A Comprehensive Guide to Aluminum 7050 (UNS A97050)

What is aluminum 7050?

7050 alloy is a kind of Al-Zn-Mg-Cu series wrought aluminum alloy with high strength and heat treatment strengthening, also known as superhard aluminum. It can produce thick plates, pipes, forgings, wires, flanges, pipe fittings, etc., and is not used for rolling thin plates. The main alloying element of 7050 series aluminum alloy is zinc. Adding magnesium to the alloy containing 3 % -7.5 % zinc can form MgZn₂ with a significant strengthening effect, so the alloy’s heat treatment effect is much better than that of Al-Zn binary alloy. Increasing the content of zinc and magnesium in the alloy, the tensile hardness will be further improved, and its ability to resist stress corrosion and exfoliation corrosion will increase. After heat treatment, it can achieve very high strength characteristics. This material series generally adds a small amount of copper chromium and other alloys. In this series, 7050-7451 aluminum alloy is the best product in the aluminum alloy, known as the best product in the aluminum alloy. It has high strength and is far better than soft steel. This alloy has good mechanical properties and anodic reaction.

Characteristics of Aluminum 7050 (UNS A97050)

7050 aluminum alloy is heat-treatable. It has high toughness and high strength. It has high resistance to stress corrosion cracking. Its conductivity is equivalent to 40 % of copper. 7050 aluminum is known as a commercial aerospace alloy.
7050 aluminum alloy has the following properties:

• Good heat treatment dimensional stability: 7050 aluminum alloy has high hardenability, good comprehensive performance below medium temperature, and small heat treatment deformation.
• 7050 aluminum alloy has good machining and wear resistance.
• 7050 is a high-strength heat-treatable alloy with extremely high strength and resistance to exfoliation corrosion and stress corrosion cracking. It is commonly used in aircraft structural parts for medium and thick plate extrusion, free forging, and die forging. The aluminum alloy based on chromium and molybdenum is more suitable for forced cooling by water spraying.
• The commonly used hardness range of 7050 aluminum alloy is 52-54 HRC.

Trade Names of aluminum alloy 7050

UNS A97050, ISO AlZn6CuMgZr, AA7050-T7451, Al7050-T7451, AMS 4108, AMS 4201, ASTM B247, ASTM B316, QQ A-430

Chemical Composition of Aluminum 7050 (UNS A97050)

Element	Content (%)
Aluminum, Al	87.3 – 90.3
Zinc, Z	5.7 – 6.7
Copper, Cu	2.0 – 2.6
Magnesium, Mg	1.9 – 2.6
Zirconium, Zr	0.08 – 0.15
Iron, Fe	≤ 0.15
Silicon, Si	≤ 0.12
Mangnese, Mn	≤ 0.10
Titanium, Ti	≤ 0.06
Chromium, Cr	≤ 0.04

Mechanical Properties of Aluminum 7050 (UNS A97050)

Property	Metric	Imperial
Hardness, Brinell	140	140
Hardness, Knoop	177	177
Hardness, Rockewell A	51.6	51.6
Hardness, Rockwell B	84	84
Hardness, Vickers	162	162
Ultimate Tensile Strength	524 MPa	76000 psi
Tensile Yield Strength	469 MPa	68000 psi
Elongation at Break	0.11	0.11
Modulus of Elasticity	71.6 GPa	10400 ksi
Poisson’s Ratio	0.33	0.33
Shear Modulus	26.9 GPa	3900 ksi
Shear Strength	303 MPa	44000 psi

Physical Properties of aluminum alloy 7050

Property	Metric	Imperial
Density	2.6-2.8 g/cm3	0.0939-0.101 lb/in3
Melting Point	494°C	920°F

Thermal Properties of aluminum alloy 7050

Property	Metric	Imperial
Specific Heat Capacity	0.860 J/g-°C	0.206 BTU/lb-°F
Thermal Conductivity	157 W/m-K	1090 BTU-in/hr-ft²-°F
Solidus	488 °C	910 °F
Liquidus	629.4 °C	1165 °F

Electrical Properties of Aluminum 7050 (UNS A97050)

Component Elements Properties	Original Value
Aluminum, Al	87.3 – 90.3%
Chromium, Cr	≤0.04%
Copper, Cu	2.0 – 2.6%
Iron, Fe	≤0.15%
Magnesium, Mg	1.9 – 2.6%
Manganese, Mn	≤0.10%
Other, each	≤0.05%
Other, total	≤0.15%
Silicon, Si	≤0.12%
Titanium, Ti	≤0.06%
Zinc, Zn	5.7 – 6.7%
Zirconium, Zr	0.08 – 0.15%

Manufacture and heat treatment of aluminum 7050 (UNS A97050)

Forming of aluminum 7050 (UNS A97050)

Al/Al 7050 alloy can be formed under O tempering or heat treatment conditions.

Welding of aluminum 7050 (UNS A97050)

Aluminum/aluminum 7050 alloy should not be welded to prevent cracking and porosity formation. The resulting welded joint will be weaker than the parent metal. Tungsten gas shielded welding or metal gas shielded welding method is not preferred for welding the alloy. Welding of aluminum 7050 requires special care, because this alloy has a higher melting point than other alloys with similar strength characteristics. If improperly operated, it will increase the risk of warpage. However, if proper shielding gas and joint preparation procedures are used for correct welding, standard welding techniques can still be used, such as TIG welding or MIG welding to start the welding process itself.

Heat treatment of aluminum 7050 (UNS A97050)

Aluminum 7050 can be heat-treated by cold working or solid solution treatment, and then age-hardened to further improve the strength of the material. Cold processing involves applying pressure to the material, while solid solution treatment involves heating it before slowly cooling it over time. Age hardening includes allowing the material to stand still at room temperature after solution treatment, which allows additional strengthening of the material ‘s structure over time.

Al/Al 7050 alloy can be heat treated at 477 °C (890 °F). The time spent in this process is based on the thickness of the cross section.

Heat Resistance of Aluminium 7050 (UNS A97050)

Aluminium 7050 can withstand very high temperatures without losing strength or becoming brittle. This makes it suitable for use in areas that may be exposed to extreme temperature fluctuations in hot climates or during operation. In addition, this alloy has good thermal conductivity, so it can quickly dissipate heat from key components or areas where heat accumulation problems may occur.

Corrosion Resistanceof Aluminium 7050 (UNS A97050)

Aluminum 7050 has excellent stress corrosion cracking resistance due to its combination of zinc and magnesium content. This makes it very suitable for use in environments with high humidity or salt water exposure. In addition, it has good exfoliation corrosion resistance, which makes it suitable for aircraft landing gear components and other aerospace applications. In these applications, exfoliation corrosion may be a problem.

Cold working of aluminum 7050 (UNS A97050)

Aluminum/aluminum 7050 alloy can be cold processed by traditional methods.

Aging of 7050 Aluminum (UNS A97050)

Aluminum/aluminum 7050 alloy was aged by two-stage heat treatment. Heating at 122 °C (250 °F) for 3 to 6 hours. It was heated again at 163 °C (325 °F) for 15 hours and then cooled in air.

Hardening of aluminum 7050 (UNS A97050)

Aluminum/aluminum 7050 alloy can be hardened by precipitation heat treatment.

Machining DataSheet For Aluminium 7050

Application	Turning	Milling	Parting	Grooving	Drilling
Vc (m/min)	380-620	470-780	250-415	315-520	155-260
Vc (SFM)	1250-2030	1540-2560	820-1360	1030-1710	510-850

Aluminium 7050 is relatively simple to process thanks to its good machinability rating compared to other alloys with similar strength characteristics. This alloy can be cut using standard cutting tools ( such as drills and taps ) without any significant difficulties or tool wear problems when properly machined using the appropriate speed and feed according to the given application requirements. In addition, this alloy can also be easily welded using standard welding techniques ( such as TIG welding or MIG welding ). If properly operated, there will be no obvious difficulty or warpage risk.

Application of Aluminium 7050 (UNS A97050)

7050 aluminum alloy is a high strength aluminum alloy material composed of aluminum, zinc, magnesium, copper, manganese, and other elements. It has excellent strength, toughness, corrosion resistance, and machinability. It is widely used in aviation, aerospace, military, automobile, high-speed train, and other fields.

• 1. Aeronautical field: 7050 aluminum alloy is one of the important metal materials in the aviation field. It can manufacture aircraft structural parts, hydraulic systems, landing gears, fuselage shells, and other components. It’s high strength and lightweight characteristics can reduce the weight of the aircraft and improve its performance and fuel efficiency of the aircraft.
• 2. Aerospace field: 7050 aluminum alloy is also widely used in aerospace. It can manufacture structural parts, fuel tanks, hydraulic systems, and other components of satellites, rockets, missiles, and other equipment. Its high strength and corrosion resistance can ensure the stability and reliability of the equipment in extreme environments. 
• 3. Military field: 7050 aluminum alloy is one of the important materials in the military field, which can be used to manufacture tanks, weapons, equipment, and other components. Its high strength and impact resistance can improve the defense capability and combat effectiveness of weapons and equipment. 
• 4. Automotive sector: 7050 aluminum alloy is also widely used in the automotive field which can be used to manufacture bodies, engine parts, brake systems, and other parts. Its high strength and lightweight characteristics can improve the fuel efficiency of automobiles, reduce carbon dioxide emissions, and meet the environmental protection requirements of the modern automobile industry. 
• 5. High-speed train field: 7050 aluminum alloy can manufacture high-speed train bodies, frames, suspension systems, and other components. It’s high strength and lightweight characteristics can improve the running speed and stability of the train and improve the safety and comfort of the train. 

7050 aluminum alloy has a wide range of applications and prospects and has an important position and role in various fields. With the continuous development and progress of science and technology, the application range and market demand of 7050 aluminum alloy are also increasing.

What is the difference between aluminum alloys 7050 and 7075?

Aluminum alloys 7050 and 7075 are virtually identical alloys in composition and properties. The 7xxx series of aluminum alloy alloys are well-known aluminum alloys for aerospace applications.
Both aluminum alloys use zinc as the primary alloying element. Alloy AL 7050 contains slightly more aluminum alloy (AL), copper (Co), magnesium (Mg), and zinc (Zn). In contrast, the chemical composition of AL 7075 alloy contains slightly more chromium (Cr), iron (Fe), manganese (Mn), silicon (Si), titanium (Ti), and zirconium (Zr).
Many of the performance characteristics of these two alloys are the same, including tensile strength, elongation, shear modulus, thermal resistance, and weight stiffness.
These high-strength aluminum alloy alloys may seem impeccable, but there are some limitations to their superior strength and durability when compared to other alloys. While both exhibit remarkable strength properties and are among the highest-strength aluminum alloys available, they are considered non-weldable. Their machinability could be more desirable, and their machinability is considered fair.
Both alloys are used in many outdoor products and aerospace applications where strength and weight are critical. They are relatively expensive alloys, with both materials costing almost the same.
Aluminum Alloy 7050 (AL 7050)
This aluminum alloy is prevalent in the aerospace industry, where highly stressed structural bodies require exceptional strength, resistance to stress corrosion, and toughness. AL T7050 is used for fuselage, bulkhead, and wing skins. The alloy is available in two temperings, AL 7050-7451 and AL 7050-7651.
Mechanical Properties of Aluminum Alloy 7050
The AL T7050 alloy is slightly stiffer than AL T7075 and has a slight advantage in density, toughness, corrosion resistance, and fatigue strength. It also has higher thermal and electrical conductivity values. This aluminum alloy has exceptional strength, especially in thicker sections, high resistance to stress corrosion cracking, excellent fatigue resistance, and high fracture toughness. This material is typically used for cold forging and can be heat treated or anodized.
Aluminum Alloy 7075 (AL 7075)
This aluminum alloy is produced at several temperatures, including AL 7075-0, AL 7075-T6, AL-7075-T7, AL 7085-T651, and AL7075-RRA. Interestingly, AL 7075-T6 is rapidly becoming the material of choice for sports enthusiasts. In addition to aircraft fuselages, bulkheads, and wing skins, where low weight, low strength, and high-stress resistance are critical, the alloy is frequently used in aerospace, automotive, defense, marine, and other applications.
The material is known for a variety of applications, including all-terrain vehicle (ATV) sprockets, missile parts, bicycle frames, gears, shafts, valves, keys, blow molds, golf heads, rock climbing equipment, and machinery and equipment that require the strength of AL 7075.
Mechanical Properties of Aluminum Alloy 7075
Like AL T7050, AL T7075 is compact, stronger, and lighter than steel. It is one of the strongest aluminum alloys, with a high strength-to-weight ratio. Aluminum T7075 alloy also has high corrosion resistance and slightly better tensile and shear strength than AL 7050. It also offers good resistance to spalling and stress corrosion cracking and is less sensitive to hardening.
To improve its corrosion resistance, the 7075 aluminum alloy under T6xxx tempering conditions undergoes a short, high-temperature heat treatment process called degradation and re-aging (RRA). Like AL 7050, AL 7075 can be anodized.
For structural applications such as frames, AL 7075 is particularly useful due to its high yield strength (the maximum stress a material can withstand before permanent deformation). T7075 aluminum alloy has a tensile yield strength of 503 MPa (73 KSI).

Differences between Aluminum Alloy 7050 and Aluminum Alloy 6061

Aluminum alloys are combinations of aluminum alloys with other materials such as copper, zinc, magnesium, manganese, and silicon. These alloys are designed to provide specific properties for various industrial applications. Two popular alloys used in many industries are 7050 and 6061.
Aluminum Alloy 6061
Aluminum alloy 6061 has a lower strength-to-weight ratio than aluminum alloy 7050 but still offers good corrosion resistance and weldability at an economical cost. It is often used as a structural component in railroad cars, bridges, truck frames, machine parts, etc.
Aluminum Alloy 7050
Aluminum alloy 7050 has excellent machinability but may be difficult to weld due to its tendency to crack during welding processes such as gas tungsten arc welding (GTAW). Aluminum alloy 6061, on the other hand, can be easily welded with any welding process – TIG (inert tungsten gas) welding is the most common – and offers excellent corrosion resistance when exposed to seawater or salt spray environments.
What is the difference between Aluminum Alloy 7050 and Alloy 6061?
The main difference between these two aluminum alloys is their strength. Aluminum alloy 7050 is much stronger than aluminum alloy 6061 due to its higher zinc content. It also has better fatigue resistance and resistance to stress corrosion cracking compared to Aluminum Alloy 6061. The high strength-to-weight ratio of aluminum alloy 7050 makes it ideal for aerospace applications where weight savings are critical.
Differences in Chemical Composition between Aluminum Alloy 7050 and Aluminum Alloy 6061
The first difference between Aluminum Alloy 7050 and Aluminum Alloy 6061 is their chemical composition. Aluminum Alloy 7050 is made from 97.5% aluminum, 2.4% magnesium, and 0.1% chromium. Aluminum Alloy 6061 is made from 96.3% aluminum, 1.0% magnesium, 0.6% silicon, and 0.2% chromium.
The difference in yield strength between aluminum alloy 7050 and aluminum alloy 6061
The second difference between Aluminum Alloy 7050 and Aluminum Alloy 6061 is their yield strength. Aluminum Alloy 7050 has a yield strength of 572 Mpa, while Aluminum Alloy 6061 has a yield strength of 276 MPa.
The difference in tensile strength between aluminum alloy 7050 and aluminum alloy 6061
The third difference between Aluminum Alloy 7050 and Aluminum Alloy 6061 is their tensile strength. Aluminum Alloy 7050 has a tensile strength of 690 Mpa, while Aluminum Alloy 6061 has a tensile strength of 310 MPa.
The difference in Density between Aluminum Alloy 7050 and Aluminum Alloy 6061
The fourth difference between Aluminum Alloy 7050 and Aluminum Alloy 6061 is their density. Aluminum Alloy 7050 has a density of 2.7 g/cm³, while Aluminum Alloy 6061 has a density of 2.7 g/cm³.
The difference in Cost between Aluminum Alloy 7050 and Aluminum Alloy 6061
The fifth difference between aluminum alloy 7050 and 6061 is their cost. Aluminum alloy 7050 is more expensive than aluminum alloy 6061 because it is harder to produce and has better mechanical properties.
When choosing between 7050 and 6061 aluminum alloy alloys for your project, carefully consider the application requirements before making a decision. If weight savings are important – such as when used in aerospace applications – aluminum alloy 7050 may be the right choice because it has an excellent strength-to-weight ratio. However, if you need excellent corrosion resistance or ease of weldability, then aluminum alloy 6061 may be a better choice because of its ease of use with a variety of welding processes and its corrosion resistance when exposed to salt water or other harsh environments. Ultimately, it’s important to weigh your options carefully to select the right alloy for your application.

The heat treatment process of 7050 aluminum alloy

7050 aluminum alloy is a super-hard aluminum alloy commonly used in machinery manufacturing; with high strength, good toughness, good fatigue resistance, good corrosion resistance, and other superior comprehensive performance, it can be used to make thick plates, profiles, forgings, wires, etc. The authors investigated the heat treatment process by experimental methods, analyzed the effect of heat treatment process parameters on the performance according to the experimental results, and finally compared several processes to find the optimal. The authors, through the test method of heat treatment process research, according to the test results of the heat treatment process parameters on the performance of the analysis, and finally, several kinds of process comparison, to find out the optimal program.
7050 aluminum alloy is a super-hard aluminum alloy commonly used in machinery manufacturing, with high strength, good toughness, good fatigue resistance, good corrosion resistance, and other superior comprehensive performance; it can be used to make thick plates, profiles, forgings, wires, and so on. Because of its superior performance, it is also widely used in aviation. It can make high strength, toughness, corrosion resistance, and fatigue resistance requirements of the load-bearing components, such as spacer frame, wing ribs, sorghum, wall plate, rivets, and other parts. The superior performance of this aluminum alloy is determined by its internal composition. On the one hand; on the other hand, it needs to be realized by heat treatment.

1. Material profile

7050 belongs to AI-Zn-Mg-Cu aluminum alloy; the main alloying element is zinc, but it also adds a small amount of magnesium, copper, chromium, and other elements. Zinc and magnesium are two elements that have an important role in the alloy to generate a reinforced phase; the more zinc, and magnesium content, the higher the strength of the aluminum alloy. The specific chemical composition is shown in Table 1:
Table.1 Chemical composition of 7050 aluminum alloy

Component Elements Properties	Original Value
Al	87.3 – 90.3%
Cr	≤0.04%
Cu	2.0 – 2.6%
Fe	≤0.15%
Mg	1.9 – 2.6%
Mn	≤0.10%
Other, each	≤0.05%
Other, total	≤0.15%
Si	≤0.12%
Ti	≤0.06%
Zn	5.7 – 6.7%

2. Test process

2.1 Test material and equipment
Several specimens of 7050 aluminum alloy of φ10 × 20mm, air furnace, hardness tester, and universal testing machine.
2.2 Test program
7050 aluminum alloy belongs to heat-treatable strengthened aluminum alloy, through solid solution treatment and aging strengthening to improve its performance. Solid solution treatment is a heat treatment process to heat and hold the aluminum alloy in water cooling to get a supersaturated solid solution. The higher the degree of supersaturation, the better the strengthening effect. There are many kinds of solid solution treatment processes, such as single-stage solid solution, two-stage solid solution, step-by-stage solid solution, and so on. Among them, the single-stage solid solution is characterized by a simple process, low cost, and short production cycle, and this test is mainly carried out based on the single-stage solid solution. In solid solution treatment, the two process parameters of heating temperature and holding time play a crucial role and greatly influence the final performance.
2.2.1 Influence of heating temperature in solid solution treatment
Prepare 6 aluminum alloy specimens for testing; the test program is as follows: set the solution treatment heating temperature was 465 ℃, 470 ℃, 475 ℃, 480 ℃, 485 ℃, 490 ℃, holding time of 45min, water quenching, and then artificial aging.
2.2.2 Effect of solid solution treatment holding time
Select the solid solution treatment heating temperature of 485 ℃, holding time of 25, 35, 45, and 55min, water quenching, and artificial aging.
2.2.3 Effect of the cooling medium of solid solution treatment
Prepare three aluminum alloy specimens; the test program is: set the solid solution treatment heating temperature of 475 ℃, holding time of 1h, one aluminum part with room temperature water cooling, one aluminum part with 55 ℃ hot water cooling, one aluminum parts with 66 ℃ cooling, and then artificial aging.
Aging is a heat treatment process in which the aluminum alloy, after solid solution treatment, is heated and kept warm and then air-cooled to make the supersaturated solid solution decompose and obtain a stable organization. There are two ways of aging strengthening, natural aging, and artificial aging; for 7050 aluminum alloy, artificial aging is often used. There are many kinds of aging strengthening processes, such as single-stage aging, double-stage aging, and graded aging.
The aging process strengthens the aluminum alloy because of the precipitation of the second phase, and the strengthening effect is related to the type, quantity, size, morphology, stability, and other factors of the second phase. The way, process, temperature, and time of aging will affect it, leading to differences in the final performance.
2.2.4 Influence of artificial aging heating temperature
Prepare 4 aluminum alloy specimens; the test program is solid solution temperature 475 ℃, insulation 1h, water quenching, respectively 100 ℃, 120 ℃, 130 ℃, 140 ℃ aging, insulation 24h, air cooling.
2.2.5 The effect of artificial aging holding time
Prepare five aluminum alloy specimens; the test program is solid solution temperature 475 ℃, holding 1h, water quenching, 120 ℃ aging 6h, 12h, 24h, 48h, 72h, and air cooling.

3. Test results and analysis

3.1 Effect of solid solution treatment heating temperature
The effect of solid solution treatment heating temperature on the performance is shown in Table 2. It can be seen from the data in the table as the heating temperature increases, the tensile strength and yield strength first gradually increase, the elongation is gradually reduced, and then the strength decreases, and the elongation increases. This is because as the temperature increases, the residual coarse second phase in the alloy continues to solidify, forming a supersaturated solid solution. When the heating temperature reaches 475°C, the coarse second phase decreases the most, the degree of supersaturation is the largest, and the strength is also the highest. With further increase in temperature, the grain will become coarse, or even the phenomenon of overcooking; the strength will decline. From the table, data can also be seen that although the temperature difference is not large, the performance difference is very large; therefore, in solid solution treatment, the need to strictly control the temperature to avoid the heating temperature is too low or too high resulting in low strength or overcooking phenomenon.
Table.2 Effect of solid solution treatment heating temperature on performance

Sample number	Temperature	Tensile strength (Mpa)	Yield strength (Mpa)	Elongation rate (%)
1	465 °C	540	489	15.8
2	470 °C	551	497	15.2
3	475 °C	563	512	14.5
4	480 °C	556	502	14.9
5	485 °C	547	494	15.3
6	490 °C	532	485	16.1

3.2 Influence of solid solution treatment holding time
The effect of solid solution treatment holding time is shown in Table 3. From the data in the table, it can be seen that with the prolongation of the holding time, the tensile strength and yield strength also increase, the plasticity decreases, and after reaching the peak, the strength decreases and the plasticity increases. This is because the insulation time is too short, the number of coarse second phase solidification is low, the degree of supersaturation is low, the strength is low, the insulation time is long, the number of coarse second phase solidification is high, the strength is high, the insulation time is too long, it will re-precipitate the coarse product, the strength decreases.
Table.3 Effect of solid solution treatment holding time

Sample number	Time (min)	Tensile strength (Mpa)	Yield strength (Mpa)	Elongation rate (%)
1	25	510	473	1 7.1
2	35	532	486	16.2
3	45	563	512	14.5
4	55	548	497	15.3
5	65	537	481	15.9

3.3 Effect of the cooling medium of solid solution treatment
The effect of solid solution treatment cooling medium is shown in Table 4. When using room temperature water cooling, the cooling rate is too fast, resulting in large internal stress, easy to crack or deformation; the surface of the 1st specimen produces obvious cracks visible to the naked eye; 55 ℃ hot water cooling, no cracks, the formation of supersaturated solid solution, with the temperature of the cooling medium, the second phase is not sufficiently dissolved, the strength is slightly decreased.
Table.4 Effect of cooling medium for solid solution treatment

Sample number	Cooling medium	Tensile strength (MPa)
1	Constant temperature water	Sample cracking
2	55 °C	563
3	65 °C	559

3.4 Effect of artificial aging temperature
Table.5 Effect of artificial aging temperature

Sample number	Temperature	Tensile strength (MPa)	Elongation rate (%)
1	100 °C	541	15.4
2	120 °C	563	14.5
3	130 °C	559	15.1
4	140 °C	548	15.3

The effect of artificial aging temperature is shown in Table 5. The hardness reaches the peak at 120℃; after that, with the increase in aging temperature, the strength starts to decrease gradually. This is because the aging strengthening reaches the best effect at 120°C, and the elongation is opposite to the strength trend. Aging temperature is too low, the atomic activity of low capacity, slow diffusion, affecting the formation of the solute atom-rich zone, and low strength. The aging temperature is too high; the atom diffusion is fast, which will make the supersaturated solid solution precipitation phase grow.
3.5 The effect of artificial aging time
Table.6 Effect of artificial aging time

Sample number	Time (h)	Tensile strength (Mpa)	Yield strength (Mpa)	Elongation rate (%)
1	6	503	461	16.7
2	12	545	496	15.6
3	24	563	512	14.5
4	48	527	487	16.4
5	72	496	455	17.8

Artificial aging time is too short, the number of solute atom-rich zone formations is small, and the strength is low; with the increase of aging time, the number of solutes atom-rich zone increases, the strength reaches the maximum, the strength peak occurs, after that, with the further increase of aging time, the size of the precipitated phase increases, the strength decreases, the elongation rises.

4. Conclusion

Through the analysis of the test results, this conclusion can be obtained:
With the gradual increase of solid solution heating temperature, the tensile strength and yield strength of 7050 aluminum alloy gradually increase. At the same time, the elongation gradually decreases, and the peak strength occurs at 475℃ solid solution, after which the strength decreases and the elongation increases.
Solid solution heating temperature is unchanged; with the prolongation of holding time, the tensile strength and yield strength of 7050 aluminum alloy gradually increased and then reached the peak; the holding time continued to extend, and the strength began to decrease gradually.
Solid solution treatment heating temperature and holding time unchanged, using different cooling methods, cooling speed is too fast, 7050 aluminum alloy easy to crack, cooling speed is too slow, then the strength is lower.
With the gradual increase of artificial aging temperature, the tensile strength of 7050 aluminum alloy firstly increases gradually; the elongation gradually decreases, and the strength peaks at 120℃ aging, after which the strength decreases and the elongation increases.
Under the condition of constant aging heating temperature, with the prolonged holding time, the tensile strength and yield strength of 7050 aluminum alloy gradually increase and then reach the peak. The holding time continues to be prolonged, and the strength decreases gradually.
It can be seen that the parameters of solid solution treatment and aging play a vital role in changing the properties of 7050 aluminum alloy. How to make good use of these process parameters, further improve and optimize the heat treatment process, and improve the comprehensive performance of 7050 aluminum alloy is an issue that we need to continue to study in depth.
Author: Li Zaohua