[China Aluminum Industry Network] Aluminum alloy reinforcement methods are mainly the following: 1. Solid solution strengthening Aluminum alloy elements are added to form an aluminum-based solid solution, which causes lattice distortion and hinders the movement of dislocations. It plays a role of solid solution strengthening and can increase its strength. According to the general rule of alloying, when an infinite solid solution or a high concentration solid solution type alloy is formed, not only high strength can be obtained, but also excellent plasticity and good pressure processing performance can be obtained. Al-Cu, Al-Mg, Al-Si, Al-Zn, Al-Mn and other binary alloys generally can form limited solid solution, and all have greater ultimate solubility (see Table 9-2), and therefore have a larger Solid solution strengthening effect. 2. Another reinforcing effect of aging-hardening alloying elements on aluminum is achieved by heat treatment. However, since aluminum does not have allotropic conversion, its heat treatment phase transition is different from that of steel. The heat treatment of the aluminum alloy is mainly due to the greater solid solubility of the alloying elements in the aluminum alloy, and decreases sharply as the temperature decreases. Therefore, after the aluminum alloy is heated to a certain temperature and quenched, an oversaturated aluminum-based solid solution can be obtained. When this supersaturated aluminum-based solid solution is placed at room temperature or heated to a certain temperature, its strength and hardness increase with time, but plasticity and toughness decrease, and this process is called aging. The aging at room temperature is called natural aging, and aging under heating conditions is called artificial aging. The phenomenon of increasing the strength and hardness of the aluminum alloy in the aging process is called aging strengthening or age hardening. Its strengthening effect depends on the age hardening phenomenon produced during the aging process. 3. Excess phase strengthening If the amount of alloying elements added to the aluminum exceeds the limit solubility, there is a second phase that does not dissolve in the solid solution when the solution heats up, which is called the excess phase. In aluminum alloys, these excess phases are usually hard and brittle intermetallic compounds. They hinder the dislocation movement in the alloy and strengthen the alloy, which is called super phase strengthening. This method is often used in production to strengthen cast aluminum alloys and heat-resistant aluminum alloys. The greater the number of surplus phases and the more dispersed the distribution, the greater the strengthening effect. However, too much of the excess phase will reduce the strength and plasticity. The more complex the structure of the excess phase components, the higher the melting point, the better the high-temperature thermal stability. 4. Refinement of tissue reinforcement Many aluminum alloy structures consist of alpha solid solutions and excess phases. If the microstructure of the aluminum alloy can be refined, including refining the α solid solution or refining the excess phase, the alloy can be strengthened. Because the microstructure of the cast aluminum alloy is relatively coarse, the metamorphic treatment method is often used to refine the alloy structure in actual production. In the modification treatment, a modificator (commonly used sodium salt mixture: 2/3 NaF+1/3 NaCl) is added to the molten aluminum alloy in the amount of the alloy before casting to increase the crystallization core and refine the structure. The modified aluminum alloy can obtain a fine uniform eutectic plus a primary α solid solution structure, thereby significantly increasing the strength and plasticity of the aluminum alloy.