CN108754371B - A preparation method for refining near-alpha high temperature titanium alloy grains - Google Patents

Abstract

A method for preparing refined near α high-temperature titanium alloy grains belongs to the technical field of titanium alloys and can solve the problem that the strength-plasticity-toughness matching performance of the existing near α high-temperature titanium alloy is low, low-temperature multi-pass single-roll angle rolling is carried out on an as-cast blank, a sample is cut out from the obtained forged blank and is subjected to rapid heat treatment in a α phase region or a α + β phase region, and then a near alpha high-temperature titanium alloy with α phase grain size lower than 2 mu m can be obtained.

Description

A preparation method for refining near-alpha high temperature titanium alloy grains

technical field

The invention belongs to the technical field of titanium alloys, and in particular relates to a preparation method for refining near-alpha high temperature titanium alloy crystal grains.

Background technique

Near-alpha high temperature titanium alloy is one of the key materials of modern aero-engines. It is mainly used as compressor disc blades and casings of aero-engines to reduce the mass of the engine and reduce the thrust-to-weight ratio. The performance requirements of high-temperature titanium alloys for engines are very demanding. It requires titanium alloy structural materials to have high specific strength, high specific stiffness, high toughness, high damage tolerance, and weldability. Excellent comprehensive performance matching. Since these performance indicators often contradict the requirements for the composition and microstructure of the material, simply improving the composition can no longer meet the leap-forward development of titanium alloys as structural materials in the direction of high speed, large size, and complex structure. , weapons, ships and other weapons and equipment, all load-bearing components, load-bearing bolts and other fasteners have put forward clear requirements for high-strength titanium alloys and ultra-high-strength titanium alloys. In recent years, traditional hot processing techniques such as forging, rolling and extrusion have been gradually used in titanium alloys to control and optimize their microstructure and properties, and to a certain extent, the simultaneous optimization of strength and plasticity has been achieved, but a large number of researches It has been proved that the traditional hot deformation process has disadvantages such as large power loss and unsatisfactory performance improvement effect in improving the microstructure and properties of titanium alloys. At present, it is still unable to break through the "bottleneck" of the development and application of titanium alloys, and a large number of studies have proved that the α-phase grains The size of the titanium alloy has a significant effect on the strength and plasticity of the titanium alloy. Refining the grain size of the α phase has been proved to effectively enhance the strength and plasticity of the titanium alloy. At the same time, a series of The rapid heat treatment has gradually gained the favor of researchers, and the rapid heat treatment has gradually been valued by people because it makes the grains have no time to grow and refines the grains in the short-term heat treatment process.

SUMMARY OF THE INVENTION

Aiming at the problem of low strength-plasticity-toughness matching of existing near-α high temperature titanium alloys, the present invention provides a preparation method for refining near-α high temperature titanium alloy crystal grains.

The present invention adopts following technical scheme:

A preparation method for refining near-alpha high temperature titanium alloy grains, comprising the following steps:

The first step is to determine the α+β/β transformation point of the near-α high temperature titanium alloy by metallographic method;

The second step, multi-pass single roll angle rolling at low temperature: rapid forging of nearly α high temperature titanium alloy at 300-400 °C below the α+β/β transformation point with a deformation amount of 70%, in order to obtain higher distortion energy, for the follow-up The precipitation of the grains provides more energy, and the deformation rate is 1mm/s; the sample after rapid forging is rolled at the same temperature, and the thickness of the sample is controlled at 1mm for single-roll angle rolling; use Wire-cut EDM Cut a sample with a length of 200mm and a width of 20mm from the rolled sample, and perform low-temperature multi-pass single-roll angle rolling at 300-400°C below the α+β/β transformation point;

The third step, rapid heat treatment near the α+β/β transformation point: the sample after low-temperature multi-pass single-roll angle rolling is cut to a certain size by EDM, and the samples are respectively 15 above the α+β/β transformation point. ℃, at the α+β/β phase transition point, and at 15°C below the α+β/β phase transition point for 2 minutes, then water quenched and cooled to room temperature.

The process of the low-temperature multi-pass single-roll angle rolling in the second step is as follows: first, the rolled near-α high-temperature titanium alloy sheet is subjected to hoop shear deformation in a high-pressure torsion machine, and the initial thickness of the sample is 1 mm. After the hoop shear deformation, the thickness is 0.96mm, and then the sample is subjected to equal channel angular extrusion, and the channel height is 1 mm, that is, the thickness of the sample after the equal channel angular extrusion is still 1 mm. Circumferential shear deformation and equal channel angular extrusion are successively performed in a high-pressure torsion machine.

The size of the sample cut in the third step is 60mm*15mm*1mm.

Since the deformation passes have an effect on the microstructure and mechanical properties of the samples, in order to avoid too many variables, three passes of single-roll angle rolling are used.

The beneficial effects of the present invention are as follows:

1. The present invention is different from the traditional thermal deformation process, through low-temperature multi-pass single-roll angle rolling, so that more twins and dislocations are obtained inside the grains, and these defects can store more distortion energy, Thereby, the recrystallization temperature is significantly reduced, recrystallization is promoted, and the refined recrystallized grains are retained by rapid heat treatment in the β phase region or the α+β phase region, so that it is too late to grow, thereby refining the β grains. In addition, in the subsequent process of cooling to room temperature, a large number of subgrains, twins and dislocations retained by the previous low-temperature multi-pass single-roller angle rolling hinder the movement of grain boundaries on the one hand, and can act as α phase on the other hand. The nucleation site will significantly refine the α grains to further improve the strength and shape of the titanium alloy.

2. The present invention can prepare a near-α high-temperature titanium alloy with fine β-grain structure and excellent strength-plasticity-toughness matching, and the processing method is suitable for industrial production.

3. The near-α high temperature titanium alloy obtained by the present invention can refine the grain size of the α phase to 1.2 μm, and the alloy under this size can obtain the best comprehensive mechanical properties, and its tensile strength can reach 1126.3MPa, yielding The strength can reach 1097.5 MPa, and the elongation can reach 18.6%.

Description of drawings

Fig. 1 is the SEM image of the sample with the rapid heat treatment temperature of 1030 ℃ in Example 1 of the present invention;

2 is a SEM image of a sample with a rapid heat treatment temperature of 1030° C. in Example 2 of the present invention;

FIG. 3 is a SEM image of a sample with a rapid heat treatment temperature of 1030° C. in Example 3 of the present invention.

Detailed ways

Example 1

In the first step, near α high temperature titanium alloy Ti-1100 (Ti–6Al–2.75Sn–4Zr–0.4Mo–0.45Si), the α+β/β transformation point was measured by metallographic method to be 1015℃;

The second step, low-temperature multi-pass single-roll angle rolling: the near-α high-temperature titanium alloy Ti-1100 ingot (φ60mm*40mm) prepared by the vacuum induction magnetic levitation melting furnace is subjected to the first step of rapid forging at 715 °C, and the deformation is 70%, and the deformation rate is 1 mm/s; the rapid forging sample is rolled at 715 °C, and the thickness of the sample is controlled at 1 mm; the length of the rolled sample is cut by wire electric discharge cutting: The sample with a width of 200mm and a width of 20mm is placed in a high-pressure torsion machine for multi-pass single-roll angle rolling at a low temperature of 715°C. The deformation of the above three steps is called a round of large plastic deformation. Since the deformation passes have an effect on the microstructure and mechanical properties of the sample, in order to avoid too many variables, three passes of single-roll angle rolling were used in this experiment;

The third step, rapid heat treatment near the α+β/β transformation point: cut the sample with a size of 60mm*15mm*1mm from the sample after the low-temperature multi-pass single-roller angle rolling by EDM wire cutting, respectively in Quickly heat to 1030°C, 1015°C, and 1000°C in a vacuum resistance furnace. After holding for 2 minutes, quickly put it in water and cool it to room temperature.

Finally, the mechanical properties measured by rapid heat treatment at different temperatures are shown in Table 1. The comprehensive mechanical properties obtained by rapid heat treatment at 1030 °C are better: the tensile strength is 1126.3 MPa, the yield strength is 1097.5 MPa, and the elongation can reach 18.6%. The α-phase grain size is 1.2 μm.

Table 1 Mechanical properties of different heat treatment conditions at deformation temperature of 715℃

Example 2

In the first step, near α high temperature titanium alloy Ti-1100 (Ti–6Al–2.75Sn–4Zr–0.4Mo–0.45Si), the α+β/β transformation point was measured by metallographic method to be 1015℃;

The second step, low-temperature multi-pass single-roll angle rolling: the near-α high-temperature titanium alloy Ti-1100 ingot (φ60mm*40mm) prepared by the vacuum induction magnetic levitation melting furnace is subjected to the first step of rapid forging at 615 °C, and the deformation is 70%, and the deformation rate is 1 mm/s; the rapid forging sample is rolled at 615 °C, and the thickness of the sample is controlled at 1 mm; the length of the rolled sample is cut by wire electric discharge cutting: The samples with a width of 200 mm and a width of 20 mm are placed in a high-pressure torsion machine for multi-pass single-roll angle rolling at a low temperature of 615 ° C. The deformation of the above three steps is called one round of large plastic deformation. Since the deformation passes have an effect on the microstructure and mechanical properties of the sample, in order to avoid too many variables, three passes of single-roll angle rolling were used in this experiment;

The third step, rapid heat treatment near the α+β/β transformation point: cut the sample with a size of 60mm*15mm*1mm from the sample after the low-temperature multi-pass single-roller angle rolling by EDM wire cutting, respectively in Quickly heat to 1030°C, 1015°C, and 1000°C in a vacuum resistance furnace. After holding for 2 minutes, quickly put it in water and cool it to room temperature.

Finally, the mechanical properties measured by rapid heat treatment at different temperatures are shown in Table 2. The comprehensive mechanical properties obtained by rapid heat treatment at 1015 °C are better: the tensile strength is 1197.9MPa, the yield strength is 1142.5MPa, and the elongation can reach 17.5%. The α-phase grain size is 2.2 μm.

Table 2 Mechanical properties of different heat treatment conditions at deformation temperature of 615℃

Example 3

In the first step, near α high temperature titanium alloy Ti-1100 (Ti–6Al–2.75Sn–4Zr–0.4Mo–0.45Si), the α+β/β transformation point was measured by metallographic method to be 1015℃;

The second step, low-temperature multi-pass single-roll angle rolling: the near-α high-temperature titanium alloy Ti-1100 ingot (φ60mm*40mm) prepared by the vacuum induction magnetic levitation melting furnace is subjected to the first step of rapid forging at 665 °C, and the deformation is 70%, and the deformation rate is 1 mm/s; the rapid forging sample is rolled at 665 °C, and the thickness of the sample is controlled at 1 mm; the length of the rolled sample is cut by wire electric discharge cutting: The samples with a width of 200 mm and a width of 20 mm are placed in a high-pressure torsion machine for multi-pass single-roll angle rolling at a low temperature of 665 ° C. The deformation of the above three steps is called one round of large plastic deformation. Since the deformation passes have an effect on the microstructure and mechanical properties of the sample, in order to avoid too many variables, three passes of single-roll angle rolling were used in this experiment;

The third step, rapid heat treatment near the α+β/β transformation point: cut the sample with a size of 60mm*15mm*1mm from the sample after the low-temperature multi-pass single-roller angle rolling by EDM wire cutting, respectively in Quickly heat to 1030°C, 1015°C, and 1000°C in a vacuum resistance furnace. After holding for 2 minutes, quickly put it in water and cool it to room temperature.

Finally, the mechanical properties measured by rapid heat treatment at different temperatures are shown in Table 3. The comprehensive mechanical properties obtained by rapid heat treatment at 1030 °C are better: the tensile strength is 1158.4 MPa, the yield strength is 1121.6 MPa, and the elongation can reach 18.2%. The α-phase grain size is 1.6 μm.

Table 3 Mechanical properties of different heat treatment conditions at deformation temperature of 665℃

Claims (2)

1. a preparation method of refining near α high temperature titanium alloy grain, is characterized in that: comprise the steps: The first step is to determine the α+β/β transformation point of the near-α high temperature titanium alloy by metallographic method; The second step, multi-pass single roll angle rolling at low temperature: rapid forging of nearly α high temperature titanium alloy at 300-400 °C below the α+β/β transformation point with a deformation amount of 70%, in order to obtain higher distortion energy, for the follow-up The precipitation of crystal grains provides more energy, and the deformation rate is adjusted to 1mm/s; the sample after rapid forging is rolled at the same temperature, and the thickness of the sample is controlled at 1mm for single-roll angle rolling; Use wire electric discharge cutting to cut a sample with a length of 200 mm and a width of 20 mm from the rolled sample, and perform low-temperature multi-pass single-roll angle rolling at 300-400 ° C below the α+β/β transformation point; the low temperature The process of multi-pass single-roll angle rolling is as follows: First, the rolled near-α high-temperature titanium alloy sheet is subjected to hoop shear deformation in a high-pressure torsion machine. The initial thickness of the sample is 1mm, and after hoop shear deformation The thickness is 0.96mm, and then the sample is subjected to equal channel angular extrusion, and the channel height is 1 mm, that is, the thickness of the sample after the equal channel angular extrusion is still 1 mm, and the hoop shear deformation experienced by the sample is equal to the same. Channel angular extrusion is carried out successively, all in a high-pressure torsion machine; The third step, rapid heat treatment near the α+β/β transformation point: the sample after low-temperature multi-pass single-roll angle rolling is cut by EDM wire to a sample with a size of 60mm*15mm*1mm, respectively at α+β/β After the temperature is kept at 15°C above the phase transition point, at the α+β/β phase transition point, and at 15°C below the α+β/β phase transition point for 2 minutes, water is quenched and cooled to room temperature. 2. a kind of preparation method of refining near α high temperature titanium alloy grains according to claim 1, is characterized in that: described in the second step, the low-temperature multi-pass single-roller angle rolling is 3-pass single-roller angle rolling .

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