基于厚向組織性能考量的7B50鋁合金中厚板回歸再時效熱處理

侯隴剛; 趙鳳; 莊林忠; 張濟山

doi:10.13374/j.issn2095-9389.2017.03.016

基于厚向組織性能考量的7B50鋁合金中厚板回歸再時效熱處理

doi: 10.13374/j.issn2095-9389.2017.03.016

1) 北京科技大學新金屬材料國家重點實驗室, 北京 100083
2) 山東南山鋁業股份有限公司, 龍口 265706

基金項目:

國家自然科學基金資助項目（51401016）；北京市教委共建資助項目

詳細信息

中圖分類號: TG146.2
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出版歷程
- 收稿日期: 2016-05-12

Retrogression and re-aging 7B50 Al alloy plates based on examining the through-thickness microstructures and mechanical properties

1) State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
2) Shandong Nanshan Aluminium Co. Ltd., Longkou 265706, China

摘要

摘要: 為解決T6態高強鋁合金強度高而耐蝕性難以滿足使用需求，采用三級時效工藝來改善析出強化相特別是晶界析出相的形貌、尺寸、分布等，并通過研究不同回歸處理制度對組織、性能的影響而獲得適宜7B50鋁合金中厚板的三級時效工藝.研究發現提高回歸溫度或延長回歸時間均會使中厚板心部及表層組織的晶內和晶界析出相發生粗化并析出穩定η-MgZn₂相，導致強度下降、電導率上升，其中回歸溫度對強度和電導率的影響顯著.三級時效處理雖使晶內析出相尺寸有所增加，但卻使T6態連續分布的晶界析出相呈斷續分布，結合心部和表層強度及電導率測量結果認為合適的回歸處理制度為165℃/6 h.然而，熱軋引起中厚板表層較心部更為嚴重的變形使表層含有更多的亞晶或亞結構且其分布更均勻，從而使表層更快到達峰時效，進一步的回歸再時效處理則使表層析出更多穩定η相，而η相的形成與晶內析出相的粗化長大是造成表層和心部強度差異的關鍵.雖然淬火/三級時效態表層和心部的晶粒結構存在差異，且局部出現亞晶合并長大，但其對強度的提升效果遠低于表層析出穩定η相所引起的強度下降.可見，三級時效工藝并不能緩解7B50鋁合金中厚板心部和表層的性能差異，但可使表層和心部的強度、電導率滿足某實際工況要求.
- 鋁合金 /
- 回歸 /
- 再時效 /
- 組織 /
- 性能 /
- 析出
Abstract: For enhancing the corrosion resistance of the T6-aged high-strength Al alloys with higher strength, retrogression and reaging (RRA) treatments were used to optimize the morphologies, sizes, distribution of precipitates, especially grain boundary precipitates (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 precipitation 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 treatment, 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.
- aluminum alloy /
- retrogression /
- re-aging /
- microstructure /
- properties /
- precipitation

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參考文獻(25)

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