Method for making high-strength foil of titanium

FIELD: plastic working of metals, possibly manufacture of thin high-strength foil of titanium.

SUBSTANCE: method comprises steps of multi-pass reversing cold rolling and vacuum annealing; repeating cycle; using as initial blank titanium blank with ultra-fine grain structure provided due to intensified plastic deformation by equal-duct angular pressing process; rolling at pitch 15 - 8% for achieving total deformation 70 - 86 % per one cycle; setting number N of cycles necessary for making foil with thickness h according to mathematical expression; realizing vacuum annealing, preferably at temperature 350 -360 C for 0.5 - 1 h. Invention provides possibilities for making titanium foil with thickness up to 10 micrometers.

EFFECT: enhanced strength characteristics of titanium foil of lowered thickness with the same technological platicity7777.

2 cl, 2 tbl

 

The invention relates to the processing of metals by pressure and can be used in the production of thin, high-strength foil of titanium.

Titanium and its alloys are to difficult-to-deform materials. The receipt foil of titanium and its alloys present significant challenges and requires mechanical and thermal processing at elevated temperatures [1-4].

Currently, much attention is paid to materials in which different ways formed ultrafine-grained (UMP) structure (grain size less than one micron). The interest in such materials due to their unique physico-chemical properties. In particular, they have high strength and corrosion resistance [4, 5]. However, a significant limitation of the possibilities of conducting the heat treatment of materials with UMP-structure is lowered temperature of recrystallization. For example, for titanium grade VT1-0 with UMP-structure obtained by the method of equal-channel angular pressing (pressing) [4], the recrystallization temperature is around 450°C. Thus, to preserve the superior intrinsic properties of titanium with UMP-structure [4, 5], it is necessary to conduct processing at temperatures below specified.

A method of obtaining titanium blanks with UMP-structure [RF patent №2175685, C 22 F 1/18, 000], includes plastic deformation in intersecting vertical and horizontal channels at a certain temperature, followed by thermomechanical processing alternation of cold deformation with the degree of 30-90% with intermediate and final annealing in the temperature range 250-500°C for 0.5 to 2 hours. This method allows you to receive a volume of titanium billets with UMP-structure (grain size 0.1 μm) for subsequent use in critical structures. This method is not aimed at obtaining foil of titanium. However, some modifications it can be used to obtain a titanium foil. The disadvantage of this method is the use of intermediate annealing in one cycle.

There are various ways to obtain a foil of titanium and its alloys. The most common method of rolling the foil of titanium [1] includes a multi-way reversing cold rolling, degreasing and intermediate vacuum annealing. This method of rolling allows you to get a foil of titanium with a thickness of 0.02-0.1 mm annealed billet thickness of 0.5-0.8 mm for 7-8 cycles with a total deformation per cycle 20-50%. One cycle includes degreasing the surface of the tape and obezbolivaiuscii vacuum annealing at a temperature of 600-750°C, holding for 2-5 hours. A disadvantage of the known methods for the and is this method is used obezbolivaiuscii vacuum annealing at high temperatures (600-750° (C) with long shutter speeds (2-5 hours). In addition made by this method titanium foil has a low strength characteristics.

The task of the invention is the expansion of technological capabilities through the use of the billets with UMP-structure and lower temperature annealing in the manufacture of titanium foil, as well as increasing the strength characteristics of the foil of titanium in reducing its thickness and maintaining the technological plasticity.

This technical result is achieved in that in the method of obtaining high strength foil of titanium, including one cycle of the following operations: multi-way reversing cold rolling and vacuum annealing, then the cycle is repeated, as the original piece used titanium with UMP-structure obtained by the influence of severe plastic deformation by the pressing method [5], and are rolling with step 15-8% to the total deformation 70-86% per cycle, the number of cycles (N)required to obtain foil of a thickness (h), calculated by the formula:

N=(lnhto-lnho)/ln(l-ε),

where N is the number of cycles,

ho- the original thickness of the blank,

hr- the final thickness of the foil,

ε - the average from oxytelinae deformation (degree of compression) for one cycle.

When this vacuum annealing is preferably carried out at a temperature of 350-360°C for 0.5-1 hour.

Use in the manufacture of foil blanks with UMP-structure (grain size ~0.6 μm), in which the deformation of the grain boundary pascalian observed already at room temperature [6], and small degrees of compression in one step (a step is considered to be the total rolling in both directions) allows to achieve without intermediate annealings total deformation at room temperature for one cycle 70-86%. Thus there is a reduction of the grain size and strength characteristics UMP-titanium increase and reach values of the relevant titanium alloys of the Ti-Al-V. Subsequent vacuum annealing at a temperature of 350-360°C for 0.5-1 hour leads to relaxation of internal stresses in titanium, as judged by the decrease in electrical resistivity (see drawing). When the grain size is not changed. The growth of grains in deformed UMP-titanium, and hence a significant reduction of physical and mechanical properties is observed after vacuum annealing at 400 to 450°, 1 hour. Vacuum annealing at temperatures smaller 350°do not remove internal stresses, which does not allow the next cycle to achieve without destroying the material, the total deformation at room temperature 70-86%.

Implementation of PR is degenova method provides the possibility of obtaining high strength foil of titanium to a thickness of 10 μm.

For assay of the present invention used titanium VT1-0 in two States: in coarse-grained (KS) factory supplied (the grain size of 5-10 microns) and UMP-state, formed from the KS-state method CMR-pressing (grain size ~0.6 μm). In detail this structure is described in [4]. Mechanical tensile properties of titanium VT1-0 in coarse and UMP-States are presented in tables 1 and 2.

For rolling of used rods titanium width 6mm, length 70 mm, the thickness was changed from 1000 to 4000 microns. Reverse rolling was carried out on a twin roll mill (roll diameter 80 mm, the rotation speed of 6 rpm) at room temperature with a step 15-8%. Deformation (degree of reduction) was calculated by the formula:

where h0the thickness of the blank to rolling, h is the thickness of the workpiece after rolling.

Upon reaching the total deformation 70-86% of the material was annealed in vacuum at a temperature of 350-360°0.5-1 hour, after which the cycle was repeated. Control of microstructure and mechanical properties of titanium was performed after rolling and after subsequent annealing.

In tables 1, 2 presents a description of the structure and mechanical properties of the foil of titanium in KS and UMP-States at different stages of processing (the original blank thickness was 3800 microns).

In the first cycle after the total reverse p is akadi 75% of the average grain size UMP-patterns decreased to ~of 0.15 μm. When this strength characteristics UMP-titanium has increased by 40%. Annealing at a temperature of 350°, 1 hour leads to a partial relaxation of internal stresses, as evidenced by a decrease in the tensile and yield (table 1) and values of electrical resistivity (ρ) laminated UMP-titanium (drawing). The grain size does not change.

In the following second, third and fourth cycles, the total deformation UMP-titanium, respectively, 70%, 86% and 75%.

Vacuum anneals were performed: in the second cycle at a temperature of 360°, 1 hour, when the third - 350°0.5 hour, the fourth at 350°With 1 hour. From the data table. 1 shows that these four cycles of treatment, the thickness of the sample source UMP-titanium is reduced, for example, from 3800 to ~10 µm. This UMP-structure in the material is not only preserved, but also becomes more dispersed, and its strength characteristics reach the relevant titanium alloy VT6 [1].

In coarse-grained titanium in the first cycle, the total degree of deformation -75% was achieved by reversing rolling with the step of 10-3%. In the titanium was formed inhomogeneous grain structure: about 70% of the surface area of the material occupied by the grain sizes of 0.1-0.5 μm and 30% of the square of the grain size of 5-10 microns. Vacuum annealing KS-titanium after the total deformation is 75% at a temperature of 350° C, 1 hour leads to a partial relaxation of internal stresses, as evidenced by the decrease of tensile and yield strength. The structure of the sample does not change. In the subsequent three cycles similar processing structure heterogeneity was preserved, but the area occupied by large grains decreased and amounted to ~20%.

From the data table. 2 shows that the deformation of the rolling KS titanium 75% also leads to higher values of tensile and yield strength and microhardness, however, these values are below the corresponding values for the UMP-titanium. In addition, the strain to fracture KS titanium will decrease about 5 times and becomes lower than appropriate for UMF titanium after similar treatment. Vacuum annealing of deformed by rolling at 75% KS-titanium at a temperature of 350°, 1 hour, as in the case of UMP-titanium, leads to a reduction in the values of microhardness and tensile and yield strength and increase in strain to failure. Subsequent processing cycles KS titanium scheme: cold rolling of 70-75% + annealing at a temperature of 350°, 1 hour, allow to obtain a titanium foil with a thickness of ~18 μm (When deformation by rolling KS-titanium more than 76% at the edges of the foil are observed cracks). Strength characteristics of the foil from the KS-titanium below the corresponding values for f is LGI, obtained from UMP-titanium. In addition, to foil obtained from the KS-titanium, there is an increase in the dispersion of the values of the tensile and yield strength for different samples with decreasing foil thickness. This increase in the dispersion of the values of ultimate strength and yield strength can be attributed to two factors: first, the heterogeneity of the structure of the foil obtained from the KS-titanium, secondly, with the presence of manufacturing defects (in our case, for example, a minor, within measurement accuracy, the heterogeneity of the foil thickness). It is known that the influence of the heterogeneity of the structure and manufacturing defects on the strength characteristics of the materials increases with decreasing thickness of the sample [7].

Thus, the proposed method of producing foil from UMP-titanium obtained by the method of pressing, significantly improves the mechanical properties of the foil, which allows its use in critical structures.

Literature

1. Alexandrov C.V., Anoshkin NF, Bochvar A.A. and other Semi-finished products from titanium alloys. M: Metallurgy. - 1979. - 512 S.

2. Nicholas L.A., Figlin SZ, Fighters .. and other Hot stamping and pressing of titanium alloys. M: metallurgy - 1975. - p.131-159 - 176-285 C.

3. Mazharova G. and other Machining of titanium alloys by pressure. M: Metallurgy. - 1977. - 228 S.

4. Zwicker U. Titanium and its alloys. Berlin - new-the Orc, 1974. TRANS. with it. - M.: metallurgy, 1979. - 512 S.

5. Valiev. R.Z., Alexandrov I.V. Nanostructured materials from severe plastic deformation. M: Logo. - 2000. - 272 S.

6. Kolobov YU, Valiev R.Z., G.P. Grabovetskaya, and other grain-boundary diffusion and properties of nanostructured materials. Novosibirsk: Nauka. - 2001. - 213 S.

7. Davidenkov NN. On the effect of sample sizes on the mechanical properties.// Factory laboratory. - 1960. No. 3.

The structure and grain size (d)
Table. 1

Structure and mechanical properties of the foil obtained from ultramalsoinclude titanium.
the cycle numberMaterial (state)The foil thickness, micronsTensile strength, MPaYield strength, MPaDeformation before fracture, %Microhardness, GPAThe structure and grain size (d)
0VT1-0, RKU pressing, (state 2)3800749-761725-7404,9-5,42,4C),35±0,12 µm
1 VT1-0, state 2 +warp 75%953992-1010884-9017,5-8,33,7d~0,15 µm
 W 1-0 condition 2 +warp 75%+ annealing to 350°S,1 h953913-938821-84513,9-15,03,2d~0,15 µm
2cycle 1 +deformation 70%286981-992873-8927,8-8,53,7d-0,1-0,15 µm
 cycle 1 +deformation 70%+ annealing to 350°S, 1 h)286884-908824-843to 11.9 and 12.43,2d-0,1-0,15 µm
3cycles 1 and 2 +deformation 86%40983-1080912-9566,8-7,5-d-0.1-0.15 m in the m
 cycles 1 and 2 +deformation 86%+ annealing to 350°S, 0.5 h)40901 through 916810-842of 7.4 to 8.1 d-0,1-0,15 µm
4cycles 1,2,3 +warp

75%
10955-995880-9204-5 d-0,1-0,15 µm
 cycles 1,2,3 +warp 75%+ annealing to 350°S, 1 h10905-920815-845the 7.5-8.5 d-0,1-0,15 µm
Table. 2

Structure and mechanical properties of the foil obtained from coarse-grained titanium.
The cycle numberMaterial (state)The foil thickness, micronsTensile strength, MPaYield strength, MPaDeformation before fracture, %Microhardness, GPA
0VT1-0 (state 1)380049338522,61,65d=5-10 µm
1VT1-0, state 1 +warp

75%
950799-806727-7494,5-4,92,9d=0,1-0,5 mkm% of the area occupied by the grain size of 5-10 microns
 VT1-0 state 2 +warp 75%+ annealing to 350°S,1 h950719-730681-6907,0-7,32,4d=0.1-0.5 micron. 30% of the area occupied by the grain size of 5-10 microns
2cycle 1 +deformation 70%285853-888770-7905,0-5,63,1d=0.1-0.5 micron. 30% of the area occupied by the grain size of 5-10 microns
 cycle 1 +deformation 70%+ annealing to 350°S, 1 h)285 823-848712-750of 7.9 to 8.32,7d=0.1-0.5 micron. 30% of the area occupied by the grain size of 5-10 microns
3cycles 1 and 2 +warp

75%
72817-867708-7403,2-3,5 d=0.1 to 0.3 μm. 20% of the area occupied by the grain size of 4-9 microns
 cycles 1 and 2 +warp 75%+ annealing to 350°S, 1 h)72720-737648-698of 6.0 to 7.1 d is 0.1 to 0.3 μm. 20% of the area occupied by the grain size of 4-9 microns
Continuation of table 2.
The cycle numberMaterial (state)The foil thickness, micronsTensile strength, MPaLimit fluid tee, IPADeformation before fracture, %Microhardness, GPAThe structure and grain size (d)
4cycles 1, 2 and 3 +warp 75% 18754-842660-728of 3.0-3.5 d=0.1 to 0.3 μm. 20% of the area occupied by the grain size of 4-9 microns
 cycles 1, 2 and 3 +warp 75%+ annealing to 350°S, 1 h18710-800665-7004-5 d=0.1 to 0.3 μm. 20% of the area occupied by the grain size of 4-9 microns

1. A method of obtaining a high-strength foil of titanium, representing repetitive cycles, each of which includes a multi-way reversing cold rolling and vacuum annealing, characterized in that the quality of the original piece used titanium with ultrafine-grained structure, and the rolling carry on with step 15-8% to the total deformation 70-86% per cycle, the number of cycles required for obtaining a given foil thickness, calculated by the formula

N=(lnhk-lnho)/ln(l-ε),

where N is the number of cycles;

ho- the original thickness of the blank;

hk- the final thickness of the foil;

ε - the average relative deformation (degree of compression) for one cycle.

2. The method according to claim 1, wherein the vacuum annealing is preferably Prov is car Ried out at a temperature of 350-360° C for 0.5-1 hours



 

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