Aluminum 6061 T6 vs T651 vs T6511: What is the Difference?

Aluminum alloys are available in many grades and it is not an easy task to differentiate between them. This article provides you with a comparison of two of the most used tempering processes being used for aluminum alloys. 6061 tempered alloys have the same composition but have different mechanical properties such as machinability, formability and hardness values. Here you will be able to grasp their respective heat treatment process parameters and have an idea about when you will require a specific tempering process. After understanding the pros and cons of each process you will be able to make the decision according to your application requirements.

Discover the key differences between 6061 T6 and 6061 T651 and 6061 T6511 aluminum alloys in our comprehensive comparison guide. Unleash the full potential of these high-performance alloys and make informed decisions for your next project.

What is 6061 T6 Aluminum

T6 aluminum alloys which are known by their high strength and exceptional mechanical properties are being used in various industrial applications. Along with alloy elements, tempering can also be used to improve the properties of an alloy. Aluminum T6 have excellent corrosion resistance and good weldability.

T6 aluminum machined parts are commonly used in the aerospace and automotive industries due to its high strength and corrosion resistance.

Aluminum T6 Temper

There are about five designations for tempering in Aluminum alloys. T is used for thermally treated alloys, the digit which used next to ‘T’ is for a specific heat treatment process. In T6 Aluminum temper first the solution is heat treated followed by artificial aging.

6061 T6 Aluminum Heat Treatment Process

First of all, the alloy’s solid solution is made by heating it for one hour at 525 ⁰C. This makes the alloy fully homogenous in solid state. After this the alloy is quenched in water, which hinders the formation of precipitates. So, every alloying element is present as a solid solution at room temperature. The rapid quenching is not purposefully done for strengthening the alloy but increases the strength. Following diagram is showing the microstructure of aluminum 6061 t6 temper.

Now if you heat this alloy at a temperature range of 162-205 ⁰C, alloying elements start to precipitate and form order arrays that are called GP zones which provide adequate strength to aluminum alloys. The heating time ranges from 1 hour at 205 ⁰C and 8 hours at 162 ⁰C, these different heating rate at different temperature give almost same results.

This youtube link will help you in better understanding of heat treatment in industries:

Aluminum 6061 T6 Mechanical Properties

After applying T6 temper to aluminum the yield strength increases almost four times as compared to 0-tempered aluminum. For example, 6061 0-temper has Yield strength of 55 MPa and tensile strength of 125 MPa. Whereas t6 temper has the least value of yield strength equals to 240 MPa and tensile strength of at least 290 MPa. So, their high strength and low weight give them an edge over other alloys and they are being used in various industries.

Due to its high strength to weight ratio, good weldability and corrosion resistance it is the most used aluminum alloy. Following are the major applications of T6 temper aluminum

1. Due to its excellent corrosion resistance, it is used in watercrafts.
2. Commercial and military aircrafts.
3. Bicycle frames.
4. Automobiles components.
5. Fishing reels and fire fighter ladder.

Pros and Cons of 6061 T6 Aluminum

Advantages

1. T6 temper provides you with high strength and like other aluminum grades it is light weight.
2. T6 tempering gives you excellent corrosion resistance and good weldability.
3. It also has better formability and machinability as compared to other high strength aluminum alloys.

Disadvantages

1. These ideal properties come with complex heat treatment process, and you have to carefully check the parameters such as heating rate, time and temperature.
2. This special heat treatment also makes it much expensive than other aluminum grades such as T5.
3. T6 temper also reduces the ductility of the sample.

Much thicker samples of aluminum cannot be heat treated effectively due to uneven cooling during T6 temper. So, this tempering process should be modified for thick samples which would save time and material.

Definition 6061 T651 Aluminum

Aluminum T651 is basically the subset of T6 temper. It has better processability as compared t6 tempered alloys. When you have to deal with machining processes such as grinding, polishing and cutting T651 temper come in handy.

Aluminum T651 Temper

T651 temper is achieved initially by making the solid solution, after that stress reliving is done by stretching the material and finally artificial aging is done to achieve this temper.

T651 Aluminum Heat Treatment Process

Heat treatment of T651 is a bit different from T6 temper. It has one additional step of stress relieving after quenching in water. Then aging is done in the similar way as in T6 tempering.

During solution heat treatment internal stresses gets entrapped in the alloy. To remove these stresses stretching is done by mechanically elongating the sample (cooled stretching) with the help of stretching machine. This step improves alloy dimensional stability which helps it retain its shape during different processing. Diagram below is showing the microstructure of T651 6061 aluminum alloy.

Aluminum T651 Mechanical Properties

Aluminum 6061 has same mechanical properties such as tensile strength, hardness and elastic modulus. So high strength to weight ratio and hardness is retained after this tempering which makes it more suitable for processing.

 When the external force is detached during the processing you are only left with internal stresses. These internal stresses will cause the recovery effect which will produce a noticeable change in size.

T651 is extensively used in fixed devices (aerospace & electrical), thick plates, die-forging, precision machining, mold making and automobile parts.

Pros and Cons of 6061 T651 Aluminum

Advantages

1. Retention of all the best properties offered by T6 temper. Such as it is light weight, weldable, corrosion resistant and has high strength.
2. During machining processes T651 temper is preferred, because it helps material not to deform after processing and increases the dimensional stability.

Disadvantages

1. Due to an additional step in heat treatment the cost of this process is more than t6 temper.
2. Processing time is also increased as a result of an extra step of controlled stretching.

Understand pros and cons of aluminum T651 to better and faster carry out your project, or consult China Tuofa mechanical engineer to contact info@tuofa-cncmachining.com

Physical properties: Difference Between 6061 T6 and T651 

T651 has better machinability than that of T6 temper. T651 also shows less distortion after processing and is preferred in areas where complex shapes and high accuracy is required. It is also more expensive as compared to T6 temper alloys. The chart below shows the comparison between these two tempers.

Aluminum 6061 Temper Chart

As a professional mechanical engineer from Tuofa CNC Machining, I'd like to share a detailed Aluminum 6061 Temper Chart with you. This chart will provide valuable insights into the various tempers of Aluminum 6061, a widely used material in precision CNC machining for its excellent strength-to-weight ratio and corrosion resistance.

Here is a comprehensive chart for your reference:

Mechanical Properties: 6061 T6 vs 6061 T651

Heat treating 6061 aluminum using different ways will change the mechanical properties without altering the alloying elements. Al 6061 T6 vs T651 comparison is given below.

Strength

Aluminum 6061 T6 and T651 have same tensile strength near to 310 MPa. Also, they have same density so have high strength to weight ratio. This is because only stretching is done during the heat treatment without changing rest of the parameters.

Heat treatment

After heating up to 980 F for an hour and then quenching in water, artificial aging is done. This is the case during T6 temper. When the alloy is quenched in water residual stresses are entrapped inside the sample. This is because of the uneven cooling of core and surface. In T651 temper after quenching the sample is 1 to 3 % stretched with the help of stretching machine to get those residual stresses out of the sample.

Dimensional stability contrast

Dimensional stability is retained more in 6061 T651 aluminum plates. Due to absence of internal stresses machining of aluminum alloy can be done without distorting the final sample. T6 temper has high strength but there is significant distortion taking place in the sample during machining processes.

Applications for 6061 T6 VS T651 VS T6511

T651 due to its dimensional stability and high machinability is used in complex application. Both of them are popular in the industry and have relatively more usage than any other aluminum alloy.

Aluminum 7075 T6 vs T651

Aluminum 7075 T6 and T651 are the different grades of same alloy. They have similar alloy composition but their heat treatment process is different so they have been assigned with different graded of T651 and T6.

They have different mechanical properties due to different processing. For example, yield and tensile strength of T651 are little bit higher than that T6 7075 aluminum material. T651 has lower percentage elongation as compared to T6 alloy. You can view more comparisons of material characteristics of aluminum 7075 and 6061.

To choose between these tempers you may watch this you tube video:

Machinability and Fabrication

The biggest advantage of using T651 temper is the easy of machining and fabrication over T6 temper. No distortion takes place during processes like forging, cutting and milling etc. So, material retain its shape after processing.

Difference Between 6061 t6 and 6061 t651 and 6061 T6511

When to Choose: Aluminum 6061 T6 or 6061 T651 or 6061 T6511

6061 T6 Aluminum

You will choose T6 temper if we have the following requirements:

1. Hight strength to weight ratio is required: T6 temper provides you with sufficient amount of hardness and strength, and can be used in heavy load bearing applications.
2. When machining processes needed for the fabrication of the parts are less in numbers and complexity T6 temper is favored.
3. Last but not the least budget constraint is also very crucial for the selection of the right process. T6 temper is cheaper as compared to T651.

6061 T651 Aluminum

Following are the industries or applications where t651 is preferred:

1. If you need to improve the machinability of Aluminum alloys T651 tempering is done by controlled stretching.
2. If you need high dimensional stability after machining processes T651 is the required tempering process. Removal of internal stresses also remove distortions. This makes it a candidate for automation and robotics industry.
3. Controlled stretching also improves the weldability of the aluminum alloy, so where superior welding is required T651 temper is done.

6061 T6511 Aluminum

Aluminum T6511 is the ideal choice for applications that demand an exceptional combination of high strength and outstanding straightness. This temper is produced through a rigorous process that includes solution heat treatment, artificial aging, cold working, and minor straightening. This multi-step process results in an aluminum alloy with exceptional dimensional stability and resistance to deformation under load.

Due to the additional processing steps involved in creating T6511, it is generally more expensive than T6 or T651. However, for applications where the demanding requirements justify the higher cost, T6511 is the preferred choice.

Conclusion

Small change in heat treatment process became the reason for improving important mechanical properties. Solid solution making, age hardening processes are done in the same manner, although in T651 stretching is also done before quenching which makes the machinability and formability much better than before.

Understanding these differences, both alloys are selected for the application aligning with the given properties. T651 is superior in welding, machinability and dimensional stability. But it has a complex heat treatment process and also high cost. So, if you need to have zero compromise on these properties T651 should be selected. But if you can compromise on these properties, you should save some cost and use t6 alloy which is less expensive. T651 is best suit for the fabrication of thick plates, milling and die forging.

If you require fair machinability and formability you should go with T6 temper because it is readily available and less costly.

Ams 4173 are basically 6061 aluminum alloys or low alloy steels. It stands for Aerospace Material Specification and gives you the complete profile of the material in respect to its properties. ASTM b209 standard is allocated for aluminum and its alloys. It has guidelines about composition, heat treatment specification for making sheets, plates etc.

CNC machined aluminum parts can be used in automotive parts, aerospace materials, machinery and industrial equipment. T651 is preferred for this machining because of the desired mechanical properties. You should consult China Tuofa for CNC machining because Tuofa uses different manufacturing technologies in making parts precisely and swiftly. Engineers in Tuofa advise you choose the best process for different materials for a specific application. Facilities like functional prototyping, affordable pricing, low-volume production and high-performance components with a very little distortion are made.

FAQs

6061 t651 round bar

6061 t651 round bars are made by many industries through the same t651 temper. The are specially designed for application such as fire protection systems, shipping equipment, petrochemical and steel industries.

6061-T651 specification

Following are the mechanical specifications of 6061 T651 aluminum alloys.