Superplastic aluminum alloy strips and process for producing the

Details Superplastic aluminum alloy strips and process for producing the Superplastic aluminum alloy strips and process for producing the

1984-03-16

1986-10-28

Rutledge, L Dewayne

Metal treatment

Compositions

Heat treating

148 115A, 148440, 420902, C22F 1047

Patent

active

046197125

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to superplastic aluminum alloy strips and a process for producing the same. Particularly, the present invention relates to a process for easily producing superplastic aluminum alloy strips on an industrial scale.
2. Background Art
Metals or alloys which can be elongated to an abnormal extent of hundreds to thousand percents without generating local deformation (necking) when a mechanical force is externally applied thereon have been known as superplastic metals or superplastic alloys. In general, these superplastic metals and alloys are broadly divided into the two types of extra fine crystal grain-type and transformation-type according to the mechanism of showing their superplasticity. The superplastic alloys based on aluminum are classified to the extra fine crystal grain-type superplastic alloys and according to their fine crystal structure made with crystal grains of from 0.5 micrometer or less to 10 micrometers in diameter, the material of superplastic aluminum alloy is easily subjected to the plastic deformation by the smooth grain boundary migration or sliding.
It is an object of the present invention to provide a strip of superplastic aluminum alloy having excellent superplasticity.
Another object of the present invention is to provide a process for producing superplastic aluminum alloy strips showing excellent superplasticity by combining the composition of the alloy and the conditions in casting and rolling.


Disclosure of Invention

The subject matters of the present invention consist in superplastic aluminum alloy strips comprising 1.5 to 9.0% (by weight, hereinafter % relating to an alloy component always means % by weight) of magnesium, 0.5 to 5.0% of silicon, 0.05 to 1.2% of manganese, 0.05 to 0.3% of chromium and the balance consisting essentially of aluminum, and also a process for producing superplastic aluminum alloy strips comprising continuously casting and rolling a molten aluminum alloy containing 1.5 to 9.0% of magnesium, 0.5 to 5.0% of silicon, 0.05 to 1.2% of manganese and 0.05 to 0.3% of chromium, thereby obtaining a cast strip of 3 to 20 mm in thickness, homogenizing the cast strip at a temperature of 430.degree. to 550.degree. C., and subjecting the homogenized strip to cold rolling until the reduction ratio reaches up to a value of not less than 60%. The aluminum alloy strips of the present invention shows excellent super-plasticity at a temperature of higher than 400.degree. C., particularly in the range of 450.degree. to 600.degree. C.


BRIEF DISCRIPTION OF THE DRAWING

FIGS. 1 and 2 respectively show a typical cross-sectional view of a metal mold for the bulge test used in Examples of the present invention. FIG. 1 shows the state in which a test sheet is set to the metal mold, and FIG. 2 shows the state in which the test sheet has been expanded downward by compressed air.


BEST MODE OF CARRYING OUT THE INVENTION

The present invention will be explained more in detail as follows.
The superplastic aluminum alloy strip according to the present invention contains 1.5 to 9.0% of magnesium, 0.5 to 5.0% of silicon, 0.05 to 1.2% of manganese and 0.05 to 0.3% of chromium, and the balance consisting essentially of aluminum.
In the dynamic recrystallization, namely, the plastic deformation of the superplastic aluminum alloy strip, magnesium and silicon have a function of regenerating always the original structure before the deformation by recrystallization simultaneous with the deformation. In the case where the amount of magnesium and silicon is too small, their effect is not fully exhibited, and on the other hand, in the case where their amount is too large, the workability of the alloy strip, particularly the rollability of the alloy strip is deteriorated. The preferable each content of magnesium and silicon is 2.0 to 8.0% and 1.0 to 4.0%. Magnesium and silicon form together with a compound (Mg.sub.2 Si) and this compound, as being fine particles, contributes to the exhibition of superplasticity. Manganese and chromiu

REFERENCES:
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