KR102611753B1 - 7xx-based alloy parts for defense applications with improved explosion resistance - Google Patents

Abstract

The present application relates to armored components made of high-strength aluminum, such as 7xxx series aluminum alloys, which can be used in civilian or military ballistic protection systems. More specifically, the present disclosure relates to armor components, such as add-on increased armor for vehicles and armored shell walls, etc.

Description

7xx-based alloy parts for defense applications with improved explosion resistance

Cross-reference to related applications

This application is an international application claiming priority to U.S. Ser. No. 62/215,842 (filed September 9, 2015), the contents of which are incorporated herein by reference in their entirety.

The present application relates to armored components made of high-strength aluminum, such as 7xxx series aluminum alloys, which can be used in civilian or military ballistic protection systems. More specifically, the present disclosure relates to armor components, such as add-on increased armor for vehicles and armored shell walls, etc.

Increasingly, structures and vehicles are being designed to protect occupants from projectile penetration. These projectiles are typically metal and may attempt to strike structures at high speeds, pierce them, and harm occupants. The purpose of the armored shield is to neutralize the trajectory of such projectiles or fragments.

The demand for ballistic grade aluminum has increased significantly due to the ballistic advantages of low density metals when used as the primary armor of vehicles. Aluminum armor allows for a lightweight shield suitable for the weight requirements of the above-mentioned vehicles.

The armor panels have front and back surfaces that are exposed to impacts and impacts. An armor-piercing projectile can be completely stopped by an armor panel when it impacts such an armor panel. However, some fragments can be violently ejected from the rear of the armor panel and reach the interior of the vehicle.

In order to be characterized by shielding effectiveness, the performance of armored panels must comply with various requirements. Key requirements include that ballistic grade aluminum alloys must achieve a high level of combination of armor penetration (AP) resistance, fragmentation simulated projectile (FSP) resistance as well as blast resistance.

AP resistance means achieving a certain armor-piercing V50 ballistic limit using penetrating projectiles, so-called AP bullets. It is characterized by resistance to puncture. FSP resistance means achieving a given V50 ballistic limit using a different type of projectile: an FSP projectile, the so-called FSP bullet, as specified in the MIL-DTL-46593B standard. FSP resistance is characterized by the ability to withstand impacts that generate fragments. The V50 ballistic limit with velocity dimensions is specified in the MIL-STD-662F (1997) standard. The V50 ballistic limit should be calculated by taking the arithmetic average of the same number of highest partial penetration impact velocities and lowest full penetration impact velocities. The specific V50 required at a given thickness, the amount of individual FSP testing included in calculating the V50, and other material requirements may vary depending on the aluminum alloy. As an example, MIL-DTL-46027K lists requirements for 5083, 5456, and 5059 aluminum alloys.

Blast resistance as specified in MIL-STD-662F (1997) means that, during ballistic tests performed in accordance with this standard, there is no substantial separation or delamination of layers of material, either on the front or back of the armor, in the area around the impact location. It means that it does not occur. These pass-fail criteria for blast and the associated high-low impact velocity averaging method used to evaluate V50 facilitate the test method, but do not allow for further analysis of the amount of blast damage. Additionally, the above-described testing methods may require significantly larger scales of metal, which may hinder the ability to rapidly prototype or sweep across a variety of alloy chemistries, deformation paths, tempering options, etc. Accordingly, herein a burst resistance score is used to quantify burst resistance. Blast resistance scores are investigated using the FSP test according to the MIL-STD-662F (1997) standard. Experiments are performed using 20 mm FSP bullets conforming to MIL-DTL-46593B. The dimensions of the FSP bullet are as follows:

- Diameter: 20 mm - 0.787 inches;

- Length: 23.0 mm - 0.9 inches;

- Flat: 9.3 mm - 0.366 inches.

The burst resistance score is determined by the following method. As shown in Figure 1, at the rear, around the impact location (b), there is a visibly affected area due to the ballistic impact and by the FSP bullet partially penetrating or completely penetrating the plate. There is a range of materials. The boundary of this affected area is indicated by the dotted line a in Figure 1. Included within the deformed area are any areas of exfoliated material or any plugs of material, along with any possible exit holes of the FSP bullet. This area also contains any raised or ruptured material that is still connected to the test plate. Measure the length c, which represents the longest distance from the impact location to the edge or boundary of the deformed area, in a radial direction perpendicular to the direction of impact (i.e. along the back). This maximum length c is multiplied by 2 and from the newly calculated value, 20 mm, corresponding to the diameter of the FSP bullet, is subtracted. To obtain a dimensionless parameter, the so-called burst resistance score, the remaining total is divided by 20 mm. When only the plug is formed, the blast resistance score is 0 and the impact has no significant effect on the neighboring material. Higher scores indicate multiples of the diameter of the impacting bullet. A good score is as low as possible.

Achieving high AP resistance as well as high FSP resistance is still difficult. US Provisional Application No. 61/948,870, the entire contents of which are incorporated herein by reference, discloses armor parts made from 7xxx aluminum-based alloys with an improved combination of AP and FSP resistance. The aluminum alloy disclosed herein essentially:

- 8.4% by weight ≤ Zn ≤ 10.5% by weight;

- 1.3% by weight ≤ Mg ≤ 2% by weight;

- 1.2% by weight ≤ Cu ≤ 2% by weight;

- at least one dispersoid forming element, with a total content of dispersoid forming elements greater than 0.05% by weight;

- Consists substantially of aluminum, the remainder being minor elements and impurities.

According to US 61/948,870, the armored parts are in the form of plates with a thickness ranging from about 0.5 inches to about 3 inches; Aged to achieve high AP and FSP V50 ballistic limits. That is, the FSP V50 ballistic limits are:

V50 (FSP 20 ㎜) > 1633T ² - 1479T + 1290,

Where T is the thickness of the plate in inches and the unit of V50 is feet/s. “FSP 20 mm” refers to FSP experiments performed using 20 mm diameter bullets.

AP V50 ballistic limits are:

V50 (0.3cal AP ㎜) > -282T ² - 1850T + 610,

Where T is the thickness of the plate in inches and the unit of V50 is feet/s. “0.3cal AP V50” refers to AP experiments conducted using 0.30 caliber bullets.

The combined target ballistic properties can be obtained through multiple stages of aging during the manufacturing process. Normal aging treatment is aged at about 110°C to 130°C for about 4 to 8 hours, followed by aging at about 140°C to 160°C for about 12 to 20 hours.

Usually, in addition to FSP and AP ballistic resistance, high blast resistance is also required. The present invention provides an armored component with high AP and FSP ballistic resistance as well as improved blast resistance.

The 7xxx series aluminum alloy armor parts manufactured according to the present invention exhibit improved spalling resistance. The alloy composition as well as processing parameters are adjusted to increase blast resistance and to have high AP and FSP ballistic resistance.

Preferably, the composition of the 7xxx series aluminum alloy is selected to include Zr as at least one dispersoid forming element, more preferably from about 0.04% to about 0.15% by weight of Zr.

1 depicts one embodiment of a method used to determine a burst resistance score in accordance with the present disclosure.

Unless otherwise stated, all composition proportions are expressed as weight percent (% by weight) based on the total weight of the alloy. The names of the alloys follow the rules of the Aluminum Association, known to those skilled in the art.

As used herein, when referring to an amount of an element, the expression “up to” means that the composition of the element is optional and includes zero (0) amount of the element. When the term “between” appears in this application and claims, it is understood that the number of upper and lower limits of the range is included. Similarly, "lower than" or "higher than" and such phrases include numbers within the recited range.

The present invention provides a method for manufacturing armor parts:

a) casting a 7xxx series aluminum alloy to obtain an ingot, wherein the alloy is essentially

- 8.4% by weight ≤ Zn ≤ 10.5% by weight;

- 1.3% by weight ≤ Mg ≤ 2% by weight;

- 1.2% by weight ≤ Cu ≤ 2% by weight;

- at least one dispersoid forming element, with a total content of dispersoid forming elements of at least 0.04% by weight;

- the balance substantially comprising aluminum, incidental elements and impurities;

A casting step consisting of;

b) homogenizing the ingot;

c) a hot working step of hot working the homogenized ingot to obtain a plate with a first thickness (T ₁ );

d) cold working the plate with said first thickness to obtain a plate with a second thickness (T ₂ ), wherein T ₂ = T ₁ - (x ₁ *T ₂ )/100, and 0.5 ≤ x A cold working step wherein ₁ ≤ 15;

e) solution heat treatment step;

f) quenching step; and

g) relates to a method comprising an aging step.

Alloy products according to the invention can be prepared using conventional melting processes and by casting into ingot form. During casting, grain refiners described below may be added. After scalping and homogenization at 460°C to 520°C for 5 to 60 hours, the ingot is also hot worked, usually in several stages, to obtain a plate with a first thickness T ₁ . According to one embodiment, the hot working is hot rolling or forging, more preferably hot rolling.

It has been found that burst resistance is improved by performing a cold working step prior to solution heat treatment (SHT), and more specifically between the hot working step and the solution heat treatment. After the cold working step, the cold worked plate has a second thickness T ₂ , where T ₂ = T ₁ - (x ₁ *T ₂ )/100 and 0.5 ≤ x ₁ ≤ 15. According to one embodiment, the cold worked plate has a second thickness T ₂ , where T ₂ = T ₁ - (x ₁ *T ₂ )/100 and 2 ≤ x ₁ ≤ 10, preferably is 4 ≤ x ₁ ≤ 8. According to one embodiment, the cold working step prior to solution heat treatment is a cold rolling step.

Afterwards, the cold worked plate with the second thickness T ₂ is solution heat treated and quenched. In a preferred embodiment, the solution heat treatment is performed at 460°C to 480°C for 1 to 5 hours and quenched to a temperature typically lower than 95°C.

Optionally, after SHT and quenching, another cold working step is performed to obtain a plate with a third thickness T ₃ . This other cold working step may be stretching. The other cold working steps cause plastic deformation, for example up to 3%, typically between 1% and 3%. If a second cold working step is not applied, the second thickness T ₂ is the final thickness of the armor part. If the method according to the invention involves two cold working steps, the final thickness is the third thickness of the plate (T 3 ) obtained after the second cold working step, and the final thickness of the armor part is the second thickness (T ₃ ). It is smaller than T ₂ ).

According to one embodiment, step g) comprises at least two stages of aging. Preferably, the two stages of aging are:

- a first aging step conducted at about 110°C to 130°C, more preferably at about 115°C to 125°C for about 4 to 8 hours, more preferably 5 to 7 hours; and

- a second aging step at about 130°C to 180°C, more preferably at about 145°C to 165°C, for about 12 to 20 hours, more preferably 14 to 18 hours.

According to another embodiment, aging is performed such that the total equivalent time at 150°C is from about 5 hours to about 50 hours, more preferably from about 10 hours to about 40 hours. The total equivalent time t(eq) at 150°C is given by the equation:

here:

- T is the instantaneous temperature of the treatment (in Kelvin);

- t represents the time including the heating and cooling steps;

- T _ref is the reference temperature, its value is 423 K (i.e. 150° C.);

- t(eq) is expressed in units of time;

- 15683 is the temperature derived from the diffusion activation energy of Mg (Q = 130400 J/mol).

In particular, according to the above-described embodiments, the aging step is considered to improve both AP and FSP resistance.

According to a preferred embodiment, the provided armor parts are plates with a final thickness ranging from 0.5 inches to 3 inches.

The alloy contains zinc (Zn), copper (Cu) and magnesium (Mg) as main alloying elements, at least one dispersoid forming enzyme with a total content of 0.04% by weight or more as a dispersoid forming element, and substantially aluminum, The remainder, including incidental elements and impurities, generally comprises and in some cases consists essentially of.

The Zn content ranges from about 8.4% to about 10.5% by weight, preferably from about 8.5% to about 9.5% by weight, and more preferably from about 8.5% to about 9% by weight. Experiments have shown that the above-mentioned dosages give the best results in both AP and FSP ballistic tests and/or improve blast resistance scores.

The magnesium content ranges from about 1.3% to about 2% by weight, preferably from about 1.5% to about 2% by weight, and more preferably from about 1.6% to about 1.9% by weight.

In a preferred embodiment, the Mg/Zn ratio is less than or equal to 0.25, more preferably less than or equal to 0.20, where Mg and Zn represent weight percent of magnesium and zinc, respectively.

The copper content ranges from about 1.2% to about 2% by weight. Preferably, the Cu content is 1.5% to 1.9% by weight. When the copper and magnesium contents were approximately equal, typically 0.9 ≤ Cu/Mg ≤ 1.1, high AP and FSP resistances were obtained.

At least one dispersoid forming element such as Zr, Sc, V, Hf, Ti, Cr and Mn is added. As used herein, dispersoid forming element refers to an element intentionally added to control grain structure. The total content of dispersoid forming elements is at least 0.04% by weight, preferably about 0.04% to about 0.3% by weight. The optimal level of dispersoid forming elements depends on the processing. If scandium is added, its content is preferably less than about 0.3% by weight, and more preferably less than 0.17% by weight. When combined with Zr, it is preferred that the sum of Sc and Zr is less than about 0.17 weight percent. The alloy may also contain Cr, Hf and V in amounts of less than 0.3% by weight and preferably less than 0.15% by weight. When Mn is added, its content is preferably less than 0.3% by weight.

In a preferred embodiment, the dispersoid forming element is essentially zirconium. Preferably, the Zr content is less than about 0.15% by weight, more preferably 0.04% to 0.1% by weight, and even more preferably 0.05% to 0.08% by weight. The best AP and FSP resistances are a compromise and/or the best burst resistance scores are observed for 0.05 wt% ≤ Zr ≤ 0.08 wt%. The inventors herein have found that, compared to the 7xxx alloy series described in US 61/948,870, by not only lowering the Zr content but also introducing cold working before SHT, the spalling resistance is improved and the compromise between AP and FSP is maintained at a high level. Became,

(i) V50 (FSP 20 mm) > 1633T ² - 1479T + 1290 (where T is the thickness of the plate (unit: inches) and the unit of V50 is feet/s); and

(ii) It was found that V50 (0.30cal AP M2) > -282T ² - 1850T + 610 (where T is the thickness of the plate (unit: inch) and the unit of V50 is feet/s).

By making the Zr content as described above, as well as performing cold working before SHT and quenching, it is believed that not only the grain size is increased but also the equiaxed grain shape is increased.

As used herein, an impurity refers to an element that may be found in trace amounts in an alloy but is not intentionally added to the alloy. These elements arise due to natural impurities within the individual alloy elements or due to the manufacturing process. Fe and Si are generally the main impurities present in aluminum alloys. The Fe content is preferably less than 0.3% by weight, and more preferably less than 0.1% by weight. The Si content is preferably less than 0.2% by weight, and more preferably less than 0.1% by weight. Preferably, each of the other impurity elements is present such that the content taken as weight percent based on the total weight of the alloy is less than or equal to about 0.05 weight percent, and the total impurity content (other than Fe or Si) is less than or equal to about 0.15 weight percent. do.

As used herein, accessory element refers to an element that may be optionally added to the alloy during the manufacturing process. The addition of these elements results from casting aids and deoxidizers. Titanium, titanium boride (TiB ₂ ), or titanium carbide (TiC) are common grain growth inhibitors. Deoxidants may include Ca, Sr, and Be. Preferably, the amount of minor elements Ca, Sr, Be, Br and C is less than 0.005% by weight and the amount of Ti is less than 0.05% by weight.

In a preferred embodiment, the chemical composition of the alloy is:

- 8.5% by weight ≤ Zn ≤ 9.5% by weight;

- 1.5% by weight ≤ Mg ≤ 2% by weight;

- 1.5% by weight ≤ Cu ≤ 1.9% by weight;

- 0.04% by weight ≤ Zr ≤ 0.10% by weight, preferably 0.05% by weight ≤ Zr ≤ 0.08% by weight;

- 0.15% by weight or less of dispersoid forming elements other than Zr;

- The balance substantially includes aluminum, incidental elements and impurities.

Another aspect of the invention is an armor component made from a 7xxx series aluminum alloy, said alloy having essentially:

- 8.4% by weight ≤ Zn ≤ 10.5% by weight;

- 1.3% by weight ≤ Mg ≤ 2% by weight;

- 1.2% by weight ≤ Cu ≤ 2% by weight;

- at least one dispersoid forming element, with a total content of dispersoid forming elements of at least 0.04% by weight;

- the balance substantially comprising aluminum, incidental elements and impurities;

It consists of;

The 7xxx series aluminum alloys are cold worked prior to solution heat treatment to achieve improved spalling resistance compared to armor parts obtained with the same manufacturing process, except that they do not include a cold working step prior to solution heat treatment. is reduced by 0.5% to 15% (0.5 ≤ x1 ≤ 15, as previously defined) and is in the form of a plate having a final thickness of about 0.5 inches to about 3 inches.

Example

Example One: explosion resistance

Alloy plate products were prepared from alloys having the chemical compositions in weight percent shown in Table 1.

Table 1: Composition of plate product (% by weight)

Plate products were manufactured using the following process:

- casting an ingot of an alloy having the composition shown in Table 1;

- Homogenizing the ingot;

- hot working the homogenized ingot to reach the intermediate dimension (T ₁ );

- For plate products B-3 and B-4 only, the ingot of the intermediate dimension (T ₁ ) is cold worked to reach the final dimension (T ₂ ), so that the thickness of the ingot of the intermediate dimension (T ₁ ) is 2.9 respectively. % and 6.3% reduction steps;

- solution heat treatment of the plate;

- Quenching stage;

- for plate product A only, stretching the plate to obtain a plastic strain of about 2%;

- Artificially aging the plate.

All sample plates were aged during the two-stage process. Sample A was aged at 120°C for 24 hours (first step), followed by 35 hours at 150°C (second step). Samples B-1, B-2, B-3 and B-4 were aged at 120°C for 6 hours (first step), followed by 160°C for 16 hours (second step).

Table 2: Experimental results

The final thickness of each plate product ranges from 1.25 inches to 1.37 inches. As can be seen from the third column of Table 2, samples A, B-1 and B-2 did not undergo cold working prior to SHT, whereas samples B-3 and B-4 underwent cold rolling prior to SHT. Thus, the thickness of the so-called intermediate sample plate was reduced by 2.9% and 6.3%, respectively. In the third column of Table 2, the values given for samples B-3 and B-4 represent the value x ₁ such that T ₂ = T ₁ - (x ₁ *T ₂ )/100.

Samples B-3 and B-4 have a low Zr content within the desired range as well as a cold working step prior to solution heat treatment and quenching.

For all plate products, burst resistance was investigated using the FSP test according to the MIL-STD-662F (1997) standard. Experiments were performed using 20 mm FSP bullets conforming to MIL-DTL-46593B. The dimensions of the FSP bullet are as follows:

- Diameter: 20 mm - 0.787 inches;

- Length: 23.0 mm - 0.9 inches;

- Flat: 9.3 mm - 0.366 inches.

The fourth column of Table 2 shows the blast resistance scores. This score is determined by the following method. As shown in Figure 1, at the rear, around the impact location (b), there is a visibly affected area due to the ballistic hit and by the FSP bullet partially penetrating or completely penetrating the plate. There is a realm of materials. The boundary of this affected area is indicated by the dotted line a in Figure 1. Included within the deformed area are any areas of exfoliated material or any plugs of material, along with any possible exit holes of the FSP bullet. This area also contains any raised or ruptured material that is still connected to the test plate. Measure the length c, which represents the longest distance from the impact location to the edge or boundary of the deformed area, in a radial direction perpendicular to the direction of impact (i.e. along the back). Multiply this maximum length c by 2 and subtract 20 mm, corresponding to the diameter of the FSP bullet, from the newly calculated value. To obtain a dimensionless parameter, the so-called burst resistance score, the remaining total is divided by 20 mm. When only the plug is formed, the blast resistance score is 0 and the impact has no significant effect on the neighboring material. Higher scores indicate multiples of the diameter of the impacting bullet. A good score is as low as possible.

The fifth column of Table 2 shows the measured projectile velocity when performing the FSP test.

From these results, the following conclusions can be drawn:

- Plate products B-3 and B-4 show better detonation resistance than plate products B-1 and B-2;

- Plate product B-4 exhibits superior detonation resistance than plate product B-3.

This tends to show that the cold working step prior to SHT results in an improvement in burst resistance. Additionally, by combining the cold working described above with a low content of Zr, the blast resistance score can be significantly improved and, as evaluated in Example 2, high resistance can be maintained against both AP and FSP bullets.

Example 2: AP and FSP characteristic

Alloy plate products were prepared from alloys having the chemical compositions in weight percent shown in Table 3.

Table 3: Composition of sample plate of Example 2 (% by weight)

Alloys C, D and E have chemical compositions according to the invention.

Plate products were manufactured using the following process according to the invention:

- casting an ingot of an alloy having the composition shown in Table 3;

- Homogenizing the ingot;

- hot working the homogenized ingot to reach the intermediate dimension (T ₁ );

- cold working the ingot of the intermediate dimension (T ₁ ) to reach the final dimension (T ₂ ), thereby reducing the thickness of the ingot of the intermediate dimension (T ₁ ) by 2.9% (x ₁ = 2.9);

- solution heat treatment of the plate;

- Quenching stage;

- stretching the plate to obtain a plastic strain of 2% to 3%;

- Artificially aging the stretched plate at 120°C for 6 hours, followed by artificially aging at 160°C for 16 hours.

The plate products had different thicknesses ranging from 1.0" to 1.6" and were tested for their ballistic properties. Two ballistic tests were conducted according to the U.S. military standard MIL-STD-662F (1997): an armor penetration test using a 0.3 inch (7.62 mm) projectile and an FSP test using a 20 mm fragment simulation projectile. Table 4 lists the results of AP and FSP, with the minimum required ballistic limits specified in US Military Specification MIL-DTL 32375 [V50 (0.3 Cal AP M2) 7085 requirements respectively: MIL-DTL-32375 (MR) Appendix A, 19 -Page 20, "Required BL(P) - Type B" and V50 (FSP 20 mm) 7085 Requirements: MIL-DTL-32375 (MR) Appendix A, page 18, "Required BL(P) - Type B"] Compare with This specification covers 7085 forged aluminum alloy armor plates for non-melt welded applications with nominal thicknesses from 0.500 inches to 3,000 inches and specifies plate thicknesses as well as minimum required ballistic limits for various types of projectiles.

Table 4: Experimental results of Example 2

Plate products C, D and E combine high AP performance and high FSP performance. In particular, all of the aforementioned plate products meet the minimum required ballistic limits set for alloy 7085 in U.S. Military Specification MIL-DTL 32375. Additionally, for Examples 1 and 2, by combining cold working prior to SHT with a low Zr content, i.e., Zr ≤ 0.08 wt%, the blast resistance score is significantly improved, while maintaining high resistance to both AP and FSP bullets. It seems to work.

Claims (16)

A method of manufacturing armored parts having a final thickness ranging from 0.5 inches to 3 inches, comprising:
a) Casting a 7xxx series aluminum alloy to obtain an ingot, wherein the alloy is basically
- 8.4% by weight ≤ Zn ≤ 10.5% by weight;
- 1.3% by weight ≤ Mg ≤ 2% by weight;
- 1.2% by weight ≤ Cu ≤ 2% by weight;
- 0.04% by weight ≤ Zr ≤ 0.08% by weight;
- The remainder including aluminum, incidental elements and impurities.
A casting step consisting of or including these;
b) homogenizing the ingot;
c) a hot working step of hot working the homogenized ingot to obtain a plate with a first thickness (T ₁ );
d) cold working the plate with said first thickness to obtain a plate with a second thickness (T ₂ ), wherein T ₂ = T ₁ - (x ₁ *T ₂ )/100, and 0.5 ≤ x A cold working step wherein ₁ ≤ 15;
e) solution heat treatment step;
f) quenching step; and
g) Aging stage
How to include . The method of claim 1, wherein 2 ≤ x ₁ ≤ 10. The method of claim 1, wherein the cold working step d) is a cold rolling step. 2. The method of claim 1, wherein step g) aging comprises at least two stages of aging. The method of claim 4, wherein the two stages of prescription are:
- First aging conducted at 110°C to 130°C for 4 to 8 hours; and
- Second aging at 130°C to 180°C for 12 to 20 hours
A method comprising: The method of claim 1, wherein the aging step g) is performed such that the total equivalent time at 150° C. is 5 hours to 50 hours. The method of claim 1, comprising another cold working step between steps f) and g), cold working to obtain a plate having a third thickness (T ₃ ). 8. The method of claim 7, wherein the cold working step of cold working to obtain a plate having a third thickness (T ₃ ) causes plastic deformation in the range of 1% to 3%. 8. The method of claim 7, wherein the cold working step of cold working to obtain a plate having a third thickness (T ₃ ) consists of or includes stretching. An armored part manufactured from a 7xxx series aluminum alloy, comprising:
The alloy is basically:
- 8.4% by weight ≤ Zn ≤ 10.5% by weight;
- 1.3% by weight ≤ Mg ≤ 2% by weight;
- 1.2% by weight ≤ Cu ≤ 2% by weight;
- 0.04% by weight ≤ Zr ≤ 0.08% by weight;
- the remainder including aluminum, incidental elements and impurities;
consists of or includes these;
The 7xxx series aluminum alloy is in the form of a plate having a final thickness of 0.5 inches to 3 inches,
The 7xxx series aluminum alloy is,
a) casting the 7xxx series aluminum alloy to obtain an ingot;
b) homogenizing the ingot;
c) a hot working step of hot working the homogenized ingot to obtain a plate with a first thickness (T ₁ );
d) cold working the plate with said first thickness to obtain a plate with a second thickness (T ₂ ), wherein T ₂ = T ₁ - (x ₁ *T ₂ )/100, and 0.5 ≤ x a cold working step wherein ₁ ≤ 15;
e) solution heat treatment step;
f) quenching step; and
g) Aging stage
An armored part manufactured by, wherein improved spalling resistance is achieved compared to an armored part obtained by the same manufacturing process, except that it does not include a cold working step prior to the solution heat treatment step. delete delete delete delete delete delete