AlSi10MnMg is a European aluminium alloy grade, also known as EN AC-43500, derived from Silafont-36 of the German Ryanaluminium company. The Si content of this aluminium alloy is slightly lower than that of Al-Si eutectic alloy and has better fluidity. When the Fe content is less than 0.15%, the plate shape of the Al, Fe and Si phases can be eliminated so that the die casting does not crack under stress. A certain Mn content can also prevent the alloy from sticking to die casting, and the microstructure appears spherical. Therefore, aluminium alloy belongs to a kind of high strength and toughness aluminium alloy, which is widely used in structural parts, especially automobile structural parts, in the aspect of replacing steel with aluminium. The different control ranges, heat treatment processes and production conditions in the standard components can get a wide range of different die-casting mechanical properties. To find out the corresponding process accurately located in the performance and achieve the goal of the composition control range and heat treatment process selection based on the performance, we have conducted many experiments and research. The different contents of Mg and the orthogonal test of different heat treatment states are taken as the breakthrough point and applied to aluminium alloy structural parts with different performance requirements. This paper is mainly based on experimental data for analysis and research. The elongation rate is the measured elongation rate after breaking, and the elongation rate is higher if calculated by an extension meter.
Influence of different Mg content on mechanical properties of die casting
The aluminium alloy grade belongs to the AlSi10Mg group in the European Union standard; Mg is the main heat treatment strengthening element. Its authoritative content is from 0.1-0.5%, a relatively wide range. This gives us a good range to adjust for the pursuit of strength properties, especially the combination of strength and elongation. According to the analysis of the experimental data, the general law with the change of Mg content is: Mg content is positively correlated with the tensile strength and yield strength and negatively correlated with the elongation. Table 1 shows the experimental data of die casting in the F state.
Its changing trend is shown in Figure 1.
In the heat treatment state, Mg content also affects the mechanical properties of die casting. Table 2 shows the experimental data of die casting in the T6-9 state. Its changing trend is shown in Figure 2.
Influence of different heat treatment states on mechanical properties of die casting
The heat treatment process given by the German Ryan aluminium company is a relatively wide range, and the specific application should be selected and adjusted according to the actual situation. According to the influence degree of Mg content on the mechanical properties of die casting, we divided Mg content into four sections, H, A, B and C, to carry out various heat treatment experiments. The sample forming method is ordinary die casting; the performance will be better if vacuum die casting is used.
T6 Heat treatment
T6 heat treatment can obtain the highest strength and relatively ideal elongation performance. The samples with different Mg content were subjected to T6 heat treatment, and orthogonal tests were carried out on four factors, such as solution temperature (480-490 ℃), holding time (2-5h), ageing temperature (155-170 ℃), ageing and holding time (2-5h). In the experiment, not only can the heat treatment process of this section be optimized, but also various combination schemes of different strength and toughness performance indexes in this section are obtained.
The performance range of segment A after T6 is shown in Table 3.
The experimental index data of several combined performances in this section are shown in Table 4.
The performance range of segment B after T6 is shown in Table 5.
The experimental index data of several combined performances in this section are shown in Table 6.
The performance range of segment C after T6 is shown in Table 7.
The experimental index data of several combined performances in this section are shown in Table 8.
Similarly, the performance range after T6 of the special H segment is obtained by experiment (omitted). The above experimental data shows the performance distribution range of the four Mg contents after T6 in FIG. 3.
T7 Heat treatment
T7 heat treatment process after solution through over-ageing can maximize the high elongation performance. Similarly, the samples with different Mg content were subjected to T7 heat treatment. Orthogonal tests were carried out on four factors, such as solution temperature (470-490 ℃), holding time (1-5 h), ageing temperature (190-230 ℃), and ageing and holding time (1-3h). The optimal heat treatment process of each section was found, and various combination schemes of each section’s strength and toughness properties were obtained. The specific experimental analysis method is similar to T6 (omitted). The performance range of the four Mg contents after T7 is shown in FIG. 4.
T5 Heat treatment
The effect of T5 heat treatment is to increase the strength and reduce the elongation appropriately compared with the die-casting F state. Various ageing processes were used to explore the Mg content of different sections, and the following results were obtained:
2.3.1 Tensile strength, yield strength and elongation increase with ageing time at the same ageing temperature. For example, when the ageing temperature is 185℃, the effect of ageing time on the performance is shown in Figure 5, Figure 6, Figure 7 and Figure 8.
At the same ageing time, with the ageing temperature, increasing, the tensile strength and yield strength increase while the elongation decreases. See Figure 9, Figure 10, Figure 11 and Figure 12 for the effect of ageing temperature on performance.
With the increase of Mg content in the same ageing process, the tensile strength,
The yield strength increased while the elongation decreased. For example, when the T5-8 process is adopted, the mechanical properties of die casting with different Mg content ranges are shown in Table 10 and Figure 13.
Application of main mechanical properties of die casting with different heat treatment states of Mg content in each section
The effects of the T4 and O annealing state on the properties of ordinary die-casting samples with different Mg sections were also studied by the same method.
The experimental results of various states are summarized in table9
In various heat treatment states, the experimental data in Table 9 are compared with the data of the German Ryan Aluminum company. The index range of adaptive performance is wider, and the specific process control range of selecting performance in the application is narrower and easier to locate accurately.
If Volkswagen has a component whose performance requirements are tensile strength ≥ 300MPa, yield strength ≥ 250MPa and elongation ≥ 7%, there is a specific T6 scheme for AlSi10Mn Mg material produced by our company. In addition, if the performance of a subframe requires tensile strength ≥ 290MPa, yield strength ≥ 210MPa, and elongation ≥ 5%, specific complementary schemes are available for implementation in T5 and T6. Al Si10Mn Mg material produced by our company has been sampled and tested on the body of die-casting subframe after T5 heat treatment and has passed the performance index. Another example is the performance requirements of automobile shock absorber tower tensile strength ≥ 200MPa, yield strength ≥ 140MPa, elongation ≥ 10%, and the corresponding T6 and T7 groups of programs can be achieved.
As long as the user gives the performance requirements of the application of the aluminium alloy brand, you can choose the corresponding composition range and production process to control the production, and provide the aluminium alloy material at the same time, provide the corresponding heat treatment process of die casting. It also provides economic alternatives when more than two implementations exist simultaneously.
AlSi10Mn Mg aluminium alloy material, with increased Mg content, the tensile strength and yield strength increased, and the elongation decreased. And vice versa.
Different heat treatment states or process parameters in the same heat treatment state have different effects on the mechanical properties of die casting.
For different Mg content and different heat treatment process, the specific control scheme of different performances after subdivision can be obtained by combining the production melting process. It is beneficial to select the corresponding smelting production and heat treatment process plan according to the different performance requirements of high-strength and structural toughness parts.
The subdivided control scheme, when multiple groups of schemes can meet the requirements of the same performance index, is also conducive to economic selection considering the cost factor.