Method for heat treating an aluminum alloy and method for producing a component

Abstract

A method for heat treating an aluminum alloy, comprising the steps: - Providing an aluminum alloy, wherein the aluminum alloy comprises, in addition to aluminum: ◯ a magnesium content of more than 0.5 wt.% ◯ a copper content of less than or equal to 1.0 wt.% ◯ a manganese content of 0.4 wt% to 0.7 wt% ◯ a strontium content of 0.01 wt% to 0.05 wt%, - Solution annealing of the aluminium alloy at a temperature of 460°C to 490°C for a period of 0.5 h to 6 h, - then quenching the aluminum alloy with water and then - Artificial aging of the aluminium alloy for a period of 6 hours at a temperature of 180°C and then for a period of 4 hours at a temperature of 220°C.

Description

[0001] The invention relates to a method for heat treating an aluminum alloy and a method for producing a component.

[0002] The copper-rich (Cu > 1.5 wt%) and magnesium-poor (Mg < 0.3 wt%) aluminum alloys that can be cast by die casting show high static mechanical strength but only low elongation.

[0003] Well-known aluminum die-casting alloys are available, for example, under the name Silafont-36, which is a die-casting alloy of the type AlSi9MgMn with strontium, containing 9.5 wt.% to 11.5 wt.% Si, up to 0.15 wt.% Fe, up to 0.03 wt.% Cu, 0.5 wt.% to 0.8 wt.% Mn, 0.1 wt.% to 0.5 wt.% Mg, up to 0.08 wt.% Zn, 0.04 wt.% to 0.15 wt.% Ti, 0.010 wt.% to 0.020 wt.% Sr and up to 0.001 wt.% P, or the Al alloy under the name Aural-2, containing 9.5 wt.% to 11.5 wt.% Si, 0.3 wt.% to 0.6 wt.% Mn, 0.1 wt% to 0.4 wt% Mg, up to 0.25 wt% Fe, up to 0.1 wt% Ti and 0.010 wt% to 0.018 wt% Sr.

[0004] DE 10 2005 061 668 A1 discloses an aluminum alloy for die casting comprising 0.9 to 12.0 wt% Si, 0.20 to 0.80 wt% Mg and 0.7 to 1.1 wt% Mn + Fe, wherein the Mn / Fe ratio is 1.5 or more and the Cu content as an impurity is adjusted to 0.5 wt% or less and the remainder is formed by aluminum and unavoidable impurities.

[0005] DE 10 2008 046 803 A1 discloses an aluminum alloy for a cast component of a motor vehicle. The aluminum alloy is a cast aluminum alloy and contains 6.5 to 11.7 wt.% silicon, 0.4 to 1.0 wt.% manganese, 0.05 to 0.5% magnesium, 0.01 to 0.5 wt.% copper, 0.05 to 0.31 wt.% iron, and the remainder aluminum with a maximum of 0.05 wt.% individually and a maximum of 0.2 wt.% in total of manufacturing-related impurities. Furthermore, US 2009 / 0 038 720 A1 discloses a method for heat treating a cast component.

[0006] JP H01 - 108 339 A discloses a piston which is formed from an aluminum alloy.

[0007] Furthermore, WO 2011 / 030500 A1 discloses a component made of an aluminum alloy which contains 7.0 to 11.5 mass percent silicon, 0.9 to 4.0 mass percent magnesium, 0.1 to 0.65 mass percent iron, 0.1 to 0.8 mass percent manganese and the remainder aluminum and unavoidable impurities.

[0008] DE 195 24 564 A1 discloses an aluminum casting alloy, in particular for casting cylinder heads.

[0009] CN 1 02 206 778 A discloses an aluminum casting alloy for die casting of automotive parts.

[0010] EP 1 997 924 A1 discloses a cold-hardening aluminum casting alloy for the production of thermally and mechanically stressed castings.

[0011] DE 102011 112 005 A1 discloses an aluminum-silicon alloy suitable for sand, die and pressure casting.

[0012] Based on this, the present invention is based on the problem of providing a heat treatment for an aluminum alloy which is particularly suitable for die casting, as well as a corresponding manufacturing method for a component which enables high mechanical strength and, at the same time, high ductility of the alloy.

[0013] The invention is based on the surprising finding that by adjusting the amounts of copper <= 1 wt.% and magnesium > 0.5 wt.% and in particular by a heat treatment adapted thereto, the alloy exhibits high static mechanical strengths with high ductility, whereby design advantages and in particular wall thickness reductions are possible, which result in a corresponding lightweight construction potential of the alloy according to the invention and a concomitant reduction in CO2 and consumption.

[0014] The aluminum alloy contains 0.4 wt% to 0.7 wt% manganese and 0.01 wt% to 0.05 wt% strontium.

[0015] It is intended that the aluminum alloy preferably contains greater than 0.5 wt.% to 1.0 wt.% magnesium, and preferably 0.2 wt.% to 1.0 wt.% copper.

[0016] The alloy does not contain any other components (elements) (except for possibly negligible impurities).

[0017] In order to increase the strength of the aluminum alloy, the invention provides a special process, tailored to the alloy, for heat-treating the alloy or a component made of the alloy.

[0018] Such strength increases in an alloy are usually based on the obstruction of dislocation sliding, which is a major mechanism of plastic deformation. Similarly, the strength increase can be based on the (homogeneous) incorporation of obstacles into the sliding path of dislocations.

[0019] The initial state of a corresponding strength-enhancing heat treatment is usually a solid (stable) (cast) state of the alloy.

[0020] Such a heat treatment can now comprise the steps of solution annealing, quenching and ageing of the aluminum alloy according to the invention or a component consisting thereof.

[0021] During solution annealing, the alloying elements dissolve in the solid solution, and a supersaturated solid solution forms during the subsequent quenching (metastable state). During age-hardening (hot aging), the aforementioned strength-enhancing precipitates finally form from the supersaturated solid solution.

[0022] According to the method according to the invention for heat treating an aluminum alloy according to the invention, the following steps are provided: providing an above-mentioned aluminum alloy, in particular in a solid (stable) (as cast) state, solution annealing said aluminum alloy at a temperature of 460°C to 490°C for a period of 0.5 hours to 6 hours, then quenching the aluminum alloy with water, in particular to a temperature <= 180°C and then artificially aging said aluminum alloy for a period of 6 hours at a temperature of 180°C and subsequently for a period of 4 hours at a temperature of 220°C.

[0023] In this respect, the aluminum alloy primarily shows the strength-enhancing, so-called “Q-phase”, Al5Cu2Mg8Si6, which is less brittle than Mg2Si (at Cu < 0.25 wt.%) or Al2Cu (at Cu > 1 wt.%).

[0024] This Q phase dissolves even at comparatively low solution annealing temperatures (<= 490°C). Solution annealing in the range of 460°C to 490°C for a period of 0.5 to 6 hours, as well as the aforementioned water quenching and artificial ageing, results in an alloy yield strength of < 240 MPa and an elongation of > 2%.

[0025] Quenching can be carried out by immersion cooling of the alloy, in which the alloy or a corresponding component is immersed in water, or by splash water cooling, in which the alloy or a corresponding component is exposed to water.

[0026] A component is in particular a motor vehicle component, in particular a cylinder crankcase of an engine of a motor vehicle.

[0027] Furthermore, the invention proposes a (die-casting) method for producing a component according to the invention, in particular in the form of a motor vehicle part (see above), comprising the steps of: providing an aluminum alloy according to the invention, die-casting the aluminum alloy in a flowable state in a tool for forming the component, removing the (solid) component from the tool, solution-annealing the component at a temperature of 460°C to 490°C for a period of 0.5 h to 6 h, then quenching the component with water (see above) and then artificially aging the component for a period of 6 hours at a temperature of 180°C and subsequently for a period of 4 hours at a temperature of 220°C.

Claims

[1] A method for heat treating an aluminum alloy, comprising the steps of: - Providing an aluminum alloy, wherein the aluminum alloy comprises, in addition to aluminum: ◯ a magnesium content of more than 0.5 wt.% ◯ a copper content of less than or equal to 1.0 wt.% ◯ a manganese content of 0.4 wt% to 0.7 wt% ◯ a strontium content of 0.01 wt% to 0.05 wt%, - Solution annealing of the aluminium alloy at a temperature of 460°C to 490°C for a period of 0.5 h to 6 h, - then quenching the aluminum alloy with water and then - Artificial aging of the aluminium alloy for a period of 6 hours at a temperature of 180°C and then for a period of 4 hours at a temperature of 220°C. [2] Method according to claim 1, characterized bythat quenching is carried out by immersion cooling or by splash water cooling. [3] Method for producing a component, comprising the steps: - Providing an aluminum alloy, wherein the aluminum alloy comprises, in addition to aluminum: ◯ a magnesium content of more than 0.5 wt.% ◯ a copper content of less than or equal to 1.0 wt.% ◯ a manganese content of 0.4 wt% to 0.7 wt% o a strontium content of 0.01 wt% to 0.05 wt%, - Die-casting the aluminum alloy in a flowable state in a tool to form the component, - Removing the component from the tool, - Solution annealing of the component at a temperature of 460°C to 490°C for a period of 0.5 h to 6 h, - then quench the component with water and then - Artificial aging of the component over a period of 6 hours at a temperature of 180°C and then over a period of 4 hours at a temperature of 220°C.