HK1245355B - Cast alloy - Google Patents

Description

The Commission has also adopted a proposal for a directive on the protection of workers from risks related to exposure to ionising radiation.

The invention relates to a cast alloy based on aluminium, magnesium and iron, particularly for use in vehicle structural components.

The Technical Standards

Alloy alloys are commonly known and are considered to be part of the 8000 alloy group of aluminium alloys.Also, numerous publications talk about intermetallic AlFe materials, also called iron-aluminides, which have a high iron content and other alloying elements.These materials are not castings.They are used in powder metallurgy (e.g. for surface coating), in sintering processes, in 3D printing processes or similar.

The patent literature in the field of aluminotherapy refers to the use of this alloy for sheet metal, extrusion products, coating techniques and the application of this alloy in powder products. Representative of a large number of patent publications in the field of knitted alloy products, US8206519 B2, US7462410 B2, US20060213590 A1 and DE60320387 T2 are mentioned here. Another area of application for aluminotherapy is magnetic components used for information storage.

In the field of cast alloys, in particular die pressure cast alloys, the main applications are the Al-Si and Al-Mg-Si alloy systems. The applicant itself has been active for many years in the development of die cast alloys for the automotive industry. A corresponding number of patents already granted are represented by the following: EP14431 22B1 and EP1612286B1.

The lightweight construction of the automotive industry requires simple, robust manufacturing processes. In the case of structural components, this means, among other things, the elimination of heat treatments. This not only saves a manufacturing process step, but also the directional work that is usually required due to the inevitable delay. It also requires the ability to perform a surface treatment process at temperatures of 190 °C and above without affecting the material properties of the alloy. Other requirements are an alloy with easier machinability, such as easy adhesibility, a low resource saving during casting or a simple melting of the backing material.

It is also appropriate to mention the applicant's own WO 96/15281, which reveals an aluminium alloy containing 3.0 to 6.0% by weight of magnesium, 1.4 to 3.5% by weight of silicon, 0.5 to 2.0% by weight of manganese, up to 0.15% by weight of iron, up to 0.2% by weight of titanium, and aluminium residues and other impurities of up to 0.02 by weight each, totalling up to 0.2% by weight.

The following shall be considered as a single product:

The present invention is intended to provide a cast alloy based on aluminium-magnesium irons which satisfies at least one of the requirements mentioned above.

According to the invention, this task is solved by the following casting: Other

Eisen	0,8 - 3.0
Magnesium	2,0 bis 7,0 Gew. %
Mangan	0 - 2,5 Gew. %
Beryllium	0 - 500 ppm
Titan	0 - 0,5 Gew. %
Silizium	0-0,4%
Strontium	0 - 0,8 Gew. %
Phosphor	0 - 500 ppm
Kupfer	0 - 4 Gew. %
Zink	0 - 10 Gew. %

0- 0,5% by weight of an element or group of elements selected from the group consisting of chromium, nickel, molybdenum, zircon, vanadium, hafnium, calcium, gallium and boron, and the remainder of aluminium and unavoidable impurities.

Preferred embodiments of the invention are set out in the dependent claims.

In one embodiment, the iron content of the cast alloy is between 1.0 and 2.4% by weight of iron.

In another embodiment, the iron content of the cast alloy is between 1.4% and 2.2% by weight of iron.

In another embodiment, the magnesium content of the cast alloy is between 3.0 and 5.0% by weight of magnesium.

In one embodiment, the manganese content is between 0 and 0,6% by weight.

In one embodiment, the beryllium content is between 0 and 100 ppm.

In one embodiment the strontium content is between 0 and 0.03 weight % .

In one embodiment, the zinc content is between 0 and 0,5 wt. %.

In one embodiment, the phosphorus content is between 0 and 50 ppm.

In one embodiment the copper content is between 0 and 0.2% by weight.

In one embodiment, the titanium content is between 0 and 0,1 wt. %.

The alloy of the invention is used preferably for die casting, in particular for die casting of structural components for the automotive industry.

Where casting is referred to below, this includes an alloy, in particular for die casting, shell casting or sand casting.

The alloy is based on an AlFe alloy system, which has not been used in automotive castings. This system is also ductile and can be solidified by magnesium without creating trinitarian phases AlMgFe.

The alloy of the invention, with the exception of the basic elements aluminium, iron and magnesium, can be used without additional elements to achieve a tensile strength of 70 MPa at a 20% fracture stress and a bend angle of 90° according to Daimler Regulation DBL 4918.

The AlMgFe phase diagram shows that an Al3Fe phase is formed at a magnesium content of 0-9% by weight and an iron content of 0-3% by weight. It is also known that an Mg5Al8 phase, usually called Al3Mg2, is also formed at a higher Mg content. The solubility of magnesium in aluminium is high enough at 327 °C to dissolve over 7% by weight of magnesium. Thus, the formation of a magnesium-containing phase in the alloy of the invention is not expected. It is known that no significant role in the formation of magnesium is played by AlMg alloys up to a value of 7%, which has also not been confirmed in the present studies.

The ratio of iron is chosen so that sufficient eutectic Al-Al3Fe is present and fine intermetallic phases are formed.

The literature indicates that iron has a decay-reducing effect. In addition, alloys containing 0,4% Si produce a silicon-free Al3Fe eutectic. Silicon is found in the Al phase and no AlFeSi phase is formed. These relationships were confirmed in the present studies. Care should therefore be taken to keep the silicon content sufficiently low, i.e. at about 0.2% Si, otherwise an alpha phase will form and a distant dispersion of the material is expected.

The alloy according to the invention is generally versatile, but is intended for use in structural components in automotive construction. The requirements for crash-relevant structural components can be met already in the casting state. It differs significantly from the alloys used so far in a number of points. The advantage is the high time and thermal stability of the alloy according to the invention. Heat treatments of up to one hour (1h) at 400 °C could be applied without a significant effect on the characteristics of the material reached in the wet state.

The alloy of the invention is also characterised by a good quench capacity in the casting state, which is also not achieved by any alloy on the market so far.

It was found that an alloy compound with a low magnesium content of less than 0.5% by weight of magnesium has a high electrical conductivity of more than 25 m/Ω mm2 [meter per ohm square millimeter].

Additional elements are possible.

Manganese contributes to strength enhancement in limits and can convert brittle AlFeSi beta phases into less harmful AlMn FeSi alpha phases. Beryllium reduces the oxidation propensity of the melt. In the casting of thick-walled components, titanium-boron grain finers are predominantly used. In an embodiment of the alloy according to the invention, copper and/or zinc are added, which significantly affects the strength of the alloy. Hardness occurs when the material reacts by adding copper and/or zinc to heat treatments.

A salt spray mist exchange test (ISO 9227) and an intercrystalline corrosion test (ASTM G110-92) were used to check the corrosion propensity. The composition of the alloy according to the invention is chosen in such a way that a good corrosion resistance can be achieved in the case of the copper- and zinc-free variant.

Comparative examples

The following comparisons are made between the compositions of two examples (alloy variants C and D) of the alloy of the invention, which are given in terms of weight. The mechanical properties (Rm, Rp0.2, A5 and bend angle) of these four alloys were measured on 3 mm die-cast plates. Other

Variante A	0,01	2,01	0,03	0,01	0,003	0,01
Variante B	0,48	2,10	0,04	0,01	0,003	0,01
Variante C	3,94	1,63	0,04	0,01	0,003	0,01
Variante D	6,01	1,56	0,04	0,33	0,003	0,01

Variante A	0,006	0,000	0,000	0,0005	0,000
Variante B	0,006	0,000	0,000	0,0006	0,000
Variante C	0,002	0,000	0,000	0,0008	0,004
Variante D	0,006	0,004	0,030	0,0006	0,003

Results obtained The test shall be carried out in accordance with the procedure described in paragraph 5.2.3.

Variante A	147	73	20,2	91
Variante B	169	82	15,3	68
Variante C	248	120	14,9	60
Variante D	285	150	9,3	45

The bending angle was determined according to the Daimler Regulation DBL 4918 and is a measure of the non-stickness of a material.

The alloy variant B achieved an electrical conductivity of 26.1 m/Ω mm2 in the casting state.

Claims (12)

1. A cast alloy, consisting of:

   iron 0.8-3.0% by weight

   magnesium 2.0 to 7.0%

   manganese 0-2.5% by weight

   beryllium 0-500 ppm

   titanium 0-0.5% by weight

   silicon 0-0.4% by weight

   strontium 0-0.8% by weight

   phosphorus 0-500 ppm

   copper 0-4% by weight

   zinc 0-10% by weight

   0-0.5% by weight of an element or a group of elements selected from the group consisting of chromium, nickel, molybdenum, zirconium, vanadium, hafnium, calcium, gallium and boron, with the remainder being aluminum and unavoidable impurities.
2. The cast alloy according to any one of the preceding claims, characterized by 1.0-2.4% by weight iron.
3. The cast alloy according to any one of the preceding claims, characterized by 1.4-2.2% by weight iron.
4. The cast alloy according to any one of the preceding claims, characterized by 3.0-5.0% by weight magnesium.
5. The cast alloy according to any one of the preceding claims, characterized by 0-0.6% by weight manganese.
6. The cast alloy according to any one of the preceding claims, characterized by 0-100 ppm beryllium.
7. The cast alloy according to any one of the preceding claims, characterized by 0-0.03% by weight strontium.
8. The cast alloy according to any one of the preceding claims, characterized by 0-0.5% by weight zinc.
9. The cast alloy according to any one of the preceding claims, characterized by 0-50 ppm phosphorus.
10. The cast alloy according to any one of the preceding claims, characterized by 0-0.2% by weight copper.
11. Use of a cast alloy according to any one of the preceding claims for die-casting, preferably for die-casting structural components for automotive engineering.
12. A die-cast, crash-relevant structural component for automotive engineering, manufactured from a cast alloy according to any one of the preceding claims 1 to 11.