also increases the severity of segregation. Experimental studies have shown that the existence of segregation is extremely unfavorable for obtaining a fine and uniform full-lamellar structure and improving the mechanical properties of the alloy.

Method used

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  • Heat treatment process for large size as-cast high-Nb TiAl-base alloy to obtain complete lamellar structure
  • Heat treatment process for large size as-cast high-Nb TiAl-base alloy to obtain complete lamellar structure
  • Heat treatment process for large size as-cast high-Nb TiAl-base alloy to obtain complete lamellar structure

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] The chemical composition of the alloy used in the experiment is Al: 45, Nb: 8.5, W: 0.2, B: 0.2, Y: 0.02, the balance is Ti (atomic percentage at.%), and a composite of vacuum consumable + condensed shell Smelted by smelting process. figure 1 with figure 2 The original structure of the alloy sample before heat treatment is shown. From the figure, it can be seen that the large-size as-cast high-niobium TiAl-based alloy is composed of γ / α2 lamellae and a small amount of γ and β distributed between the lamellae. (B2) Near-lamellar structure composed of grains. According to the previous research of this research group, there are three kinds of segregation in the alloy structure, which are defined as: S-segregation ( figure 2 The arrows in have pointed out several areas: black contrast), β-segregation and α-segregation (such as image 3 Shown), their presence greatly reduces the mechanical properties of the alloy.

[0017] Put an alloy sample with a size of 10×10×10 mm in a c...

Embodiment 2

[0020] Put the alloy sample with the same alloy structure and size of 40×40×40 mm in the crucible in the crucible and heat it for 30 hours in the heat treatment furnace at the furnace temperature of 1350℃, then take out the sample and put it into the furnace immediately. Keep the temperature in the heat treatment furnace at 1050°C for 45 minutes, and finally take the sample out and cool it to room temperature in the air. Observe the evolution process of the tissue at different times of heat preservation.

[0021] The experimental results show that the alloy sample can be kept at 1350°C for 30 hours to obtain a uniform full lamella structure, and the average grain size of the lamella cluster is 240 microns.

Embodiment 3

[0023] Put an alloy sample with the same alloy structure and size of 60×60×60 mm as in Example 1 in a crucible and put it in a heat treatment furnace at a furnace temperature of 1370°C for 18 hours, then take out the sample and immediately put it in the furnace temperature Keep the temperature in the heat treatment furnace at 1050°C for 45 minutes, and finally take the sample out and cool it to room temperature in the air. Observe the evolution process of the tissue at different times of heat preservation.

[0024] The experimental results show that the alloy sample can be kept at 1370℃ for 18 hours to obtain a uniform full-lamella structure, and the average grain size of the lamellar cluster is 185 microns.

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Abstract

The present invention belongs to the field of intermetallic compound technology and is especially heat treatment process for optimizing the structure of large size as-cast high-Nb TiAl-base alloy to obtain fine and homogeneous complete lamellar structure. The present invention features that alloy samples of sizes 10x10x10 mm to 60x60x60 mm are cut off from as-cast high-Nb TiAl-base alloy ingot, set into crucible, maintained inside a heat treatment furnace at 1350-1400 deg.c for 6-36 hr, maintained inside one other heat treatment furnace at 900-1050 deg.c for 30-60 min, and finally air cooled outside the furnace to room temperature. Thus treated alloy has fine and homogeneous complete lamellar structure, greatly increased available sizes and low treating cost.

Description

Technical field [0001] The invention belongs to the technical field of intermetallic compounds in metallic materials, and in particular provides a heat treatment method for how to optimize the structure of a large-size as-cast high-niobium TiAl-based alloy to obtain a fine and uniform full-layer structure. Background technique [0002] The high-niobium TiAl-based intermetallic compound uses the high melting point refractory metal Nb element to increase the melting point and ordering temperature of the alloy, as well as the stability of the high-temperature structure, reduce the diffusion and stacking fault energy, improve the high-temperature strength of the alloy, and improve Antioxidant. It has great advantages: the use temperature is 60~100℃ higher than the ordinary γ-TiAl-based intermetallic compound, the room temperature strength is 300~500MPa higher than the ordinary γ-TiAl-based alloy, the mechanical properties and the traditional Ni-based superalloy for the production of ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C30/00C22F1/16
Inventor 林均品许正芳徐向俊王艳丽张勇林志陈国良
Owner UNIV OF SCI & TECH BEIJING
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