New high pressure die casting aluminum alloy for high temperature and corrosive applications
a high-pressure die casting and aluminum alloy technology, applied in the field of low copper (cu) or cufree aluminum alloy, can solve the problems of molten metal subject to turbulence, castings made from aluminum alloys, and the inability to effectively artificially age hardening, etc., to achieve enhanced mechanical properties and reduce porosity
Inactive Publication Date: 2017-04-20
GM GLOBAL TECH OPERATIONS LLC
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Benefits of technology
This patent describes a new type of aluminum alloy that can be used for high-pressure die casting and has improved mechanical properties at room and high temperatures. The alloy is also less likely to corrode and can be solution treated effectively. The cast articles made from this alloy have superior mechanical properties after age-hardening treatments. Overall, this disclosure provides a new way to make high-quality aluminum alloys for a range of applications using advanced techniques.
Problems solved by technology
Hence, the injection is under high pressure and the molten metal is subject to turbulence as it is forced into a die and then rapidly solidifies.
Unfortunately, since the air being replaced by the molten alloy has little time to escape, some of it is trapped and porosity results.
Castings also contain pores resulting from gas vapor decomposition products of the organic die wall lubricants and porosity may also result from shrinkage during solidification.
A major drawback of the porosity, particularly induced from entrapped air or gas vapor, resulting from the HPDC process is that castings made from aluminum alloys which ordinarily have the capacity to respond to age-hardening cannot be effectively artificially aged, that is, they cannot attain high supersaturation of hardening elements such as Mg or Cu in the solution prior to artificial aging because no traditional solution treatment can be applied to high pressure die casting parts.
The internal pores containing gases or gas forming compounds in the high pressure die castings expand during conventional solution treatment at elevated temperatures, resulting in the formation of surface blisters on the castings.
The presence of these blisters affects not only the appearance of castings but also dimensional stability and in some cases it can negatively impact particular mechanical properties of HPDC components.
As such, it is nearly impossible to find a conventionally processed HPDC component without large gas bubbles.
In this condition, mechanical properties of the casting, for example material hardness and yield strength, are usually low.
Further aging decreases the hardness / yield strength and the casting becomes overaged due to precipitate coarsening and its transformation of crystallographic incoherency.
This significantly diminishes the subsequent aging potential since the hardening solute solubility decreases significantly with decreasing quench temperature.
As a result, the remaining hardening solute, such as Cu and Mg, available in the aluminum matrix for subsequent aging hardening is very limited.
Therefore, addition of Cu in the current HPDC alloys used in production is not effective in terms of both property improvement and quality assurance.
On the downside, Cu increases the alloy freezing range and decreases feeding capability, leading to a high potential for shrinkage porosity.
More significantly, it generally reduces the corrosion resistance of aluminum castings; and in certain alloys and tempers, it increases stress corrosion susceptibility.
For example, it has been reported that aluminum alloys with a high Cu content (i.e., above about 3-4%) have experienced an unacceptable rate of corrosion, especially in salt-containing environments.
It can be anticipated that the corrosion issue of these alloys will become more significant, particularly when longer warranty time and higher vehicle mileages are required.
However the castings suffer from lower corrosion resistance, a high potential for cast defects and a high material cost due to the Cu.
Essentially Cu-free alloys, such as A356, are known in the art, however they are typically used in sand casting and / or semi-permanent mold casting processes other than HPDC and as formulated, suffer from deficiencies in mechanical properties such as tensile strength.
The alloys of Lin would be unsuitable for HPDC methods.
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[0025]Embodiments of the disclosure relate generally to substantially Cu-free or low-Cu aluminum alloys formulated to provide HPDC casted components capable of age-hardening at elevated temperatures and exhibiting superior mechanical properties and reduced porosity. Unlike aluminum-based Cu containing alloy castings known in the art, the present castings are capable of a full range of temper age-hardening treatments.
[0026]As used herein, “castings” refer generally to aluminum alloy high pressure die castings formed through solidification of aluminum alloy compositions. Thereby, the castings may be referred to herein during any stage of a high pressure die casting process and / or a heat treatment process subsequent to solidification, whether cooling, quenching, aging, or otherwise. Further, castings may include any part, component, product formed via an embodiment of the present invention.
[0027]Further, as used herein, “mechanical property,” and related phrases thereof, refer generall...
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Abstract
Copper-free aluminum alloys suitable for high pressure die casting and capable of age-hardening under elevated temperatures. The alloy includes about 7-15 wt % silicon, about 0 to 0.6 wt % magnesium, about 0 to 1.0 wt % iron, about 0 to 1.0 wt % manganese, about 0 to 1.0 wt % zinc, about 0 to 0.1 wt % strontium, about 0 to 0.5 wt % titanium, about 0 to 0.5 wt % zirconium, about 0 to 0.5 wt % vanadium, about 0 to 0.5 wt % copper, and about 0 to 1.0 wt % nickel, with a balance of aluminum. Methods for making high pressure die castings and castings manufactured from the alloy.
Description
FIELD OF THE INVENTION[0001]The invention relates generally to a low copper (Cu) or Cu-free aluminum alloy formulated for high pressure die casting (HPDC), and the castings therefrom, which are capable of age-hardening at elevated temperatures with reduced porosity, thus possessing superior mechanical properties for applications particularly in the automotive industry.BACKGROUND OF THE INVENTION[0002]HPDC is a cost-effective and wide-spread method for industrial production of metal components requiring precise dimensional consistency, low dimensional tolerances and where a smooth surface finish is important. Manufacturers in the car industry are now increasingly required to produce near-net-shape aluminum components with a combination of high tensile properties and ductility, and HPDC affords the most economic production method for large-scale quantities of small to medium sized components.[0003]In order to avoid discontinuities in the cast component, the molten alloy is injected in...
Claims
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Login to View More IPC IPC(8): C22C21/02B22D17/00C21D1/18C22F1/043C22F1/00
CPCC22C21/02C22F1/043B22D17/00C21D1/18C22F1/002B22D21/007
InventorWANG, QIGUIYANG, WENYINGYE, BING
OwnerGM GLOBAL TECH OPERATIONS LLC