工程科学学报2017，Vol.39Issue(3)：432-442,11.DOI:10.13374/j.issn2095-9389.2017.03.016
基于厚向组织性能考量的7B50铝合金中厚板回归再时效热处理
Retrogression and re-aging 7 B50 Al alloy plates based on examining the through-thick-ness microstructures and mechanical properties
摘要
Abstract
For enhancing the corrosion resistance of the T6-aged high-strength Al alloys with higher strength, retrogression and re-aging ( RRA) treatments were used to optimize the morphologies, sizes, distribution of precipitates, especially grain boundary precipi-tates ( GBPs) . The effects of different retrogression treatments on the microstructures and mechanical properties were studied so as to gain suitable RRA process for 7B50 Al alloy plates. It is found that increasing the retrogression temperature or time will promote the coarsening of transgranular and intergranular precipitates in the center and surface layers of 7B50 Al alloy plates as well as the precipi-tation of stable η-MgZn2 phase, which will decrease the strength and raise the conductivity. The retrogression temperature will greatly affect the strength and conductivity. The continuously distributed GBPs induced by T6 aging become discontinuous after RRA treat-ment, accompanying with slightly increasing sizes of transgranular precipitates. Based on the strength and conductivity of the center and surface layers, 165℃/6 h is the suitable retrogression process for 7B50 Al alloy plates. However, the severe deformation of the surface grains compared to that of the central grains caused by hot rolling leads to a higher content of subgrains or substructures in the surficial grains, which promotes the surface layer to quickly reach the peak aging, and the subsequent retrogression treatment results in much more stable η phase in the surface layer. The formation of stable η phase as well as the coarsening or growth of transgranular precipitates could be mainly responsible for the strength difference between the surface and center layers. Although there are some differences about the grain structures between the surface and center layers after quenching/RRA treatments with some local subgrain growth, the positive impact of RRA treatment to the strength is apparently unable to compare with the obvious strength reduction caused by early precipitation of stable η phase in the surface layer. Thus, the RRA treatment cannot relieve the property difference between the center and surface layers of 7B50 Al alloy plates, but it can make the strength and conductivity of the center and surface layers to concurrently meet some working requirements.关键词
铝合金/回归/再时效/组织/性能/析出Key words
aluminum alloy/retrogression/re-aging/microstructure/properties/precipitation分类
矿业与冶金引用本文复制引用
侯陇刚,赵凤,庄林忠,张济山..基于厚向组织性能考量的7B50铝合金中厚板回归再时效热处理[J].工程科学学报,2017,39(3):432-442,11.基金项目
国家自然科学基金资助项目(51401016) （51401016）
北京市教委共建资助项目 （）
