CN111809083B

CN111809083B - Aluminum alloy composition for simplifying semi-solid casting process and semi-solid casting method

Info

Publication number: CN111809083B
Application number: CN201910294202.4A
Authority: CN
Inventors: 胡斌; 王攀
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2019-04-12
Filing date: 2019-04-12
Publication date: 2022-06-24
Anticipated expiration: 2039-04-12
Also published as: CN111809083A; US20200325558A1

Abstract

An aluminum alloy composition and a semi-solid casting method simplifying a semi-solid casting process, the aluminum alloy having about 0.03 to about 0.50 wt% niobium (Nb), about 0.03 to about 0.50 wt% vanadium (V), about 0.03 to about 0.50 wt% titanium (Ti), greater than 0 to about 0.50 wt% boron (B), and the balance aluminum (Al) and impurities. The alloy includes a weight percent ratio of (Nb + V)/Ti of about 1 to about 5, preferably about 2 to about 3. The alloy may include (Nb + V + Ti)/B in a weight percent ratio of about 1 to about 15 (preferably about 5 to about 10). The aluminum alloy may be formed by incorporating 1 part by weight of a master alloy (grain refiner) having about 1.5 to about 4.0 wt% niobium (Nb), about 0.5 to about 2.0 wt% titanium (Ti), and about 0.2 to about 0.8 wt% boron (B) into about 27 to 80 parts of a conventional aluminum alloy.

Description

Aluminum alloy composition for simplifying semi-solid casting process and semi-solid casting method

Technical Field

The present disclosure relates to aluminum alloys, and more particularly to aluminum alloys for semi-solid casting.

Background

Casting metal into useful shapes includes: the metal is heated to a temperature above its melting point, the molten metal is placed in a mold, and the metal is cooled to a temperature below its melting point. The metal solidifies and forms the shape of the mold and is thereafter removed from the mold. Semi-solid casting is a known metal casting process that uses a metal pour in the form of a slurry that is partially solid and partially liquid (also referred to as a semi-solid slurry). Aluminum components manufactured by semi-solid casting, particularly in a high pressure die casting process, are desirable in the aircraft, telecommunications, and automotive industries because of the relatively low porosity, low weight, and high strength characteristics of semi-solid cast components compared to liquid aluminum cast components.

Semi-solid cast aluminum components are traditionally produced by thixocasting, a process that utilizes pre-cast billets having a globular microstructure. Induction heating is commonly used to heat a pre-cast billet to a semi-solid temperature range, and die casting machines are used to inject a semi-solid slurry into a hardened steel mold. The disadvantage of thixocasting is that it is an expensive and time consuming process due to the additional steps of producing the pre-cast billet and heating the pre-cast billet to the semi-solid temperature range.

An alternative to thixocasting is rheocasting, which is a process in which liquid aluminum is cooled to within a semi-solid temperature range while being vigorously stirred to produce a globular microstructure (primary alpha-aluminum grains) for semi-solid forming. Rheocasting produces a semi-solid slurry directly from a liquid, thereby eliminating the steps of producing and inductively heating a pre-cast billet. However, during the cooling and stirring steps of the casting process, oxides and inclusions may form in the semi-solid slurry and become trapped in the finished casting. In addition, rheocasting requires the production of a semi-solid slurry and its delivery to a casting mold.

Thus, while current semi-solid aluminum casting processes and aluminum casting alloys used in such processes achieve their intended purpose, there remains a need for more efficient semi-solid casting processes and aluminum alloys that perform such processes.

Disclosure of Invention

According to several aspects, an aluminum alloy composition suitable for semi-solid casting. The aluminum alloy includes about 0.03 wt.% to about 0.50 wt.% niobium (Nb), about 0.03 wt.% to about 0.50 wt.% vanadium (V), about 0.03 wt.% to about 0.50 wt.% titanium (Ti), and a remainder or balance consisting of aluminum (Al) and impurities.

In another aspect of the present disclosure, the aluminum alloy further includes a weight percent ratio of (Nb + V)/Ti of about 1 to about 5 (preferably about 2 to about 3).

In another aspect of the present disclosure, the aluminum alloy further includes greater than 0 wt.% to about 0.50 wt.% boron (B).

In another aspect of the present disclosure, the aluminum alloy further includes a weight percent ratio of (Nb + V + Ti)/B of about 1 to about 15 (preferably about 5 to 10).

In another aspect of the present disclosure, the aluminum alloy further includes about 4.00 wt.% to about 10.00 wt.% silicon (Si), about 0.01 wt.% to about 3.00 wt.% copper (Cu), about 0.10 wt.% to about 1.00 wt.% magnesium (Mg), and about 0.01 wt.% to about 0.03 wt.% strontium (Sr).

According to several aspects, a method of semi-solid casting is disclosed. The method comprises the following steps: heating the aluminum alloy until the aluminum alloy is converted to a liquid aluminum alloy; cooling the liquid aluminum alloy until the liquid aluminum alloy is converted into a semi-solid aluminum alloy; pouring the semi-solid aluminum alloy into a casting mold; cooling the semi-solid aluminum alloy until the semi-solid aluminum alloy is transformed into a solid aluminum alloy in the casting mold. The aluminum alloy implementing the method includes about 0.03 wt.% to about 0.50 wt.% niobium (Nb), about 0.03 wt.% to about 0.50 wt.% vanadium (V), about 0.03 wt.% to about 0.50 wt.% titanium (Ti), and a remainder including aluminum (Al) and impurities.

In another aspect of the present disclosure, the aluminum alloy further includes a weight percent ratio of (Nb + V + Ti)/B of about 1 to about 15 (preferably about 5 to about 10).

In another aspect of the present disclosure, the aluminum alloy further includes about 4.00 wt.% to about 10.00 wt.% silicon (Si), about 0.01 wt.% to about 3.00 wt.% copper (Cu), about 1.00 wt.% magnesium (Mg), about 0.03 wt.% strontium (Sr), greater than 0.0 wt.% but less than or equal to about 0.50 wt.% manganese (Mn), and greater than 0.0 wt.% but less than or equal to about 0.50 wt.% chromium (Cr).

In another aspect of the present disclosure, the step of heating the solid aluminum alloy until the aluminum alloy is converted to a liquid aluminum alloy includes heating the solid aluminum alloy to a liquidus range between about 30 ℃ to about 80 ℃.

In another aspect of the present disclosure, the step of cooling the liquid aluminum alloy until the aluminum alloy is transformed into a semi-solid aluminum alloy includes cooling the liquid aluminum alloy at a rate greater than 5 ℃ per second.

According to several aspects, a master alloy is disclosed. The master alloy may be incorporated into a conventional aluminum alloy in a ratio of 1 part master alloy to 27 to 80 parts conventional alloy by weight to produce an aluminum alloy suitable for semi-solid casting. The master alloy includes about 1.5 to 4.0 wt.% niobium (Nb), about 0.5 to 2.0 wt.% titanium (Ti), about 0.2 to about 0.8 wt.% boron (B), and a remainder including aluminum (Al) and impurities.

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

Drawings

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a table illustrating aluminum alloy compositions suitable for semi-solid casting according to an exemplary embodiment;

FIG. 2 is a table illustrating grain refiner compositions according to an exemplary embodiment;

FIG. 3 is an enlarged view of the surface finish of a laboratory sample of an aluminum alloy without a grain refiner element;

FIG. 4 is an enlarged view of a surface finish of an aluminum alloy laboratory sample having a grain refiner element according to an exemplary embodiment; and

fig. 5 is a flow chart depicting steps of a semi-solid aluminum casting method.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. The illustrated embodiments are disclosed with reference to the accompanying drawings, wherein like reference numerals represent corresponding parts throughout the drawings. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular features. Specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts.

Referring to fig. 1, a table of compositions of aluminum alloys enabling a simplified semi-solid casting process is shown. The aluminum alloy comprises the following components in percentage by weight: about 4.00 wt% to about 10.00 wt% silicon (Si), about 0.10 wt% to about 0.50 wt% iron (Fe), about 0.01 wt% to about 3.00 wt% copper (Cu), about 0.10 wt% to about 1.00 wt% magnesium (Mg), about 0.03 wt% to about 0.50 wt% niobium (Nb), about 0.03 wt% to about 0.50 wt% vanadium (V), about 0.03 wt% to about 0.50 wt% titanium (Ti), from greater than 0 wt% to about 0.50 wt% boron (B), about 0.01 wt% to about 0.03 wt% strontium (Sr), greater than 0.0 wt% but less than or equal to about 0.50 wt% manganese (Mn), greater than 0.0 wt% but less than or equal to about 0.50 wt% chromium (Cr), and the balance aluminum (Al) and impurities.

Preferably, the Mg is between about 0.3 wt% to about 0.5 wt% to enable the formation of magnesium silicide (Mg)₂Si) precipitate. Preferably, Cu is between about 0.3 wt% to about 1.0 wt% to enable formation of Q-phase precipitates. Preferably, in the semi-solid casting process, the silicon is between about 5.0 wt.% and about 8.0 wt.% for a wide solidus-liquidus range. The preferred range of iron is determined by the ductility requirements of the casting produced.

The aluminum alloy contains Nb, V, Ti, and B to refine grains by forming a spherical microstructure. It has been found that certain combinations of Nb, V, Ti and B weight ratios in aluminum alloys cause abnormal grain refinement in the aluminum alloy, enabling the aluminum alloy to be used for semi-solid casting without the additional steps of precasting the billet and reheating the billet to the melting temperature, or the step of cooling the liquid aluminum to the semi-solid temperature range while vigorously stirring or agitating the liquid aluminum to produce the desired globular microstructure in the semi-solid state.

The ratio of the combined weight percent of Nb and V to the weight percent of Ti [ (Nb + V)/Ti ] should be controlled to be in the range of from about 1 to about 5, preferably from about 2 to about 3. In other words, the combined wt.% for each 1 wt.% of Ti, Nb, and V is about 1 to 5 wt.%, preferably 2 to 3 wt.%, which makes the aluminum alloy suitable for simplified semi-solid casting.

The ratio of the combined weight percent of Nb, V and Ti to the weight percent of B [ (Nb + V + Ti)/B ] should be controlled to be in the range of from about 1 to about 15, preferably from about 5 to about 10. In other words, the combined wt.% for each 1 wt.% of B, Nb, V and Ti is about 1 to 15 wt.%, preferably 5 to 10 wt.%, which makes the aluminum alloy suitable for simplified semi-solid casting.

Referring to fig. 2, a table of compositions of grain refiners for producing aluminum alloys to achieve a simplified semi-solid casting process is shown. Grain refiners (also known as master alloys) may incorporate commercially available aluminum alloys, including but not limited to a380, a383, and a360 aluminum alloys, to convert the commercially available aluminum alloys to form a spherical microstructure. The master alloy includes about 1.5 wt% to about 4.0 wt% niobium (Nb), about 0.5 wt% to about 2.0 wt% titanium (Ti), about 0.2 wt% to about 0.8 wt% boron (B), and the balance aluminum (Al) and impurities.

The master alloy may be incorporated into commercially available aluminum alloys in a ratio of about 1: 80 to 1: 27 by weight to produce the presently disclosed aluminum alloys. In other words, an aluminum alloy suitable for the simplified semi-casting process may be prepared by adding 1 part by weight of the master alloy to about 27 to 80 parts of a conventional aluminum alloy.

Fig. 3 shows an enlarged view of the surface finish of a laboratory sample of an aluminum alloy 300 without grain refining elements, according to an exemplary embodiment. The aluminum alloy 300 exhibits a dendritic microstructure 302 that is unsuitable for semi-solid casting.

FIG. 4 shows an enlarged view of the surface finish of a laboratory sample of an aluminum alloy 400 having a fine-grained microstructure 402 according to an example embodiment. The fine grain microstructure 402 is finer than the dendritic microstructure 302 of fig. 3.

Fig. 5 is a flow chart depicting steps of a semi-solid aluminum casting method 500 using a modified aluminum alloy having the composition shown in fig. 1. The method comprises the following steps: step 502, heating the solid alloy until the solid alloy is transformed into a liquid alloy; step 504, cooling the liquid alloy until the liquid alloy is transformed into a semi-solid alloy and pouring the semi-solid alloy into a casting mold; and step 506, cooling the semi-solid alloy until the semi-solid alloy is transformed into a solid alloy in the casting die.

Step 502 of heating the solid alloy until the solid alloy transforms into a liquid alloy includes heating the solid alloy to a liquidus range between about 30 ℃ and about 80 ℃. The step 504 of cooling the liquid alloy until the alloy transitions to a semi-solid alloy includes cooling the liquid alloy at a rate greater than 5 c per second. The cooling rate enables the formation of a spherical microstructure as shown in fig. 4.

Digital data has been presented herein in a range format. The term "about" as used herein is well known to those skilled in the art. Alternatively, the term "about" includes +/-0.05 by weight. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. While examples have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and examples for practicing the disclosed methods within the scope of the appended claims.

The description of the disclosure is merely exemplary in nature and variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.

Claims

1. An aluminum alloy, comprising:

4.00 to 10.00 wt% silicon (Si);

0.10 to 0.50 wt% iron (Fe);

0.01 to 3.00 wt% of copper (Cu);

0.10 to 1.00 wt% magnesium (Mg);

0.03 to 0.50% by weight of niobium (Nb);

0.03 to 0.50% by weight of vanadium (V);

0.03 to 0.50 wt% titanium (Ti);

more than 0 to 0.50 wt% boron (B);

0.01 to 0.03% by weight of strontium (Sr);

greater than 0.0 wt% but less than or equal to 0.50 wt% manganese (Mn);

greater than 0.0% but less than or equal to 0.50% by weight chromium (Cr);

and the balance being aluminum (Al) and impurities;

wherein the weight percentage ratio of (Nb + V + Ti)/B is 10 to 15; the ratio of (Nb + V)/Ti is 1 to 5 by weight percent.

2. The aluminum alloy of claim 1, wherein the (Nb + V)/Ti weight percent ratio is 2 to 3.