Method of thermo-mechanical treatment of two-phase titanium alloys

FIELD: mechanical engineering; aircraft engine manufacture and medicine.

SUBSTANCE: proposed method consists in thermo-mechanical treatment accompanied by change in mechanical properties of material. Proposed method includes intensive plastic deformation of blank in crossing vertical and horizontal channels at temperature of 600°C and stored logarithmic degree of deformation no less than 2. After intensive plastic deformation in crossing channels, blank is subjected to extrusion by several passes at temperature of 300°C and drawing coefficient no less than 1,2.

EFFECT: enhanced strength characteristics of titanium alloys (ultimate strength, yield point, fatigue range) at retained satisfactory ductility.

1 tbl, 1 ex

 

The invention relates to thermo-mechanical processing with the change of the mechanical properties of the material and can be used in mechanical engineering, aircraft engine industry and medicine in the manufacture of semi-finished products of two-phase titanium alloys.

Known methods of processing two-phase titanium alloys to improve their strength properties.

For example, the mode of deformation of the workpieces in overlapping horizontal and vertical channels (see Wmel, Vigaplus, Viesnica "a plastic structure formation metals", Minsk: Nauka and Technica, 1994, p.26) allows you to consolidate the metal due to the intense shear strain.

A method of processing workpieces, including severe plastic deformation of the blank in overlapping horizontal and vertical channels pressurized in the latter, which is performed at the initial and final stages of the deformation process (patent RF N 2139164, the IPC 21 J 5/00, publ. 10.10.1999,).

There is a method of deforming the workpiece in the intersecting vertical and horizontal channels at a temperature of 600°With (To S.Y., Jang BC, Tires DH, Li S. Effect of temperature and initial microstructure on equal channel angular extrusion alloy Ti-6Al-4V. Script, materialia, No. 48, 2003, s-202).

Known methods do not allow poluchatelyam strength characteristics, including indicators of fatigue.

The closest to the invention is a method of deforming the workpiece in the intersecting vertical and horizontal channels at a temperature of 600° (Yapici GG, Karaman, I., Z.P. Luo, Rivers, Microstructure and mechanical properties of powder alloy Ti-6Al-4V intensely deformed using equal-channel angular pressing. Script, materialia, No. 49, 2003, s-1027).

This method can be used to enhance the strength characteristics of the processed material, but insufficient for use in critical structures.

The invention is aimed at improving the strength characteristics of two-phase titanium alloys while maintaining plasticity, including the massive blanks.

This object is achieved by a method of obtaining ultrafine-grained billets, including severe plastic deformation of the blank in overlapping vertical and horizontal channels at a temperature of 600°With accumulated logarithmic degree of deformation e≥2. Unlike the prototype after severe plastic deformation perform extrusion in several cycles at a temperature of 300°With drawing ratio not less than 1.2.

Extrusion used after severe plastic deformation in peresekajushihsya the vertical and horizontal channels, allows you to create a strain pattern, similar to the conditions of all-round compression that provides increased deformability of such hard materials, such as two-phase titanium alloys. For example, processes such as drawing or rolling under the same temperature and time conditions and degrees of deformation can not provide the high deformability of the materials due to the implementation of less favourable for its improvement schemes deformation. In this regard, the combination of intensive plastic deformation in an intersecting channels and extrusion in these modes provides additional refinement of the structure in the blanks, resulting in improved strength characteristics while maintaining ductility.

The method is as follows.

Preparation of two-phase titanium alloy in the form of a rod subjected to intense plastic deformation in the intersecting channels. The deformation is carried out at a temperature of 600°in several successive passes, between which the rod rotate around the longitudinal axis by 90°. The number of passes is determined by the accumulated achievement of the logarithmic strain e≥2.

After deformation in an intersecting channels, the workpiece is subjected to the edit processing on a lathe to remove the defective layer.

On the trail the next step, the workpiece is subjected to extrusion in a few cycles with a gradual decrease in diameter and increase the length of the workpiece with a set of drawing ratio 1, 2. The temperature of extrusion 300°was determined empirically and is a temperature at which the billet is formed ultrafine-grained structure that provides a combination of properties: high strength characteristics while maintaining ductility. After this stage they control the mechanical properties in tension at room temperature and the control of the microstructure.

Specific example

Took the rod of the alloy Ti-6A1-4V with a diameter of 40 mm and a length of 120 mm Rod was subjected to plastic deformation by the above method. The angle of intersection of the channels f=120°. Temperature deformation 600°C. the Number of consecutive passes of n=4. After editing and processing on a lathe, the workpiece diameter was 36 mm

In the next step, the rod was subjected to extrusion at a temperature of 300°C. the Number of cycles of extrusion was 6, resulting in the workpiece diameter is reduced from 36 to 20 mm, and the length of the workpiece is increased from 120 to 300 mm Control mechanical properties of the alloy in tension at room temperature showed the values shown in table 1. For comparison, table 1 shows the mechanical properties of the alloy front of thermomechanical processing on the proposed method, and properties after processing by a known method prototype.

table width="90%" border="1" cellpadding="0" cellspacing="0" frams="all"> Table 1The mechanical properties of the alloy Ti-6Al-4V in different StatesMechanical properties of alloyStatus alloyBefore processing, the proposed methodAfter processing by the method prototypeAfter treatment by the proposed methodTensile strength, MPa94012841350Yield strength, MPa84010421300Elongation, %16711Relative narrowing, %453537

Thus, the proposed method of thermomechanical processing of two-phase titanium alloys can significantly improve the strength characteristics of the processed material while maintaining satisfactory ductility.

The method of thermomechanical processing of two-phase titanium alloys, including severe plastic deformation of the blank in overlapping vertical and horizontal channels at a temperature of 600°With accumulated logarithmic degree of deformation of at least two, wherein the donkey intensive plastic deformation in an intersecting channels carry out the extrusion billet in multiple passes at a temperature of 300° With the drawing ratio not less than 1.2.



 

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SUBSTANCE: proposed method is accompanied by change in physico-mechanical properties of metal. Proposed method of production of ultra-fine-grain titanium blanks includes intensive plastic deformation of blanks in crossing vertical and horizontal channels at temperature of 500-250°C and thermo-mechanical treatment. Thermo-mechanical treatment including annealing and deformation is performed before intensive plastic deformation at stored logarithmic degree of deformation no less than 4.5; annealing is carried out at temperature not above temperature of polymorphous transformation minus 200°C; thermo-mechanical treatment is started at annealing temperature which is reduced in stepwise manner to temperature of intensive plastic deformation. Ultra-fine-grain structure is formed at lesser number of technological passes.

EFFECT: improved strength characteristics; reduced labor consumption; enhanced efficiency.

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1 ex

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FIELD: non-ferrous metallurgy; methods of titanium alloy bricks production.

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7 cl, 7 dwg, 21 tbl, 2 ex

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