The APS aluminum aging phenomenon of regression is analysed characteristics and matters needing attention | | industry information
aluminum aging characteristics and considerations for a regression, regression characteristic by natural aging reinforced aluminum alloy profiles, rapid heating to 210 ~ 250 ℃ temperature, short time heat preservation ( 30～300s) , and then rapidly cooling to room temperature, the alloy to soften, restore to the new quenching condition, such as the parking at room temperature, is still able to normal natural aging. This phenomenon is called regression. Such repeat the above process can be repeated to return. The return of hard aluminum alloy profiles. Regression phenomenon is, in fact, after the natural aging of aluminium alloy profile generated by the GP zone or metastable phase, dissolved in rapid short-term heated, into the original state of quenching. Aluminum profile and performance also returned to the performance of the new quenching condition. Regression phenomenon has the following features: 1) Every natural ageing strengthening of aluminum profile with regression phenomenon. 2) Return process can be repeated many times. As shown in figure 3 & ndash; 5 - 12, after each regression process, its performance is not fully restored to the original state, there is always a little gap. 3) Return to deal with the higher the temperature, the faster the return process, shorter heating time required. 4) After regression treatment of the alloy, and its corrosion resistant performance declined. 2, return to deal with some problems that should be paid attention to by regression treatment to restore the plastic problem that should be paid attention to: 1) Regression processing temperature must be higher than that of the original aging temperature, the greater the difference, the faster the return, the more thoroughly. If both difference is very small, regression is hard to happen, even will not happen. 2) Return to deal with the heating time is generally shorter, as long as the low temperature desolventizing is completely dissolved. If the time is too long, there will be a corresponding to the temperature desolventizing phase, make the hardness increase or aging, can not meet the regression results. 3) Regression in the process, only precipitated phase of GP area ( A1— Cu alloy including theta 'phase) To dissolve, precipitated phase of product is often difficult to dissolve. Due to the limitation of low inevitably there will always be a small amount of precipitated phase of the product in the place such as grain boundary precipitation, so even in the best of times, alloy cannot be completely back to the new quenching condition, there is always a small amount of the change of nature is not reversible. This can lead to mechanical properties a certain loss, and easy to make the alloy produces intergranular corrosion. Therefore it is necessary to control the number of regression processing. Regression phenomenon in industry has important practical application value. Can put the return to natural ageing strengthening of aluminum profile, and make the processed after softening. Such as many type, aluminum alloy profile bar bending forming by regression for processing after processing, airplane rivet, riveting regression after processing, and then let the natural aging increase strength. Three, return again aging treatment used to think that only natural aging of the alloy can be return processing. In l974 to B. M。 Cina first proposed, aluminum alloy profiles of artificial aging state of aluminum alloy profiles can also return to processing, then repeat the original artificial aging. The heat treatment process called regression and aging treatment. This process is applicable to Al— Cu— 毫克,Al— Mg— 如果,Al— 锌- Mg— Cu alloy. Such as Al— 锌- Mg— Cu in the department of 7075 alloy, with a single peak aging ( T6) Can achieve the highest tensile strength, but less resistance to stress corrosion. In order to improve the stress corrosion resistance USES hierarchical limitation, which is 110 ℃ ageing, thermal insulation 8 h, then l77 ℃ ageing, thermal insulation 8 h, the result can improve the stress corrosion resistance, but strength was reduced by 10% ~ l5 %. Using regression and aging treatment, can remain 7075 T6 alloy high strength, and have good stress corrosion resistance of grading aging treatment.