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

A heat treatment method and alloy-based technology, which is applied in the field of intermetallic compounds, can solve problems such as uneven distribution of alloying elements, unfavorable alloy mechanical properties, and increased segregation severity, and achieve small grain size, simple high-temperature annealing heat treatment process, The effect of reducing the processing cost

Inactive Publication Date: 2007-08-22
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 the composite of vacuum self-consumption + self-consumption solidified shell is adopted Smelted by smelting process. Figures 1 and 2 show the original microstructure of the alloy sample before heat treatment. It can be seen from the figure that the large-scale cast high-niobium TiAl-based alloy is composed of γ / α 2 Near-lamellar structure composed of lamella clusters and a small amount of γ and β (B2) grains distributed between the lamella clusters. According to the previous research of our research group, there are three kinds of segregation in the alloy structure, which are respectively defined as: S-segregation (the arrow in Figure 2 has pointed out several areas: black contrast), β-segregation and α-segregation (as shown in Fig. 3), their presence greatly reduces the mechanical properties of the alloy.

[0017] P...

Embodiment 2

[0020] Put the alloy sample with the same alloy structure as in Example 1 and the size is 40 × 40 × 40 mm in a crucible and put it into a heat treatment furnace with a furnace temperature of 1350 ° C for 30 hours, then take out the sample and put it into the furnace immediately. Keep the temperature in a heat treatment furnace at 1050°C for 45 minutes, and finally take out the sample and cool it to room temperature in air. Observe the evolution process of the tissue at different times of incubation.

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

Embodiment 3

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

[0024] The experimental results show that the alloy sample can obtain a uniform full lamellar structure at 1370 ° C for 18 hours, 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 metal materials, and in particular provides a heat treatment method for optimizing the structure of a large-scale cast high-niobium TiAl-based alloy to obtain a fine and uniform full-lamellar structure. Background technique [0002] High-niobium TiAl-based intermetallic compounds use the addition of high-melting point refractory metal Nb 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 the Antioxidant. It has great advantages: the use temperature is 60-100°C higher than that of ordinary γ-TiAl-based intermetallic compounds, and the room temperature strength is 300-500MPa higher than that of ordinary γ-TiAl-based alloys. Comparable, while only half the density, almost 50% less weight. Its o...

Claims

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Application Information

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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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