1. solid solution strengthening
Alloy elements are added into pure aluminum to form an infinite solid solution or a finite solid solution, which not only achieves high strength, but also obtains excellent plasticity and good pressure performance. The most commonly used alloy elements for solid solution strengthening in general aluminum alloys are copper, magnesium, manganese, zinc, silicon, nickel and other elements. In general, alloying of aluminum all forms limited solid solutions, such as Al-Cu, Al-Mg, Al-Zn, Al-Si, Al-Mn and other two alloy all form finite solid solution, and have greater limit solubility, which can play a larger role in solid solution strengthening.
2. aging hardening
The supersaturated aluminum based solid solution can be obtained after heat treatment of aluminum alloy. The strength and hardness of this supersaturated aluminum solid solution increase with time and extension at room temperature or heating to a certain temperature, but the plasticity decreases. This process is called the timeliness. The phenomenon of increasing the strength and hardness of the alloy during the aging process is called aging hardening or aging hardening.
3. superfluous phase enhancement
When the water content of the alloy added to aluminum exceeds its limit solubility, a second part of the alloy can not be dissolved into solid solution when it is quenched and heated, which is called an excess phase. In the aluminum alloy, the excess phase is mostly hard and brittle intermetallic compound. They impede the movement of slip and dislocation in the alloy, and increase the strength and hardness, while the plasticity and toughness decrease. The more the excess phase in the alloy is, the better the strengthening effect is, but the strength and plasticity of the alloy will be reduced due to the brittle alloy.
4. refine tissue enhancement
It is another important means to improve the mechanical properties of aluminum alloy with the addition of micro elements in the aluminum alloy.
The addition of trace titanium, zirconium, beryllium, strontium and rare earth element deformation Aluminum Alloy, they can form refractory compounds, as non self crystal nucleus in alloy crystallization, grain refinement effect, improve the strength and ductility of the alloy.
A trace element is often added to the cast aluminum alloy to refine the alloy structure and improve the strength and plasticity. The modification is of special significance to the cast aluminum alloy and the deformed aluminum alloy which can not be enhanced by heat treatment. For example, the addition of sodium or sodium salt or antimony as a modifier in Al Si cast aluminum alloy can be modified to improve the plasticity and strength of the aluminum alloy. Similarly, adding a small amount of manganese, chromium, cobalt and other elements in the cast aluminum alloy can make the plate or needle like compounds AlFeSi refined and improve plasticity. The addition of Trace Strontium can eliminate or reduce the primary silicon and make the eutectic silicon refined.
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