Free machining aluminum alloy with high melting point machining constituent and method of use

• US 6,416,598 B1
• Filed: 04/20/1999
• Issued: 07/09/2002
• Est. Priority Date: 04/20/1999
• Status: Expired due to Fees

• Current Assignee: Reynolds Metals Company (Howmet Aerospace, Inc.)
• Original Assignee: Reynolds Metals Company (Howmet Aerospace, Inc.)
• Inventors: Sircar, Subhasish
• Primary Examiner(s): King, Roy
• Assistant Examiner(s): WILKINS III, HARRY D
• Application Number:
  US09/295,160
• Time in Patent Office: 1,176 Days
• Field of Search: 148/437, 148/688, 148/549, 420/528
• US Class Current: 148/688
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: C22C 1/1036 starting from a melt
• CPC Class Codes: C22C 1/1047 by mixing and casting liquid metal matrix composites
• CPC Class Codes: C22C 32/00 Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ

Abstract

A free machining aluminum alloy contains an effective amount of one or more high melting point constituents that provide enhanced machining capability. The high melting point constituents occupy from about 0.1 to about 3.0 volume percent of the aluminum alloy. The constituents can be any material that is essentially insoluble in the aluminum alloy matrix so as to form a discontinuity and one that will resist deformation during machining to enhance the formation of voids between the matrix and the free machining constituents. The constituents include elements, nitrides, oxides, borides, carbides, silicides, aluminides and combinations thereof that have a high melting point and high strength and low solubility in aluminum at the elevated temperature so that the constituents resist deformation during the machining operation. The free machining aluminum alloy can be formed as a workpiece and subjected to any machining operation.

Claims

1. A method of machining a free machining aluminum alloy having a free machining constituent:

a) providing a molten aluminum alloy and making it a free machining aluminum alloy by adding between about 0.1% and 2.0% by volume of at least one free machining constituent as a high melting point material to the molten aluminum alloy improve metal removal from the article during machining;

b) forming a free machining aluminum alloy article; and

c) machining the free machining aluminum alloy article into a machines shape while forming finely divided machining debris.

2. The method of claim 1, comprising adding between about 0.3 and 1.5% by volume of the free machining element to the molten aluminum alloy.

3. The method of claim 2, comprising adding between about 0.4 and 1.0% by volume of the free machining element to the molten aluminum alloy.

4. The method of claim 1, wherein the aluminum alloy is an AA2000 series alloy or an AA6000 series alloy.

5. The method of claim 1, wherein the high melting point material is:

a) an oxide selected from the group consisting of aluminum, silicon oxide, titanium oxide, beryllium oxide, chromium oxide, thallium oxide, zirconium oxide, a rare earth oxide, magnesium oxide, iron oxide, nickel oxide, tantalum oxide, tungsten oxide, vanadium oxide, and combinations thereof;

b) a carbide selected from the group consisting of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide, iron carbide, silicon carbide, boron carbide and combinations thereof;

c) a nitride selected from the group consisting of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, tantalum nitride, niobium nitride, chromium nitride, iron nitride, silicon nitride, boron nitride, and combinations thereof;

d) a boride selected from the group consisting of titanium boride, zirconium boride, hafnium boride, vanadium boride, niobium boride, tantalum boride, chromium boride, molybdenum boride, tungsten boride, and combinations thereof;

or

e) a silicide selected from the group consisting of titanium silicide, vanadium silicide, niobium silicide, tantalum silicide, chromium silicide, molybdenum silicide, tungsten silicide, and combinations thereof.

6. The method of claim 1, wherein the forming step comprises casting the molten aluminum alloy.