(1. 北京科技大学 新金属材料国家重点实验室，北京100083；
2. 宝山钢铁股份有限公司 中央研究院 宝武铝业技术中心，上海 201900；
3. 中国宝武三门峡铝基新材料研发中心，三门峡 472000)
摘 要: 通过SEM、TEM观察及性能测试等手段研究了Al-Mg-Si-Cu-(2.0%Zn)合金析出和抗晶间腐蚀行为。结果表明：添加Zn可有效促进预时效态合金185 ℃时效初期硬化速率和峰值强度(峰值硬度、屈服强度和抗拉强度分别可达1200 MPa、313.9 MPa和358.8 MPa)，但是伸长率却降低不明显，SEM断口形貌呈典型的塑性断裂特征；添加2.0%Zn的峰时效态合金还具有优异的抗晶间腐蚀性能，最大晶间腐蚀深度可由不含Zn合金的90 μm降低至40 μm。TEM组织表征显示，溶质元素Zn的添加可以显著促进合金晶内和晶界沉淀相的析出，晶内仍以Mg-Si沉淀相为主，而晶界附近分布有Mg-Zn沉淀相，偏离晶界较远处却分布有由多种元素构成的AlMgSiCuZn沉淀相；基于组织和性能演化规律，提出了含2.0%Zn合金晶内和晶界沉淀析出过程模型图，及其相关抗晶间腐蚀影响作用机制。
关键字: Al-Mg-Si-Cu-Zn合金；时效响应；峰时效；晶间腐蚀；模型；机制
（1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China;
2. Baowu Aluminum Technical Center, Baosteel Central Research Institute, Baoshan Iron & Steel Co., Ltd., Shanghai 201900, China;
3. Sanmenxia Aluminum-based New Material Research & Development Center, China Baowu Steel Group, Sanmenxia 472000, China）
Abstract:In this work, the precipitation and corrosion behaviors of Al-Mg-Si-Cu-(2.0%Zn) alloys were studied through SEM, TEM characterization and mechanical property and intergranular corrosion measurements. The results reveal that Zn addition can greatly improve the initial age hardening rate and peak aging strengths, the peak hardness, yield and ultimate tensile strengths are 1200 MPa, 313.9 MPa and 358.8 MPa, respectively, but the elongation is only reduced a little bit, and ductile fracture is the main fracture feature as observed by SEM examination of fracture surface. Additionally, the peak aged Al-Mg-Si-Cu alloy added 2.0%Zn also possesses an excellent resistance ability to occur, the intergranular corrosion, the deepest corrosion depth can be reduced from 90 μm for the Zn-free alloy to the value of 40 μm. According to the TEM microstructure characterization, it has been found that Zn addition can greatly improve precipitation rates of phases formed within grains and grain boundaries, Mg-Si precipitates are still the main precipitates formed within the grains, while both Mg-Zn precipitates near the grain boundaries and AlMgSiCuZn precipitates are the main precipitates formed around the grain boundaries under the Zn-added alloy in the peak aging condition. Based on the microstructure evolution and properties, the schematic diagram of forming precipitates within the grains and around the grain boundaries and the intergranular corrosion mechanism of the two Al-Mg-Si-Cu alloys were put forward in this paper.
Key words: Al-Mg-Si-Cu-Zn alloys; aging hardening response; peak aging; intergranular corrosion; modelling; mechanism
