Al-zn-cu-mg alloys and their manufacturing process

a technology of aluminum base alloys and manufacturing processes, applied in manufacturing tools, furnaces, heat treatment equipment, etc., can solve the problems of difficult to take into account design parts, consider detrimental, and consider crack deviation, so as to improve the growth rate of fatigue cracks and increase the tendency of crack deviation

Pending Publication Date: 2022-03-17
CONSTELLIUM ISSOIRE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0022]An object of the invention was to provide an Al—Zn—Cu—Mg alloy having a specific composition range and manufacturing process that enables, for thick rolled products, an improved fatigue crack growth rate without increased tendency of crack deviation.

Problems solved by technology

Crack deviation happens on a microscopic scale (1 mm) but it is considered detrimental only if the crack direction remains stable after deviation (macroscopic scale).
Crack deviation has been considered as a major problem by aircraft manufacturers because it is difficult to take into account to design parts, using traditional design methods.
This is because crack deviation invalidates conventional, mode I based, materials testing procedure and design models.
The crack deviation problem has proven difficult to solve.
However crack deviation improvement is often related to higher fatigue crack growth rate in the original cracking plane, before deviation.
Again, such three step aging is long and difficult to master.

Method used

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  • Al-zn-cu-mg alloys and their manufacturing process
  • Al-zn-cu-mg alloys and their manufacturing process
  • Al-zn-cu-mg alloys and their manufacturing process

Examples

Experimental program
Comparison scheme
Effect test

example

Example 1

[0083]Two ingots were cast, one of a product according to the invention (A), and one reference example (B) with the following composition (Table 1):

TABLE 1composition (wt. %) of a cast accordingto the invention and a reference cast.AlloySiFeCuMgZnTiZrA0.030.042.131.757.050.040.06B0.050.091.642.256.100.020.11

[0084]The ingots were then scalped and homogenized at about 475° C. The ingots were hot rolled to a plate of thickness of 102 mm (alloy A) or 110 mm (alloys B). Hot rolling entry temperature was 350° C. for alloy A and 440° C. for alloy B. The plates were solution heat treated with a soak temperature of about 475° C. The plates were quenched and stretched with a permanent elongation comprised between 2.0 and 2.5%.

[0085]The reference plates were submitted to a two-step aging of 4 hours at 120° C. followed by approximately 15 hours at 155° C. for a total equivalent time at 155° C. of 17 hours, to obtain a T7651 temper.

[0086]The plates made of alloy A had at mid-thickness m...

example 2

[0095]One additional ingot was cast, with a composition according to the invention (C), (Table 6):

TABLE 6composition (wt. %) of cast C.AlloySiFeCuMgZnTiZrC0.030.042.151.657.110.030.10

[0096]The ingot was then scalped and homogenized at 475° C. The ingot was hot rolled to a plate of thickness of 152 mm Hot rolling entry temperature was 420° C. The plate was solution heat treated with a soak temperature of 475° C. The plate was quenched and stretched with a permanent elongation comprised between 2.0 and 2.5%.

[0097]Due to the high hot rolling temperature, the plate microstructure was not according to the invention, the plate made had at mid-thickness less than 20% of recrystallized grains.

[0098]The L-S fatigue crack growth rate was measured according to standard ASTM E647 at mid-thickness and quarter thickness in the L-S direction on CT specimen (CT10W40 thickness 10 mm, width 40 mm) under a maximum load of 4 KN and R=0.1. The results are presented in Table 7.

TABLE 7Results of the L-S f...

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Abstract

The invention relates to a rolled aluminum-based alloy product having a thickness of at least 80 mm comprising, (in weight %): Zn 6.85-7.25, Mg 1.55-1.95, Cu 1.90-2.30, Zr 0.04-0.10, Ti 0-0.15, Fe 0-0.15, Si 0-0.15, other elements ≤0.05 each and ≤0.15 total, remainder Al, wherein at mid-thickness more than 75% of grains are recrystallized or at mid-thickness 30 to 75% of grains are recrystallized and non-recrystallized grains have an aspect ratio in a L/ST cross section less than 3. A process for the manufacture of a rolled aluminum-based alloy product comprises the steps of: (a) casting an ingot made in an alloy according to the invention, (b) conducting an homogenization of the ingot (c) conducting hot rolling of said homogenized ingot in one or more stages by rolling, (d) conducting a solution heat treatment a quench, (e) conducting stress relieving, and, (f) conducting an artificial aging treatment. The products of the invention are suitable for aircraft construction and have advantageous fatigue crack growth properties.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to aluminum base alloys and more particularly, Al—Zn—Cu—Mg aluminum base alloys, in particular for aerospace applications.DESCRIPTION OF RELATED ART[0002]Al—Zn—Cu—Mg aluminum base alloys have been used extensively in the aerospace industry for many years. With the evolution of airplane structures and efforts directed towards the goal of reducing both weight and cost, an optimum compromise between properties such as strength, toughness and corrosion resistance is continuously sought. Also, process improvement in casting, rolling and heat treatment can advantageously provide further control in the composition diagram of an alloy and property compromise.[0003]Thick rolled, forged or extruded products made of Al—Zn—Cu—Mg aluminum base alloys are used in particular to produce integrally machined high strength structural parts for the aeronautic industry, for example wing elements such as wing ribs, spars, frames and the ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C21/10C22F1/053C21D9/46
CPCC22C21/10C21D9/46C22F1/053
Inventor NIZERY, EREMBERTWHELCHEL, RICKYEHRSTROM, JEAN-CHRISTOPHE
Owner CONSTELLIUM ISSOIRE
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