PROCESS FOR OBTAINING A LOW SILICON ALUMINIUM ALLOY PART

Abstract

The part made of low-silicon aluminum alloy contains magnesium, copper, manganese, titanium, and strontium. Said part is obtained by a method that consists in: casting said alloy in a mold so as to obtain the part; after the casting, demolding the part constituting a preform that is still hot; cooling said preform and then subjecting it to an operation suitable for reheating it to a temperature lying in the range 470° C. to 550° C.; positioning said part between two shells of a die that defines a cavity of dimensions substantially equal to but less than the dimensions of the cavity of the mold; and strongly pressing the two shells together to exert on the part disposed between said shells a combined pressing and surface kneading effect.

Claims

1. A method of obtaining a part made of low-silicon aluminum alloy, containing the alloy comprising: silicon at a content lying in the range of 0.5% to 3%; magnesium at a content lying in the range of 0.65% to 1%; copper at a content lying in the range of 0.20% to 0.40%; manganese at a content lying in the range of 0.15% to 0.25%; titanium at a content lying in the range of 0.10% to 0.20%; and strontium at a content lying in the range of 0 ppm to 120 ppm; said method including: casting said alloy in a mold so as to obtain the part; after the casting, demolding the part constituting a preform that is still hot; cooling said preform and then subjecting said preform to an operation adapted for reheating saisd preform to a temperature lying in the range of 470° C. to 550° C.; positioning said part between two shells of a die that defines a cavity of dimensions substantially equal to but less than the dimensions of the cavity of the mold; and strongly pressing the two shells together to exert on the part disposed between said shells a combined effect of pressing and surface kneading.

2. An automobile part comprising the Use of a part obtained by the method according to claim 1.

3. An aviation part comprising the part obtained by the method according to claim 1.

Description

[0035] Reference is made to the figures of the accompanying drawings that show the metallographs of a part in order to show the importance of the manganese content and of the copper content. FIG. 1 shows a casting microstructure, without any manganese, and “needle” precipitates of the β type, while FIG. 2 shows the monostructure with manganese, and “Chinese script” precipitates of the a type.

[0036] FIGS. 3, 4, and 5 show the elimination of the Al.sub.2Cu copper precipitates.

[0037] In FIGS. 3 and 4, the copper content is greater than 0 40%, which leads to the presence of Al.sub.2Cu precipitates. FIG. 4 shows an example in which it is possible to observe the AlFeMnSi and Mg.sub.2Si precipitations surrounded by Al.sub.2Cu precipitates.

[0038] FIG. 5 shows a copper content lying in the range 0.20% to 0.40%, in accordance with the invention, showing absence of Al.sub.2Cu precipitates.