US-12624422-B2 - Aluminum alloy forging and manufacturing method thereof

US12624422B2US 12624422 B2US12624422 B2US 12624422B2US-12624422-B2

Abstract

An aluminum alloy forging formed of an aluminum alloy containing Cu: 0.15% to 1.0%, Mg: 0.6% to 1.35%, Si: 0.95% to 1.45%, Mn: 0.4% to 0.6%, Fe: 0.2% to 0.7%, Cr: 0.05% to 0.35%, Ti: 0.012% to 0.035%, B: 0.0001% to 0.03%, Zn: 0.25% or less, Zr: 0.05% or less (all % given by mass), and a remainder consisting of Al and inevitable impurities, in which a crystal grain diameter where a maximum principal stress is applied is 20 to 40 μm. The aluminum alloy forging has a structure in which an average shortest distance from a precipitate having a major axis of 0.1 μm or more to a crystal grain boundary in a cross-sectional structure with a visual field area of 8,000 μm 2 is in a range of 0.1 μm to 2.0 μm, and a fatigue life at a load stress of 150 MPa is 6×10 6 .

Inventors

Takuya ARAYAMA
Hiroaki Murakami
Yoshifumi Kimura

Assignees

RESONAC CORPORATION

Dates

Publication Date: 20260512
Application Date: 20221208
Priority Date: 20220118

Claims (1)

1 . A method for manufacturing an aluminum alloy forging, comprising: a molten metal forming step of preparing a molten alloy; a casting step of casting the molten alloy at a cooling speed of 100 to 140° C./sec during casting to obtain a cast aluminum alloy rod; and a homogenization heat treatment step of subjecting the cast aluminum alloy rod obtained in the casting step to a homogenization heat treatment at a temperature of 370° C. or higher and 470° C. or lower for 4 to 10 hours so that a crystal grain diameter is 110 μm or less in a metallographic structure of an obtained cast rod, wherein the molten alloy comprises: Cu: 0.15% by mass to 1.0% by mass; Mg: 0.6% by mass to 1.35% by mass; Si: 0.95% by mass to 1.45% by mass; Mn: 0.4% by mass to 0.6% by mass; Fe: 0.2% by mass to 0.7% by mass; Cr: 0.05% by mass to 0.35% by mass; Ti: 0.012% by mass to 0.035% by mass; B: 0.0001% by mass to 0.03% by mass; Zn: 0.25% by mass or less; Zr: 0.05% by mass or less; and a remainder consisting of Al and inevitable impurities, a crystal grain diameter in a part of the aluminum alloy forging where a maximum principal stress is applied to the part is 20 to 40 μm, the manufactured aluminum alloy forging has a structure in which an average shortest distance from a precipitate having a major axis of 0.1 μm or more to a crystal grain boundary in a cross-sectional structure with a visual field area of 8,000 μm 2 is in a range of 0.1 μm or more and 2.0 μm or less, and the manufactured aluminum alloy forging has fatigue characteristics in which a fatigue life at a load stress of 150 MPa is 6×10 6 or more at room temperature.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a National Stage of International Application No. PCT/JP2022/045362 filed Dec. 8, 2022, claiming priority based on Japanese Patent Application No. 2022-005676 filed Jan. 18, 2022, the respective contents of which are incorporated herein by reference in their entireties. TECHNICAL FIELD The present invention relates to an aluminum alloy forging and a manufacturing method thereof. BACKGROUND ART In recent years, aluminum alloys have had wide applications as structural members of various products due to their lightness. For example, for automobile suspension and bumper parts, high-tensile strength steel has been used. Meanwhile, high-strength aluminum alloy materials have been used in recent years. In addition, iron-based materials have been exclusively used for auto parts, especially suspension parts. Meanwhile, in recent years, the iron-based materials have been replaced by aluminum materials or aluminum alloy materials in many cases with primary purpose of weight reduction. Since these auto parts require excellent corrosion resistance, high strength, and excellent workability, Al—Mg—Si-based alloys, especially A6061, are frequently used as aluminum alloy materials. In order to improve the strength, such auto parts are manufactured by forging, which is one type of plastic working, using an aluminum alloy material as a working material. In addition, recently, suspension parts obtained by forging a cast member as a raw material without extruding and then subjecting it to a solutionizing treatment and an artificial aging treatment (T6 treatment) have started to be put to practical use due to the need to reduce costs, and development of high-strength alloys which will replace A6061 of the related art has continued in order to further reduce the weight (For example, see Patent Documents 1 to 3). CITATION LIST Patent Documents [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. H5-059477 [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. H5-247574 [Patent Document 3] Japanese Unexamined Patent Application, First Publication No. H6-256880 SUMMARY OF INVENTION Technical Problem In recent years, from the viewpoint of reducing CO2 emissions, there has been demand for lighter automobiles, and demand for aluminum is on the rise. However, a substitute for ferrous materials is required to be further increased in strength. Meanwhile, as one method for increasing the strength, suppressing the formation of a recrystallized structure and refining crystal grain diameters in plastic working and a solutionizing treatment step have been known. However, the Al—Mg—Si-based high-strength alloys described above have a problem in that it is not possible to obtain a sufficiently high strength due to the recrystallization of the worked structure and the generation of coarse crystal grains in the forging and heat treatment step. Therefore, in order to prevent the formation of coarse recrystallized grains, Zr is added to prevent recrystallization (for example, see Patent Documents 1 and 2). However, the addition of Zr is effective in preventing recrystallization, but has the following problems. (1) Due to the addition of Zr, the crystal grain refining effect of an Al—Ti—B-based alloy is reduced, and the crystal grains of an ingot itself are made coarse. This leads to a reduction in strength of a worked product (forging) after plastic working.(2) Since the crystal grain refining effect of the ingot itself is reduced, ingot cracks are likely to occur, internal defects increase, and the yield deteriorates.(3) Zr forms compounds with an Al—Ti—B-based alloy, and the compounds are deposited on a bottom of a furnace where a molten alloy is stored, and contaminates the furnace. The compounds are coarsely crystallized also in a manufactured ingot, and cause a reduction in strength. As described above, the addition of Zr is effective in preventing recrystallization, but it has been difficult to maintain strength stability. One aspect of the present invention is contrived in view of such technical background, and one object thereof is to provide an aluminum alloy forging having excellent fatigue characteristics at room temperature and a manufacturing method thereof. Solution to Problem One aspect of the present invention provides the following means in order to solve the problems. (1) An aluminum alloy forging formed of an aluminum alloy containing: Cu: 0.15% by mass to 1.0% by mass;Mg: 0.6% by mass to 1.35% by mass;Si: 0.95% by mass to 1.45% by mass;Mn: 0.4% by mass to 0.6% by mass;Fe: 0.2% by mass to 0.7% by mass;Cr: 0.05% by mass to 0.35% by mass;Ti: 0.012% by mass to 0.035% by mass;B: 0.0001% by mass to 0.03% by mass;Zn: 0.25% by mass or less;Zr: 0.05% by mass or less; anda remainder consisting of Al and inevitable impurities, in which a crystal grain diameter in a part of the aluminum alloy forging where a m