Corrosion-Resistant Aluminum Alloy

The present disclosure relates to an electronics module housing, and more particularly, to an electronics module housing including an integrated part electronics (IPE) component formed of a corrosion-resistant aluminum alloy.

Aluminum exhibits a combination of high corrosion resistance, thermal conductivity, and machinability, and is thus a desirable material for use in the manufacture of electrical and vehicle components. Aluminum alloys for casting applications typically include silicon or other metals as alloying elements to increase strength and other desirable qualities.

Many metals and alloys, including aluminum, are affected by crevice corrosion, which is localized corrosion of a metal or alloy at or immediately adjacent to an area that is shielded from environmental exposure because of close proximity of the metal or alloy to a surface of another material or an adjacent surface of the same metal or alloy. Crevice corrosion is among the most damaging forms of corrosion.

Crevice geometries may be found on a wide variety of structures and components, for example flanges, threaded connections, lap joints, and under damaged coatings. For an electronics module housing, crevice corrosion tends to occur at sealing or mating surfaces. Current methods for improving crevice corrosion performance of aluminum-made electronics module housing include applying aluminum alloys with reduced copper content as it is believed that copper is the main alloying element that causes degraded corrosion performance. For instance, the copper content in A380 alloy ranges from 3-4 mass %, showing unsatisfactory performance in component-level crevice corrosion testing. However, commercially available premium aluminum alloys including A360 and 43400 alloys with reduced copper content of 0-0.6 wt. % and 0-0.08 wt. % still exhibit crevice corrosion. Hence, the known alloys are usually treated with anodization or an E-coat to pass the component-level crevice corrosion test, but the added coatings and anodization surface treatment increase cost.

While prior art methods and systems attempt to minimize crevice corrosion in aluminum and aluminum alloys and may achieve their particular purpose, a need still exists for a new and improved aluminum and aluminum alloy that minimizes and prevents crevice corrosion. Accordingly, a corrosion-resistant aluminum and aluminum alloy is needed.

According to several aspects of the present disclosure, an electronics module housing is provided. The electronics module housing includes a high-pressure die cast integrated power electronics (IPE) housing component having at least one coating-free mating surface. The integrated power electronics housing component is formed from an aluminum alloy including silicon between 6.5 wt. % and 7.5 wt. %, copper between 0.05 wt. % and 0.30 wt. %, magnesium between 0.1 wt. % and 0.6 wt. %, iron between 0.20 wt. % and 1.50 wt. %, chromium less than 0.30 wt. %, and manganese than 0.15 wt. %.

In accordance with another aspect of the disclosure, the electronics module housing includes a corrosion rate (K) of the aluminum alloy less than or equal to 0.003.

In accordance with another aspect of the disclosure, the electronics module housing includes a corrosion rate (K) defined as K=−0.0251+0.0064 (Fe wt. %)+0.0844(Cu wt. %)+0.1041 (Cr wt. %).

In accordance with another aspect of the disclosure, the electronics module housing includes an aluminum alloy satisfying the equation 2.7 (Cr wt. %)+1.44 (Mn wt. %) +(Fe wt. %) is greater than 0.8.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, iron between 0.25 wt. % and 0.60 wt. %, and magnesium between 0.5 wt. % and 0.6 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.05 wt. % and 0.10 wt. %, copper between 0.1 wt. % and 0.15 wt. %, and iron between 0.25 wt. % and 0.65 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.05 wt. % and 0.10 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.1 wt. % and 0.15 wt. %, and iron between 0.25 wt. % and 0.65 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.05 wt. % and 0.10 wt. %, copper between 0.1 wt. % and 0.15 wt. %, iron between 0.25 wt. % and 0.65 wt. %, and magnesium between 0.5 wt. % and 0.6 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes copper greater than 0.05 wt. % and iron greater than 0.2 wt. %.

According to several aspects of the present disclosure, a method for forming a high-pressure die cast integrated power electronics (IPE) housing component is provided. The method includes forming an aluminum alloy in a molten state and casting the molten aluminum alloy by a high pressure die cast process to form a cast structure. The aluminum alloy includes silicon between 6.5 wt. % and 7.5 wt. %, copper between 0.05 wt. % and 0.30 wt. %, magnesium between 0.1 wt. % and 0.6 wt. %, iron between 0.20 wt. % and 1.50 wt. %, chromium less than 0.30 wt. %, and manganese than 0.15 wt. %.

In accordance with another aspect of the disclosure, the cast structure is an individual IPE housing component, and each IPE housing component has at least one coating-free mating surface.

In accordance with another aspect of the disclosure, the method includes an aluminum alloy having a corrosion rate (K) less than or equal to 0.003.

In accordance with another aspect of the disclosure, the method includes an aluminum alloy having a corrosion rate (K) defined as K=−0.0251+0.0064 (Fe wt. %) +0.0844 (Cu wt. %)+0.1041 (Cr wt. %).

In accordance with another aspect of the disclosure, the aluminum alloy includes copper greater than 0.05 wt. % and iron greater than 0.2 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In accordance with another aspect of the disclosure, the aluminum alloy includes chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, iron between 0.25 wt. % and 0.60 wt. %, and magnesium between 0.5 wt. % and 0.6 wt. %.

According to several aspects of the present disclosure, an electronics module housing is provided. The electronics module housing includes a high-pressure die cast integrated power electronics (IPE) housing component having at least one coating-free mating surface. The integrated power electronics housing component is formed from an aluminum alloy including silicon between 6.5 wt. % and 7.5 wt. %, copper between 0.05 wt. % and 0.30 wt. %, magnesium between 0.1 wt. % and 0.6 wt. %, iron between 0.20 wt. % and 1.50 wt. %, chromium less than 0.30 wt. %, and manganese than 0.15 wt. %. A corrosion rate (K) of the aluminum alloy is less than or equal to 0.003, where K=−0.0251+0.0064 (Fe wt. %)+0.0844 (Cu wt. %)+0.1041 (Cr wt. %). Additionally, the aluminum alloy satisfies the equation 2.7 (Cr wt. %)+1.44 (Mn wt. %)+(Fe wt. %) is greater than 0.8%.

In accordance with another aspect of the disclosure, the electronics module housing includes an IPE housing component having a tensile yield strength between 160 MPa and 180 MPa and a tensile elongation-to-fracture of between 3%-6% in an as-cast state.

Further areas of applicability of the present disclosure will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

The above features and advantages, and other features and advantages, of the presently disclosed system and method are readily apparent from the detailed description, including the claims, and examples when taken in connection with the accompanying drawings.

Reference will now be made in detail to several examples of the disclosure that are illustrated in accompanying drawings. Whenever possible, the same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

For electronics module housing, for example an integrated part electronics (IPE) component formed of a corrosion-resistant aluminum alloy, crevice corrosion tends to occur at sealing and mating surfaces. Many current aluminum alloys, including A360, A380, and premium 43400 alloys have been shown to fail crevice corrosion raising concerns for potential failure of electronic components.

illustrates a perspective view of an electronics module housing, in accordance with the present disclosure. The electronics module housingcan include an integrated power electronics (IPE) housing componentformed from high pressure die casting, for example. An IPE module (not shown), housed within the integrated power electronics (IPE) housing component, includes an electric drive unit (EDU) or other electrical/mechanical modules that combine power electronics and motor components within a single assembly. The electronics module housingand/or the integrated power electronics (IPE) housing componentcan be utilized in automotive applications as well as high-performance computing, communications, and industrial systems.

The electronics module housingis formed of an aluminum alloy and has at least one coating-free sealing or mating surface. A coating-free mating surfaceincludes a surface that is configured to abut a substrate or chassis, which supports the electronics module housing. For example, the coating-free mating surfacemay include a lidcoupled to a wall, or a wallcoupled to a substrate. Preferably, the electronics module housingincludes no coating at any mating surfaceof the housing.

Crevice corrosion performance of electronics module housingcan be evaluated via measuring corrosion penetration length on the mating surface, under designated testing environment.

The term “aluminum alloy” refers to a material that comprises, by weight, greater than or equal to 80% or, more preferably, greater than or equal to 90% aluminum (Al) and one or more other elements selected impart certain desirable properties to the material that are not exhibited by pure aluminum.

An aluminum alloy composition for casting shaped aluminum alloy parts may include, in addition to aluminum, alloying elements of silicon (Si), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), magnesium (Mg), chromium (Cr), and titanium (Ti). The respective amounts or Si, Cr, Cu, and Mg in the alloy are selected to provide the alloy with certain desirable properties during casting and with the ability to develop a desired microstructure during a subsequent heat treatment process.

The corrosion resistance of an aluminum alloy is strongly related to its alloying content. For example, the amount of silicon in the aluminum alloy is selected to provide the molten alloy with suitable fluidity for casting, a relatively low melting temperature, excellent dimensional stability, and low thermal expansion, all of which are required for excellent castability. In the aluminum alloys traditionally used for casting electronics module housing, such as A380, A360 and 43400 aluminum alloys, silicon content ranges from 9 mass % to 11 mass % for excellent castability. However, a higher silicon content, along with the existence of transition metal elements like iron (Fe), manganese (Mn), chromium (Cr) and copper (Cu), results in the formation of a larger volume of intermetallic particles embedded in the aluminum matrix which may act as cathode to induce corrosion of the aluminum matrix. Silicon content ranges from 6.5 mass % to 7.5 mass % will impart a better balance between castability and corrosion resistance for the application of electronics module housing.

In addition, the respective amounts of Fe, Cr, Cu, and Magnesium (Mg) in the aluminum alloy are selected to provide the alloy with the ability to develop a multiphase microstructure when subjected to a suitable heat treatment process that includes a solution heat treatment stage and a subsequent artificial aging heat treatment stage. Among them, Mg has relatively minor impact on corrosion resistance. The content of Mg is dependent on the requirement of strength properties and normally ranges from 0.1 mass % to 0.6 mass %. Fe, Cr and Cu will have significant adverse impacts on corrosion resistance. Moreover, allowing a higher content of Fe, Cr and Cu in aluminum alloy is often desirable as more low-cost scrap can be used in the production for cost-saving.

Additionally, elements not intentionally introduced into the composition of the aluminum alloy may be inherently present in the alloy in relatively small amounts (e.g., less than 0.2 wt. %, preferably less than 0.05 wt. %, and more preferably less than 0.01 wt. %). These elements may be present, for example, as impurities in the raw materials used to prepare the aluminum alloy. In examples where the aluminum alloy is referred to as comprising one or more alloying elements (e.g., one or more of Si, Cr, Cu, Mg, Ti, and/or Sr) and aluminum as balance, the term “as balance” does not exclude the presence of additional elements not intentionally introduced into the composition of the aluminum alloy but nonetheless inherently present in the aluminum alloy in relatively small amounts, for example as impurities.

For metals that have a low oxidation potential, including elemental aluminum, a cathodic reaction of hydrogen evolution is possible during free corrosion. In aluminum electronic housing components, hydrogen evolution indicates crevice corrosion of the aluminum housing components, often on or at mating or sealing surfaces. Crevice corrosion risk increases with active metal, improper crevice geometry, and component location. For evaluating crevice corrosion performance risk in a fast manner, hydrogen released from the corrosion of aluminum matrix was collected from a lab immersion test using samples of aluminum alloys with a size of 1 centimeter (cm)×1 cm×0.5 cmconducted in a 3.5 wt. % NaCl solution at room temperature for one week to determine an impact of iron (Fe), copper (Cu), and chromium (Cr) on corrosion resistance of the aluminum alloys. As shown in Table 1 below, six alloys were tested in a lab immersion test in which alloys A, B, C, D, E were Al-Si alloys containing 7 mass % Si and varied levels of Cr, Fe and Cu. A360 alloy was also tested as baseline.illustrates the hydrogen evolution rates of the tested alloys. Hydrogen evolution rate can be calculated by linear fitting the data to get the slope for ranking corrosion resistance of various aluminum alloys. A smaller slope indicates a better corrosion resistance. According to the results, alloys E, A and D have better corrosion resistance than A360 alloy.

A formula has been developed to correlate Cr, Cu and Fe contents of an aluminum alloy to its corrosion rate K in lab immersion test as K=−0.0251+0.0064 (Fe wt. %)+0.0844 (Cu wt. %)+0.1041 (Cr wt. %), where Fe, Cu and Cr are mass percentages contained in the alloy.

Alloy E, as shown in Tableabove, was selected to cast electronics module housingfor component-level crevice corrosion testing and passed with very limited crevice corrosion penetration at mating surfaces. When K ≤0.003 milliliters per square centimeter hour (ml/cm·hr), the Al-Si-Cr-Fe-Cu alloy provides sufficient corrosion resistance for satisfying crevice corrosion performance for electronics module housing.

In an example, the aluminum alloy composition for casting shaped aluminum alloy parts has a hydrogen evolution rate K in lab immersion test of less than or equal to 0.0030 milliliters per square centimeter hour (mL/cm·hr). In an additional example, the K satisfies the equation −0.0251+(0.0064·Fe·100)+(0.0844−Cu−100)+(0.1041·Cr·100), where Fe, Cu and Cr are weight and/or mass percentages contained in the alloy. In an additional example, which facilitates a high ratio of scrap in raw material production, the aluminum alloy includes equal to or greater than 0.05 wt. % copper (Cu) and equal to or greater than 0.2 wt. % iron (Fe).

In an example, the aluminum alloy may include, by weight, silicon between 6.5 wt. % and 7.5 wt. %, copper between 0.05 wt. % and 0.30 wt. %, magnesium between 0.1 wt. % and 0.6 wt. %, iron between 0.20 wt. % and 1.5 wt. %, chromium more than 0 wt. % and less than 0.30 wt. %, and manganese more than 0 wt. % and less than 0.15 wt. %. For satisfying die-sticking resistance required by high pressure die casting process, 2.7·Cr·100+1.44·Mn·100+Fe>0.8, where Fe, Mn and Cr are mass percentages contained in the alloy.

In another example, the aluminum alloy may include, by weight, chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In another example, the aluminum alloy may include, by weight, chromium between 0.1 wt. % and 0.15 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.

In another example, the aluminum alloy may include, by weight, chromium between 0.1 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, iron between 0.25 wt. % and 0.60 wt. %, and magnesium between 0.5 wt. % and 0.6 wt. %.

In another example, the aluminum alloy may include, by weight, chromium between 0.05 wt. % and 0.10 wt. %, copper between 0.1 wt. % and 0.15 wt. %, and iron between 0.25 wt. % and 0.65 wt. %.

In another example, the aluminum alloy may include, by weight, chromium between 0.05 wt. % and 0.10 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.1 wt. % and 0.15 wt. %, and iron between 0.25 wt. % and 0.65 wt. %.

In an example, the aluminum alloy may include, by weight, chromium between 0.05 wt. % and 0.10 wt. %, manganese between 0.05 wt. % and 0.15 wt. %, copper between 0.05 wt. % and 0.1 wt. %, and iron between 0.2 wt. % and 0.60 wt. %.