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A tial single crystal alloy with fully controllable lamellar orientation and its preparation method

An orientation and lamellar technology, applied in the field of TiAl single crystal alloy and its preparation, can solve the problem of ignoring the solid-state phase transformation process, and achieve the effect of avoiding uneven composition and performance and simplifying the process.

Active Publication Date: 2017-06-27
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

So far, the research on the orientation control of TiAl sheets has focused on the solidification process, while ignoring the solid-state phase transition process after solidification.

Method used

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  • A tial single crystal alloy with fully controllable lamellar orientation and its preparation method
  • A tial single crystal alloy with fully controllable lamellar orientation and its preparation method
  • A tial single crystal alloy with fully controllable lamellar orientation and its preparation method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0036] The alloy composition used in the experiment is Ti 47 Al 45 Nb 8(atomic percentage at%), the purity of its metal components is 99.999%, under the protection of high-purity Ar gas, the master alloy is melted by cold crucible electromagnetic levitation melting equipment under the vacuum degree of 5 × 10-3Pa. A uniform master alloy ingot was obtained after 4 times of smelting, and suction-cast into a Φ4×100mm master alloy bar. Put the TiAl alloy test rod into a corundum crucible coated with high-purity yttrium oxide for directional solidification experiment, vacuumize to 5×10-3Pa, and then fill the system with 0.05MPa high-purity argon protective gas. , adjust the power of the induction power supply to heat the sample, the holding temperature is 1550K, the holding time is 25min, the directional solidification starts, and the growth rate of the directional solidification is controlled to be 5μm / s; when the drawing length reaches the sample length of 50mm, the rapid quench...

Embodiment 2

[0039] Using the same alloy composition and method as in Example 1, the holding temperature is 1550K, the holding time is 25min, and the directional solidification is started, and the growth rate of the directional solidification is controlled to be 15 μm / s; Figure 4 (a) and Figure 4 As shown in (b), at this pulling rate, the β→α solid-state phase transition retains the α phase with a 45° lamellar orientation, so the final structure is a single crystal with a 45° lamellar orientation.

[0040] Figure 5 The microstructure of the directional solidification competition segment at 15 μm / s. At this pulling rate, the driving force of the 45° grain solid phase deformation nucleus is greater than that of the 0° grain, so that the 0° grain cannot grow, and a TiAl alloy single crystal with a lamellar orientation and a growth direction of 45° is obtained.

Embodiment 3

[0042] Using the same alloy composition and method as in Example 1, the holding temperature is 1550K, the holding time is 25min, and the directional solidification is started, and the directional solidification growth rate is controlled to be 20 μm / s; Figure 6 (a) and Figure 6 As shown in (b), a single crystal with a lamellar orientation at 45° to the growth direction was obtained.

[0043] Figure 7 The solid-liquid interface retained for rapid quenching has a 4-fold symmetry of dendrite growth, with relatively obvious secondary dendrites and a 90° vertical relationship with the primary dendrite stem. It can be inferred that during the directional solidification process, The β phase of the cubic crystal system is the primary phase.

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Abstract

The invention discloses a lamellar orientation completely controllable TiAl intermetallic compound single crystal and a preparation method thereof. The material composition expression formula of the TiAl alloy provided by the invention is TiaAlbNbc (atomic percent), wherein a is greater than or equal to 42 and smaller than or equal to 55, b is greater than or equal to 43 and is smaller than or equal to 49, c is greater than or equal to 2 and is smaller than or equal to 9, and a+b+c=100. The preparation method of the controllable lamellar orientation TiAl single crystal alloy provided by the invention includes: conducting electromagnetic induction levitation melting of a TiAl alloy master ingot in a water-cooled copper crucible, and carrying out suction casting to obtain a directionally solidified bar; putting the bar into a high purity corundum crucible with an inner wall sintered with a high-purity yttrium oxide coating to perform Bridgman directional solidification; and changing solidification parameters to control the solid-state phase transformation process so as to make the single crystal lamellar orientation completely controllable and acquire the TiAl intermetallic compound single crystal with the lamellar orientation parallel to the growth direction.

Description

technical field [0001] The invention belongs to the technical field of intermetallic compound materials, and in particular relates to a TiAl single crystal alloy with fully controllable lamellar orientation and a preparation method thereof. Background technique [0002] TiAl intermetallic compound is a new type of light-weight high-temperature structural material, its specific gravity is less than 50% of that of nickel-based superalloys, and it has high specific strength, high specific rigidity, corrosion resistance, wear resistance, high temperature resistance and excellent oxidation resistance. It is an ideal material to replace Ni-based superalloys due to its advantages such as creep resistance. [0003] The mechanical properties of fully lamellar TiAl alloys are closely related to their lamellar orientation. Through the research on the full-sheet polysynthetic twinned crystal PST (Polysynthetic twinned crystal) with a single orientation, it is found that its strength an...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C30B29/52C30B11/00
CPCC30B11/00C30B29/52
Inventor 陈光彭英博李沛郑功祁志祥王敏智
Owner NANJING UNIV OF SCI & TECH