Alloy 5251 belongs to the Al-Mg system with low magnesium and cannot be strengthened by heat treatment. It has good corrosion resistance, weldability, medium strength and good plasticity, and is easy to be processed and formed.
In foreign countries, 5251 aluminum alloy sheets with different heat treatment states are the main materials used in automobile manufacturing, canning industry and other fields; in China, so far, the complete technical data of 5251 aluminum alloy H2n and 0-state sheets have not been formed, and their production The process technology has not been formed, and the alloy sheet is not much produced in China.
Combining with market demand and production practice, we study the influence of annealing temperature and holding time on the microstructure and properties of 5251 aluminum alloy sheet after medium temperature rolling, determine the production process and heat treatment system of its H2n and 0 states, and produce aluminum alloys that meet the EN485 standard. plate.
Ⅰ Test scheme 1.1 Test material test A 5251 aluminum alloy ingot with a cross-sectional dimension of 255mmx1500rnm produced by semi-continuous water-cooling casting method is selected, and its chemical composition meets the requirements of Table 1. Table 15251 aluminum alloy chemical composition (mass fraction) % other impurities Si Fe Cu Mn Mg Cr Zn Ti individual total 0.40.50.150.1~0.51.7~184.108.40.206.150.050.15 In 5251 aluminum alloy, training (Mg) Between 1.7% and 2.4%.
Magnesium is the main strengthening element, which exists in the form of solid solution and |3 phase, and plays a certain role in solid solution strengthening. The solid solubility of magnesium in aluminum is 17.4% at 450cC and 1.9% at 100aC. Although the solubility of magnesium in the alloy decreases rapidly with the decrease of temperature, the aging strengthening effect of the alloy is low due to the difficulty in nucleation of the precipitation phase, the few cores and the large precipitation particles. Magnesium enhances the work hardening sensitivity of aluminum, and the alloy can obtain obvious strain strengthening. Manganese and chromium play a supplementary strengthening role.