Experimental Studies on Mechanical Properties of 6070 Aluminum Alloy Forged Parts along Different Metallic Flows
Abstract
This paper reports experimental investigations of the mechanical properties of 6070 aluminum alloy forged parts along different metallic flow directions. The specimens used in the test were obtained from 6070 aluminum alloy forgings manufactured by hot die forging. Tensile, bending, torsion and impact tests were conducted according to the corresponding standard test for each direction of parts. The test results showed that the static and dynamic mechanical properties of the samples in the rolling direction were better than those in the transverse directions. The tensile strength and yield strength in the rolling direction were higher than those in the horizontal and vertical directions, and the elongation was lower. In the experiment of torsion test, the maximum torsion results of samples in the horizontal, vertical and rolling directions were 1192.2N·mm, 1202.3N·mm and 1277.9N·mm respectively. The secondary bending strength of samples in the horizontal direction was slightly lower than those in the vertical and rolling directions, and the elastic modulus was slightly higher than that of the vertical and rolling directions. The impact toughness of samples in three directions were all within the requirements for the corresponding standard, with the highest impact energy absorption in the rolling direction. The experimental results provided the necessary data reference for the application of 6070 aluminum alloy forging parts in structural materials.
Keywords: 6070 aluminum alloy forgings, rolling direction, transverse direction, mechanical properties
1 Introduction
Aluminum alloy is a silvery white metal, chemically active and easily combined with oxygen and other elements to form a variety of cast and forged components with different mechanical properties and technological properties[1]. The 6070 alloy system, developed by the German engineer Suhl-PeK, is an aluminum-magnesium-silicon-magnesium alloy, also known as AL-Mg-Si-Mn alloy[2]. 6070 alloy has many kinds of alloy indicators, including tensile strength, yield strength, elongation, torsion strength, impact toughness and fatigue limit, elastic modulus and hardness, etc., which fully comply with the requirements of the aircraft, ship, automobile and home appliance manufacturing fields, etc. As a structural material, 6070 aluminum alloy forgings can be used in a wide range of applications. Forgings are one of the main methods of processing 6070 aluminum alloy materials[3]. With numerical control machine core moulds, die forgings can reach complex shapes with high dimensional accuracy and good surface quality. The obvious differences in component shape and internal structure of forgings and castings have an important influence on their mechanical properties.
In the forging process, due to different flow directions of metal, the distribution characteristics of metallurgical microstructure, grain size and mechanical properties vary in different parts, and the mechanical properties in the rolling direction are better than those in the transverse directions[4]. In general, it is believed that the mechanical properties in rolling direction are better than those in the transverse directions. However, due to the lack of corresponding experimental research, the different directions of components and the relationship between mechanical properties are not clear. In order to verify the mechanical properties of 6070 aluminum alloy forgings in different directions and provide the basis for selecting 6070 aluminum alloy forgings for structural materials, the tension, bending, torsion, impact and other tests were conducted on the forgings obtained from 6070 aluminum alloy in this study. The mechanical properties of 6070 aluminum alloy forgings in three directions were obtained.
2 Experimental
2.1 Materials
The 6070 aluminum alloy forgings used in the experiment were produced by die forging from hot forgings. The chemical composition of the material is as follows (wt. %): Al-4.7 Mg-4.4 Si-0.4 Mn-0.7 Ti-0.28, the tensile strength is 535MPa, and the hardness is 62HB. The tensile strength and yield strength of matrix material meet the requirements of ASTM B25-22[5], and the microstructure is shown in Figure 1.
Figure 1. The SEM micrograph of the matrix material
2.2 Test Equipment
The mechanical properties tests of 6070 aluminum alloy forgings include tensile test, bending test, torsion test and impact test, respectively. The tensile test was carried out on the LZG200 servohydraulic universal testing machine manufactured by the Zhengzhou University Testing Institute, the bending test was carried out on the LZG100 servohydraulic bending machine manufactured by the Zhengzhou University Testing Institute, and the torsion test was carried out on the LDZ10 single column test machine manufactured by the Laser Corporation.
2.3 Procedures
2.3.1 Tensile Test
According to ASTM E8-11a standard[6], the flat specimens with dimensions of Φ10 × 40 mm were prepared from the 6070 aluminum alloy forging in three directions, respectively. Then the tensile test of 6070 aluminum alloy forgings in three directions was carried out on the LZG200 servohydraulic universal test machine. The displacement control speed is 2 mm/min.
2.3.2 Bending Test
According to ASTM E290-10a standard[7], specimens of width 25.4 mm and thickness 5 mm were cut from the 6070 aluminum alloy forging in three directions, respectively. Then the bending test of 6070 aluminum alloy forgings in three directions was conducted on the LZG100 servohydraulic bending test machine, and the maximum load, elastic modulus and secondary bend angle of the specimens were measured.
2.3.3 Torsion Test
According to ASTM E 836-14 standard[8], the torsion test specimens of Φ10mm, gauge length 100 mm and width 20 mm were prepared from 6070 aluminum alloy forgings in three directions, respectively. Then the torsion test of 6070 aluminum alloy forgings was conducted on the LDZ10 single column torsion test machine, and the maximum torque, elastic modulus and twist angle at fracture were measured.
2.3.4 Impact Test
According to ASTM E 23-10 standard[9], the specimens of Φ10 mm×50 mm were cut from 6070 aluminum alloy forgings with three different flow directions, respectively. The specimens were then placed along the axis of the machine to conduct the impact test on the LDZ10 single column impact test machine. The energy absorption value of the specimens facing different flow directions was measured in the test.
3 Results and Discussion
3.1 Tensile Test
The tensile test results of 6070 aluminum alloy forgings in three directions are shown in Table 1. The tensile strength in the rolling direction was about 30% higher than that in the transverse directions, and the yield strength was about 17% higher. The elongation at fracture of the sample in rolling direction was lower than that in horizontal and vertical directions, while the reduction of area at fracture was higher in the rolling direction than in other directions.
Table 1. Tensile test results of 6070 aluminum alloy forgings
3.2 Bending Test
The results of bending test of 6070 aluminum alloy forgings in three directions are shown in Table 2. The maximum bending strength in the rolling direction was slightly higher than that in the horizontal and vertical directions, and the elastic modulus in the rolling direction was slightly lower than that in the horizontal and vertical directions. This indicates that, for a certain forging process, the forging deformation of the sample in the rolling direction leads to a certain degree of plastic deformation, which makes its mechanical properties better than those in the transverse directions.
Table 2. Bending test results of 6070 aluminum alloy forgings
3.3 Torsion Test
The results of torsion test of 6070 aluminum alloy forgings in three directions are shown in Table 3. The maximum torsion results in other directions were lower than that in the rolling direction, which indicates that the roll forging in the rolling direction leads to a certain degree of plastic deformation, which makes its mechanical properties better than those in the transverse directions.
Table 3 Torsion test results of 6070 aluminum alloy forgings
3.4 Impact Test
The results of impact test of 6070 aluminum alloy forgings in three directions are shown in Table 4. the test results showed that the impact energy absorption of the sample in the rolling direction is the highest among the three directions, it was about 10% higher than that of the horizontal direction and 8% higher than that of the vertical direction. The impact energy absorption of the specimens in all directions meets the requirements of the corresponding standards, indicating that 6070 aluminum alloy forgings in three directions have good impact resistance.
Table 4. Impact test results of 6070 aluminum alloy forgings
4 Conclusion
In this study, the static and dynamic mechanical properties of 6070 aluminum alloy forgings in three directions were tested. The results showed that the tensile strength and yield strength in the rolling direction were higher than those in the horizontal and vertical directions, and the elongation in the rolling direction was lower than that in the other two directions. The torsion strength results of samples in three directions were 1277.9N·mm, 1192.2N·mm and 1202.3N·mm respectively, and the maximum bending strength results in the horizontal direction were slightly lower than those in the vertical and rolling directions. The impact energy absorption of the specimens in three directions were all within the requirements for the corresponding standard, and the impact energy absorption of the sample in the rolling direction was the highest. The test results provided
