ALLOY COMPOSITION

Description

TECHNICAL FIELD

The disclosure relates to alloy compositions for casting applications.

BACKGROUND

Casting aluminum alloys with high-temperature strength and high electrical conductivity are highly desired to meet the requirements of electrical vehicle motor systems. It is challenging, however, for conventional casting processes to produce material that satisfies both requirements. For example, although Al—Si-based die casting alloys always have a yield strength greater than 100 megapascal (MPa) at 150° C., their electrical conductivities are lower than 40 as measured by the international annealed copper standard (IACS). As a result, such types of cast aluminum alloys are not applicable for electric vehicle traction components. On the other hand, 100 series aluminum alloys, which have high electrical conductivity, have low high-temperature strength (less than 40 MPa) and poor castability.

SUMMARY

In one aspect of the disclosure an aluminum alloy is presented. The aluminum alloy contains from 5 to 12 wt. % cerium, from 0.1 to 1.0 wt. % iron, and a balance of aluminum. The aluminum alloy may further contain from 0.01 to 0.1 wt. % titanium. The yield strength of the aluminum alloy at 150° C. may range from 62 to 80 MPa. The elongation of the aluminum alloy at 150° C. may range from 10 to 26%. The aluminum alloy may have three specific compositions. In one composition, there may be 10 wt. % cerium, 0.1 wt. % iron, and the balance may be aluminum. In another composition, there is 7.5 wt. % cerium, 0.2 wt. % iron, and the balance may be aluminum. In a third composition, there may be 4.5 wt. % cerium, 0.5 wt. % iron, and the balance may be aluminum.

In another aspect of the disclosure a cast aluminum alloy component is presented. The cast aluminum-based component includes 5 to 12 wt. % cerium, 0.1 to 1.0 wt. % iron, and a balance of aluminum. The cast aluminum-based component may further include from 0.01 to 0.1 wt. % titanium. The yield strength of the cast aluminum-based component at 150° C. may range from 62 to 80 MPa. The elongation of the cast aluminum-based component at 150° C. may range from 10 to 26%. The cast aluminum alloy component may have three specific compositions. In one composition, there may be 10 wt. % cerium, 0.1 wt. % iron, and the balance is aluminum. In another composition, there may be 7.5 wt. % cerium, 0.2 wt. % iron, and the balance may be aluminum. In a third composition, there may be 4.5 wt. % cerium, 0.5 wt. % iron, and the balance may be aluminum.

In yet another aspect of the disclosure, a castable alloy is presented. The cast-able alloy has a ternary eutectic mixture of 5 to 12 wt. % cerium, 0.1 to 1.0 wt. % iron, 0.01 to 0.1 wt. % titanium, and a balance of aluminum. The castable alloy may have three specific compositions. In one composition, there is 10 wt. % cerium, 0.1 wt. % iron, and the balance may be aluminum. In another composition, there is 7.5 wt. % cerium, 0.2 wt. % iron, and the balance is aluminum. In a third composition, there is 4.5 wt. % cerium, 0.5 wt. % iron, and the balance may be aluminum. The yield strength of the cast aluminum-based component at 150° C. may be from 62 to 80 MPa. The elongation of the cast aluminum-based component at 150° C. may range from 10 to 26%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show microstructures of alloys with Al dendrites and eutectics;

FIGS. 2A and 2B are ternary phase diagrams of Al—Ce—Fe systems;

FIG. 3 shows the fraction of solid as a function of temperature for an Al—Ce—Fe alloy according to any one or more aspects of the present disclosure;

FIG. 4 shows properties for dumbbell shaped casting molds of Al—Ce—Fe alloys according to aspects of the present disclosure in comparison to two commercially available alloys;

FIG. 5 shows dumbbell shaped casting molds for hot tearing susceptibility assessment, along with the illustration of two types of hot tearing defects including hot tearing crack and break;

FIG. 6 shows 150° C. stress-strain curves for Al—Ce—Fe alloys according to aspects of the disclosure;

FIG. 7 shows a summary of 150° C. tensile testing results and electrical conductivity results for Al—Ce—Fe; and

FIG. 8 shows a traction component containing compositions according to one or more aspects of the disclosure.

DETAILED DESCRIPTION

Embodiments are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale. Some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.

Various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.

Unless otherwise explicitly specified, all numerical values and ranges relating to quantities, measurements, percentages, weights, and similar numerical references within this document are to be understood as being preceded by the term “about.” This applies even in cases where the term “about” is not explicitly used. It is intended that all values and ranges encompass variations that may arise from standard measurement, manufacturing processes, material properties, and intended functionality of aspects of the disclosure. For example, a stated dimension of “10 mm” should be interpreted as “about 10 mm.” Similarly, when a composition is described as having “5 wt. % of a component,” it is to be understood as “about 5 wt. % of a component.” Furthermore, when numerical values are presented as a range, such as “100 to 200 units,” this range should be interpreted to effectively mean “about 100 to about 200 units.” Such variations are implicitly incorporated within the scope of the present disclosure.

This disclosure relates to the development and application of aluminum (Al) alloys tailored for a variety of casting processes, including but not limited to high-pressure die casting, permanent mold casting, and sand casting. These alloys are configured for direct use in their as-cast condition. Although additional thermal treatments are not mandatory for achieving requisite mechanical strength and electrical conductivity, they may be employed to enhance the alloys' properties.

The composition of these Al alloys includes in some examples 5 wt. % to 12 wt. % cerium (Ce), 0.1 wt. % to 1.0 wt. % iron (Fe), and an optional addition of 0.01 wt. % to 0.1 wt. % titanium (Ti). Ce enhances strength at various temperatures and, alongside Al, forms eutectics that diminish hot-tearing susceptibility, thus improving castability. Fe contributes similarly by enhancing strength and reducing both hot-tearing and die-soldering tendencies. Ti's role is to refine Al's grain structure, further amplifying strength. Notably, these alloys achieve electrical conductivity within an electrical conductivity range of 48-53 as measured by the international annealed copper standard (IACS) and demonstrate 150° C. yield strengths of 62-80 megapascal (MPa).

FIGS. 1A-1C show the microstructures of three representative Al—Ce—Fe alloys: A1-4.5 wt. % Ce-0.5 wt. % Fe, Al-7.5 wt. % Ce-0.2 wt. % Fe, and Al-10.0 wt. % Ce-0.1 wt. % Fe. All compositions display a typical as-cast structure consisting of primary Al dendrites surrounded by inter-dendritic regions containing ternary eutectic phases. The eutectic volume fraction progressively increases with higher Ce content, from 4.5 wt. % to 10 wt. %. This microstructural evolution plays a role in enhancing the alloys' mechanical properties and hot tearing resistance. The presence of a higher proportion of eutectic phases helps to distribute strain more uniformly during solidification, reducing the chance of hot tearing defects.

FIGS. 2A and 2B show the ternary phase diagrams of the Al—Ce—Fe system. The full compositional map in FIG. 2A identifies an invariant ternary eutectic point at 637° C., corresponding to the reaction: liquid→Fcc-Al+Al11Ce3+Al10Fe2, for an alloy containing Al-8.7 wt. % Ce-0.8 wt. % Fe. The dashed lines delineate a range of hypoeutectic and hypereutectic compositions near this invariant point, which are prime candidates for casting due to their favorable solidification characteristics. FIG. 2B provides a magnified view of the Al-rich corner, plotting the eutectic point and several alloys of interest, such as Al13M4 (Al-19 wt. % Ce-1.5 wt. % Fe) and Al10M12 (Al-10 wt. % Ce-2 wt. % Fe).

FIG. 3 shows thermodynamic calculations of the solid fraction as a function of temperature for three Al—Ce—Fe alloys: Al-4.5 wt. % Ce-0.5 wt. % Fe, Al-7.5 wt. % Ce-0.2 wt. % Fe, and Al-10.0 wt. % Ce-0.1 wt. % Fe. The temperature range for hot tearing susceptibility lies between 80% and 100% solid, marked as the “Hot Tearing Susceptible Zone.” Within this region, the alloy exhibits low ductility and insufficient liquid feeding, leading to an increased chance of hot tearing defects. The Al—Ce—Fe compositions proposed are shown to have relatively narrow susceptible zones, indicating a lower probability of hot tearing during solidification. This computational analysis complements the experimental findings and provides insights into the alloys' solidification behavior, allowing for the optimization of composition and process parameters to mitigate hot tearing chances.

FIG. 4 shows the hot tearing assessment results from the dumbbell-shaped casting molds. The table compares the performance of the Al—Ce—Fe alloys against a reference Al5.0Ni0.3Fe alloy and the commercial Al7Si2.5 Mg. The occurrence of cracks and breaks is tabulated for each alloy at rod diameters of 8 mm, 6 mm, and 4 mm. The Al7Si2.5 Mg alloy consistently exhibits breaks at all diameters, highlighting its poor hot tearing resistance. In contrast, the Al—Ce—Fe alloys only show minor cracking at the 6 mm and 4 mm sizes, with no defects observed at the larger 8 mm diameter. These results underscore the superior hot tearing resistance of the disclosed Al—Ce—Fe compositions, validating their suitability for challenging casting applications where hot tearing is a concern.

FIG. 5 shows the dumbbell-shaped casting mold used for assessing the hot tearing susceptibility of aluminum alloys. The experimental results feature varying rod diameters (8 mm, 6 mm, and 4 mm) to induce hot tearing defects, which can manifest as either cracks or complete breaks. The occurrence of these defects is indicative of an alloy's resistance to hot tearing during solidification.

FIG. 6 shows the 150° C. stress-strain curves for the proposed Al—Ce—Fe alloys, demonstrating their high-temperature strength. The alloys exhibit yield strengths ranging from 47.4 MPa to 74.4 MPa and ultimate tensile strengths between 112 MPa and 148 MPa at 150° C. The Al-7.5 wt. % Ce-0.2 wt. % Fe and Al-10.0 wt. % Ce-0.1 wt. % Fe compositions, in particular, achieve yield strengths exceeding 60 MPa, meeting the requirements for electric vehicle traction component applications. These enhanced mechanical properties are attributed to the presence of thermally stable eutectic phases, which provide effective strengthening mechanisms even at elevated temperatures. The stress-strain curves also reveal good ductility, with elongation values ranging from 15.5% to 19.1%, indicating that the alloys can accommodate significant plastic deformation before tearing.

FIG. 7 shows the 150° C. tensile properties and electrical conductivity results for the Al—Ce—Fe alloys. The yield strength, ultimate tensile strength, and elongation data confirm the alloys' high-temperature performance, as discussed in relation to FIG. 6, which shows the electrical conductivity values for all the studied compositions exceed 48 IACS, reaching up to 51 IACS for the Al-7.5 wt. % Ce-0.2 wt. % Fe alloy. This combination of high electrical conductivity and strong mechanical properties at elevated temperatures sets these proposed Al—Ce—Fe alloys apart from conventional casting alloys. The ability to maintain conductivity while significantly enhancing strength makes these alloys particularly attractive for applications in traction components and systems that operate at elevated temperatures, such as electric vehicle motors.

FIG. 8 shows a traction component 10. The traction component 10 contains material 12. The material 12 may be any one of several aluminum alloy compositions proposed, configured to enhance mechanical performance and durability of the traction component 10. These compositions may range from 5 to 12 wt. % cerium, 0.1 to 1.0 wt. % iron, and the remaining balance being aluminum. Optionally, these alloys may include from 0.01 to 0.1 wt. % titanium to further enhance their properties. The selection of components in the material 12 helps the traction component 10 withstand the conditions of its application, exhibiting high yield strength and elongation at elevated temperatures, which maintains integrity and functionality under stress.

While exemplary embodiments are contemplated and described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of these disclosed materials.

As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, case of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.