Title:
ZINC-ALUMINUM ALLOY
United States Patent 3754904
Abstract:
A zinc-aluminum alloy comprises 18-24 % aluminum, 0.0005 - 0.05 % magnesium, 0.0025 - 0.25 % nickel, balance high-grade zinc. The form stability of the alloy can be improved by homogenizing it at a temperature above 275° to 380° C and aging it at a temperature above 80° C up to below 275° C for a time of 0.2 to 5 hours. The alloy has a high ductility, together with a high creep resistance.
US Patent References:
Zinc-base alloy
Peirce et al. - March 1928 - 1663215
Zinc base alloy
Werley - July 1935 - 2008529
Zinc-base alloy
Peirce et al. - March 1928 - 1663215
Zinc base alloy
Werley - July 1935 - 2008529
Application Number:
05/120718
Publication Date:
08/28/1973
Filing Date:
03/03/1971
View Patent Images:
Export Citation:
Assignee:
Stolberger-Zink AG Fur Bergbau Und Huttenbetrieb (Aachen, DT)
Primary Class:
Other Classes:
148/441
International Classes:
C22C18/04; C22C18/00; C22C17/00
Field of Search:
75/178A,178AM
Primary Examiner:
Rutledge, Dewayne L.
Assistant Examiner:
Weise E. L.
Claims:
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims
1. A zinc-aluminum alloy comprising
2. 0005 - 0.05 % magnesium;
3. 0025 - 0.25 % nickel; balance high-grade zinc.
4. The alloy of claim 1, in which aluminum is present in an amount of about 21 percent.
5. The alloy of claim 1, in which the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 percent.
6. The alloy of claim 1, wherein aluminum is present in an amount of 21 % and the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 %.
7. The alloy of claim 1, which comprises 21 % aluminum, 0.2 % nickel, 0.04 % magnesium, balance zinc.
8. The alloy of claim 1, wherein the amount of nickel present is substantially equal to at least five times the specific amount of magnesium present.
1. A zinc-aluminum alloy comprising
2. 0005 - 0.05 % magnesium;
3. 0025 - 0.25 % nickel; balance high-grade zinc.
4. The alloy of claim 1, in which aluminum is present in an amount of about 21 percent.
5. The alloy of claim 1, in which the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 percent.
6. The alloy of claim 1, wherein aluminum is present in an amount of 21 % and the magnesium content is 0.001 to 0.01 % and the nickel content is 0.005 to 0.05 %.
7. The alloy of claim 1, which comprises 21 % aluminum, 0.2 % nickel, 0.04 % magnesium, balance zinc.
8. The alloy of claim 1, wherein the amount of nickel present is substantially equal to at least five times the specific amount of magnesium present.
Description:
BACKGROUND OF THE INVENTION
The invention relates to a zinc-aluminum alloy.
Sheets and strips made of wrought zinc alloys, in addition to high strength, must normally have good shaping properties, both with regard to working by folding and bending and working by stamping and drawing.
Excellent wrought alloys with a high ductility are formed by binary zinc-aluminum alloys with about 1-63% aluminum and 37-99% zinc. The mixed crystalls of these alloys are caused to break down to a super-fine grain eutectic structure by suitable heat treatment. In this manner an alloy is formed of high ductility which possesses the property to undergo strong plastic deformation at extremely low mechanical stresses (DDRP [East German Patent] 4822; Sauerwald, F.: Arch. Metallkde., H. 5, 1949, p. 165; Mitbauer, H. and F. Sauerwald: Z. Metallkde., 43, 1952, p. 244; Schultze W. and F. Sauerwald: Z. Metallkde., 53, 1962, p. 660).
These alloys usually reach tensile strength values between 16 and 20 kp/mm 2 and elongation values of above 100%. Strips and sheets made from these alloys are therefore free of breaks when folded by 180° and are well suited for deep-drawing and for working in a vacuum shaping process. The creep resistance of these alloys, however, at an elongation of 1 percent per year is 0.4 kp/mm 2 which is entirely inadequate for practical purposes.
The creep resistance of the zinc-aluminum alloys can be improved by small additions of nickel which have a degree of solubility in solid aluminum and zinc.
(Wolf, W.: Zink ABC, Berlin 1950, p. 119; Burkhardt, A.: Technologie der Zinklegierungen, Berlin, 1940, pp. 22-24).
In other respects, however, the nickel causes the alloy to become more brittle. The excellent ductility of these alloys thus is almost completely lost and the elongation value at a tensile stress of 40 kp/mm 2 is reduced to below 10 percent.
According to a different proposal which is not prior art, there is added to an 18-24% aluminum-containing alloy nickel within the range of 0.1 to 1.5% and the alloy is subjected to homogenizing for an extended period of time at temperatures between 300° and 380°C. By a subsequent cooling to temperatures below 275° C a break down of the formed mixed crystals is obtained to form a fine grain eutectic structure. This results in a substantial improvement of the ductility.
The break down of the mixed crystals can be substantially retarded by adding magnesium to the zinc-aluminum alloy in order to suppress the inter-crystalline corrosion. The reason is that the solubility of the magnesium in solid zinc is reduced. The increase of strength is therefore accompanied again by a decrease of the ductility. The effect of the magnesium to make the alloy more brittle can be avoided only by keeping the magnesium content of the alloy at a level below 0.0005%. When a higher content of magnesium is used, it is necessary to cause the fine crystalline break down of the mixed crystals by an additional heat treatment at temperatures up to 275°. This type of heat treatment leads to the formation of a coarse grain which in turn results again in a decrease of the ductility (Mitbauer, H. and F. Sauerwald: Z. Metallkde., 43, 1952, p. 244-249).
This formation of a coarse grain structure can be obviated by adding to the nickel-containing zinc-aluminum alloy more than 0.05 and up to 0.25% magnesium and heating the alloy to a temperature in the range between 280 and 380° C, followed by subsequent cooling at a specific cooling rate (German published application 1 922 213). These steps retain the fine crystal structure which is necessary for a high ductility.
It has, however, been found that if for instance strips which are machine-rolled from this type of zinc-aluminum alloy, for instance to form channel-shaped structures or tubular structures, the rolled strip, when leaving the machine, will only partly retain the imposed deformation because of the strong tendency to a rebound caused by the high elasticity of the alloy.
It is therefore an object of the invention to provide for a zinc-aluminum alloy which avoids the described shortcomings.
SUMMARY OF THE INVENTION
The invention resides in a zinc-aluminum alloy which comprises 18 - 24 % aluminum, 0.0005 - 0.05 % magnesium, 0.0025 - 0.25 % nickel, balance high-grade zinc.
DETAILED DESCRIPTION OF THE INVENTION AND OF SPECIFIC EMBODIMENTS
Preferably, the aluminum content of the alloy of the invention is 21 %. The preferred magnesium content is 0.001 to 0.01 % magnesium. The nickel content is at least five time the specific amount of magnesium present.
The preferred aging temperature is between 120 and 200° C.
The described process features, in combination with the composition of the alloy, result in a Ni 2 Mg phase which is essentially the reason for the increased ductility, together with a simultaneous increase of the creep resistance.
The following examples will further describe and illustrate the invention, and furnish comparisons with prior-art alloys and alloys otherwise outside the scope of the invention.
The alloys described in the invention, in each case, were made by melting the components at a temperature of 450°C and casting the alloy to ingots of the thickness of 4 cm. After a subsequent homogenizing treatment, at a temperature of 350°C, each ingot was hot rolled at a temperature of 300°C in several passes to a final sheet thickness of 1 mm.
EXAMPLE 1
A prior-art alloy, consisting of
21% aluminum
79% zinc
and formed into a sheet as described before had the following mechanical properties:
tensile strength 20 kp/mm 2 elongation 150% creep resistance 0.4 kp/mm 2 EXAMPLE 2 A sheet was formed from a prior-art alloy comprising
21 % aluminum
0.2 % nickel
balance high-grade zinc
The sheet had the following properties
tensile strength 21 kp/mm 2 elongation 130% creep resistance 1.2 kp/mm 2 EXAMPLE 3 A sheet was formed of a prior-art alloy comprising
21% aluminum
0.04% magnesium
balance high-grade zinc
The sheet had the following properties:
tensile strength 30 kp/mm 2 elongation 10% creep resistance 6.5 kp/mm 2
After heat-aging for 2 hours, at 180°C, the mechanical properties were improved as follows:
tensile strength 33 kp/mm 2 elongation 15% creep resistance 7.0 kp/mm 2 EXAMPLE 4 In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.2 % nickel
0.04 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 30 kp/mm 2
elongation 15 %
creep resistance 6.5 kp/mm 2
After heat-aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 33 kp/mm 2
elongation 80 %
creep resistance 8.0 kp/mm 2 .
EXAMPLE 5
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
18 % aluminum
0.1 % nickel
0.00l % magnesium
balance high-grade zinc
The following values were found:
tensile strength 29 kp/mm 2
elongation 15 %
creep resistance 6 kp/mm 2
After heat-aging at a temperature of 180° C for two hours, the mechanical properties were improved to the following figures:
tensile strength 32 kp/mm 2
elongation 110 %
creep resistance 7.5 kp/mm 2 .
EXAMPLE 6
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
24 % aluminum
0.25 % nickel
0.01 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 30 kp/mm 2
elongation 15 %
creep resistance 6.5 kp/mm 2
After heat-aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 31 kp/mm 2
elongation 90 %
creep resistance 7.5 kp/mm 2 .
EXAMPLE 7
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.025 % nickel
0.005 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 27 kp/mm 2
elongation 15 %
creep resistance 5 kp/mm 2
After heat aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 29 kp/mm 2
elongation 95 %
creep resistance 7.0 kp/mm 2 .
EXAMPLE 8
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.0025 % nickel
0.0005 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 26 kp/mm 2
elongation 15 %
creep resistance 4,5 kp/mm 2
After heat aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 28 kp/mm 2
elongation 75 %
creep resistance 5.5 kp/mm 2
Comparing the tensile strength, the elongation and the creep resistance, particularly as between the sheets of Example 3 and Examples 4, 5, 6, 7 and 8, it will be noted that the elongation of the zinc-aluminum alloy of the invention is improved by more than five times by means of the heat treatment of the invention, together with a simultaneous increase of the creep resistance. The ductility thus obtained, although it is not quite as good as that of the zinc-aluminum alloys of Examples 1 and 2, is entirely adequate for meeting the shaping properties of industrial practice.
Without further analysis, the foregoing will so fully reveal the gist of the invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
The invention relates to a zinc-aluminum alloy.
Sheets and strips made of wrought zinc alloys, in addition to high strength, must normally have good shaping properties, both with regard to working by folding and bending and working by stamping and drawing.
Excellent wrought alloys with a high ductility are formed by binary zinc-aluminum alloys with about 1-63% aluminum and 37-99% zinc. The mixed crystalls of these alloys are caused to break down to a super-fine grain eutectic structure by suitable heat treatment. In this manner an alloy is formed of high ductility which possesses the property to undergo strong plastic deformation at extremely low mechanical stresses (DDRP [East German Patent] 4822; Sauerwald, F.: Arch. Metallkde., H. 5, 1949, p. 165; Mitbauer, H. and F. Sauerwald: Z. Metallkde., 43, 1952, p. 244; Schultze W. and F. Sauerwald: Z. Metallkde., 53, 1962, p. 660).
These alloys usually reach tensile strength values between 16 and 20 kp/mm 2 and elongation values of above 100%. Strips and sheets made from these alloys are therefore free of breaks when folded by 180° and are well suited for deep-drawing and for working in a vacuum shaping process. The creep resistance of these alloys, however, at an elongation of 1 percent per year is 0.4 kp/mm 2 which is entirely inadequate for practical purposes.
The creep resistance of the zinc-aluminum alloys can be improved by small additions of nickel which have a degree of solubility in solid aluminum and zinc.
(Wolf, W.: Zink ABC, Berlin 1950, p. 119; Burkhardt, A.: Technologie der Zinklegierungen, Berlin, 1940, pp. 22-24).
In other respects, however, the nickel causes the alloy to become more brittle. The excellent ductility of these alloys thus is almost completely lost and the elongation value at a tensile stress of 40 kp/mm 2 is reduced to below 10 percent.
According to a different proposal which is not prior art, there is added to an 18-24% aluminum-containing alloy nickel within the range of 0.1 to 1.5% and the alloy is subjected to homogenizing for an extended period of time at temperatures between 300° and 380°C. By a subsequent cooling to temperatures below 275° C a break down of the formed mixed crystals is obtained to form a fine grain eutectic structure. This results in a substantial improvement of the ductility.
The break down of the mixed crystals can be substantially retarded by adding magnesium to the zinc-aluminum alloy in order to suppress the inter-crystalline corrosion. The reason is that the solubility of the magnesium in solid zinc is reduced. The increase of strength is therefore accompanied again by a decrease of the ductility. The effect of the magnesium to make the alloy more brittle can be avoided only by keeping the magnesium content of the alloy at a level below 0.0005%. When a higher content of magnesium is used, it is necessary to cause the fine crystalline break down of the mixed crystals by an additional heat treatment at temperatures up to 275°. This type of heat treatment leads to the formation of a coarse grain which in turn results again in a decrease of the ductility (Mitbauer, H. and F. Sauerwald: Z. Metallkde., 43, 1952, p. 244-249).
This formation of a coarse grain structure can be obviated by adding to the nickel-containing zinc-aluminum alloy more than 0.05 and up to 0.25% magnesium and heating the alloy to a temperature in the range between 280 and 380° C, followed by subsequent cooling at a specific cooling rate (German published application 1 922 213). These steps retain the fine crystal structure which is necessary for a high ductility.
It has, however, been found that if for instance strips which are machine-rolled from this type of zinc-aluminum alloy, for instance to form channel-shaped structures or tubular structures, the rolled strip, when leaving the machine, will only partly retain the imposed deformation because of the strong tendency to a rebound caused by the high elasticity of the alloy.
It is therefore an object of the invention to provide for a zinc-aluminum alloy which avoids the described shortcomings.
SUMMARY OF THE INVENTION
The invention resides in a zinc-aluminum alloy which comprises 18 - 24 % aluminum, 0.0005 - 0.05 % magnesium, 0.0025 - 0.25 % nickel, balance high-grade zinc.
DETAILED DESCRIPTION OF THE INVENTION AND OF SPECIFIC EMBODIMENTS
Preferably, the aluminum content of the alloy of the invention is 21 %. The preferred magnesium content is 0.001 to 0.01 % magnesium. The nickel content is at least five time the specific amount of magnesium present.
The preferred aging temperature is between 120 and 200° C.
The described process features, in combination with the composition of the alloy, result in a Ni 2 Mg phase which is essentially the reason for the increased ductility, together with a simultaneous increase of the creep resistance.
The following examples will further describe and illustrate the invention, and furnish comparisons with prior-art alloys and alloys otherwise outside the scope of the invention.
The alloys described in the invention, in each case, were made by melting the components at a temperature of 450°C and casting the alloy to ingots of the thickness of 4 cm. After a subsequent homogenizing treatment, at a temperature of 350°C, each ingot was hot rolled at a temperature of 300°C in several passes to a final sheet thickness of 1 mm.
EXAMPLE 1
A prior-art alloy, consisting of
21% aluminum
79% zinc
and formed into a sheet as described before had the following mechanical properties:
tensile strength 20 kp/mm 2 elongation 150% creep resistance 0.4 kp/mm 2 EXAMPLE 2 A sheet was formed from a prior-art alloy comprising
21 % aluminum
0.2 % nickel
balance high-grade zinc
The sheet had the following properties
tensile strength 21 kp/mm 2 elongation 130% creep resistance 1.2 kp/mm 2 EXAMPLE 3 A sheet was formed of a prior-art alloy comprising
21% aluminum
0.04% magnesium
balance high-grade zinc
The sheet had the following properties:
tensile strength 30 kp/mm 2 elongation 10% creep resistance 6.5 kp/mm 2
After heat-aging for 2 hours, at 180°C, the mechanical properties were improved as follows:
tensile strength 33 kp/mm 2 elongation 15% creep resistance 7.0 kp/mm 2 EXAMPLE 4 In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.2 % nickel
0.04 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 30 kp/mm 2
elongation 15 %
creep resistance 6.5 kp/mm 2
After heat-aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 33 kp/mm 2
elongation 80 %
creep resistance 8.0 kp/mm 2 .
EXAMPLE 5
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
18 % aluminum
0.1 % nickel
0.00l % magnesium
balance high-grade zinc
The following values were found:
tensile strength 29 kp/mm 2
elongation 15 %
creep resistance 6 kp/mm 2
After heat-aging at a temperature of 180° C for two hours, the mechanical properties were improved to the following figures:
tensile strength 32 kp/mm 2
elongation 110 %
creep resistance 7.5 kp/mm 2 .
EXAMPLE 6
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
24 % aluminum
0.25 % nickel
0.01 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 30 kp/mm 2
elongation 15 %
creep resistance 6.5 kp/mm 2
After heat-aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 31 kp/mm 2
elongation 90 %
creep resistance 7.5 kp/mm 2 .
EXAMPLE 7
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.025 % nickel
0.005 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 27 kp/mm 2
elongation 15 %
creep resistance 5 kp/mm 2
After heat aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 29 kp/mm 2
elongation 95 %
creep resistance 7.0 kp/mm 2 .
EXAMPLE 8
In this example a sheet was formed as described from an alloy according to the present invention which comprised:
21 % aluminum
0.0025 % nickel
0.0005 % magnesium
balance high-grade zinc
The following values were found:
tensile strength 26 kp/mm 2
elongation 15 %
creep resistance 4,5 kp/mm 2
After heat aging at a temperature of 180° C for 2 hours, the mechanical properties were improved to the following figures:
tensile strength 28 kp/mm 2
elongation 75 %
creep resistance 5.5 kp/mm 2
Comparing the tensile strength, the elongation and the creep resistance, particularly as between the sheets of Example 3 and Examples 4, 5, 6, 7 and 8, it will be noted that the elongation of the zinc-aluminum alloy of the invention is improved by more than five times by means of the heat treatment of the invention, together with a simultaneous increase of the creep resistance. The ductility thus obtained, although it is not quite as good as that of the zinc-aluminum alloys of Examples 1 and 2, is entirely adequate for meeting the shaping properties of industrial practice.
Without further analysis, the foregoing will so fully reveal the gist of the invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.