Al-Mg-Si alloy having a high ductility and method of its manufacture

Abstract

An AlMgSi-alloy suitable for manufacturing components having a high ductility, characterized in that the alloy comprising, in wt. %: <table-cwu id="TABLE-US-00001"> <number>1< / number> <tgroup align="left" colsep="0" rowsep="0" cols="4"> <colspec colname="OFFSET" colwidth="56PT" align="left" / > <colspec colname="1" colwidth="63PT" align="left" / > <colspec colname="2" colwidth="28PT" align="right" / > <colspec colname="3" colwidth="70PT" align="left" / > <row> <entry>< / entry> <entry>< / entry> < / row> <row> <entry>< / entry> <entry namest="OFFSET" nameend="3" align="center" rowsep="1">< / entry> < / row> <row> <entry>< / entry> <entry>Mg< / entry> <entry>0.3 to< / entry> <entry>1.0< / entry> < / row> <row> <entry>< / entry> <entry>Si< / entry> <entry>0.3 to< / entry> <entry>1.2< / entry> < / row> <row> <entry>< / entry> <entry>Fe< / entry> <entry>max.< / entry> <entry>0.35< / entry> < / row> <row> <entry>< / entry> <entry>Mn< / entry> <entry>>0.15 to< / entry> <entry>0.4< / entry> < / row> <row> <entry>< / entry> <entry>V< / entry> <entry>0.05 to< / entry> <entry>0.20< / entry> < / row> <row> <entry>< / entry> <entry>Cu< / entry> <entry>max.< / entry> <entry>0.3< / entry> < / row> <row> <entry>< / entry> <entry>Cr< / entry> <entry>max.< / entry> <entry>0.2< / entry> < / row> <row> <entry>< / entry> <entry>Zn< / entry> <entry>max.< / entry> <entry>0.2< / entry> < / row> <row> <entry>< / entry> <entry>Ti< / entry> <entry>max.< / entry> <entry>0.1< / entry> < / row> <row> <entry>< / entry> <entry namest="OFFSET" nameend="3" align="center" rowsep="1">< / entry> < / row> < / tgroup> < / table-cwu> impurities max. 0.05% each, total max. 0.15%, balance aluminium

Description

[0001] The invention relates to an AlMgSi-alloy suitable for manufacturing components having a high ductility and to a method for the manufacture of such a new aluminium alloy. Hot-worked products, in particular obtained by means of extrusion, of the alloy of this invention can be used for example in railway vehicles, or in welded structures, or can be further formed by means of hydroforming.DESCRIPTION OF THE RELATED ART[0002] Al--Mg--Si type aluminium alloys such as Aluminium Association 6xxx series aluminium alloys are widely used and favoured for their moderately high yield and tensile strength, low quench sensitivity, good corrosion resistance and favourable forming characteristics. AA6xxx series alloys are increasingly attractive to industries such as transportation because of these well-known properties. Further AA6xxx series alloys exhibit in general satisfactory welding characteristics, by which this type of alloy is also widely used for applications resulting in the constr...

AI Technical Summary

Benefits of technology

[0020] By the invention we can provide alloy plate or extrusions having good strength, improved ductility, good resistance to corrosion and, in particular in the case of extruded products, exhibits a uniform surface, absence of die pick-up, good longitudinal weld seams, and the possibility to extrude complicated shaped sections which can be both thin and / or thick walled and can be processed at economic extrusion rates. In particular the increased manganese content in the aluminium alloy in accordance with the invention attributes to an improved ductility and a better welding behaviour. Further the aluminium alloy has improved properties after welding and is less sensitive for hot-cracking during welding and after extrusion and heat-treatments has a fine-grained recrystallized microstructure. And further the aluminium alloy has a lower quench-sensitivity than aluminium alloys from the AA6005 A-series type.

[0027] Chromium improves the corrosion resistance of the alloy. However, chromium limits the solubility of manganese and further reduces the extrudibility of the aluminium alloy. Therefor, to avoid formation of coarse primaries and to improve extrusion capability, the chromium content must not be more than 0.2 wt. %, preferably not more than 0.1 wt. %, and more preferably not more than 0.06 wt. %.

[0036] In this way, it is achieved that the product acquires excellent properties against a reasonable cost level for the applications which the inventors have in mind.

[0038] After casting, the aluminium alloy is homogenised. The aim of the homogenising treatment is amongst other things, to homogenise the microstructure, to dissolve the magnesium and silicon, to level off possible residual stresses resulting from the casting process, and to spheroidize sharp or needle shaped intermetallic compounds formed during solidification of the aluminium alloy. A homogenisation for of 8 to30 hours in a temperature in the range of 530.degree. C. to just below the melting temperature of the aluminium alloy is sufficient. A longer homogenisation time is not disadvantageous, but is not required and only serves to raise the costs of production. Preferably, the alloy is homogenised for 8 to 20 hours in a temperature range of 580.degree. C. to just below the melting temperature of the aluminium alloy. More preferably, the alloy is homogenised for 8 to 16 hours in a temperature range of 590 to 605.degree. C. It has been found that such a high homogenisation temperature is advanteaous for hot-working the alloy by means of extrusion into complex shaped sections which can be both thin walled or thick walled. In this manner an acceptable extrusion rate can be maintained despite of the relatively high Mn-content. Further due to the relatively high homogenisation treatment the final product has a fine-grained fully recrystallized microstructure.

Problems solved by technology

However, chromium limits the solubility of manganese and further reduces the extrudibility of the aluminium alloy.