(中国航空制造技术研究院，材料应用研究部，北京 100024)
摘 要: 800 MPa级超高强Al-Zn-Mg-Cu合金对航空结构轻量化具有重要意义，但存在断裂伸长率波动较大的问题。本文提出了双级峰时效制度，系统对比了120 ℃单级时效、80 ℃一级时效和120 ℃二级时效处理后的微观组织和力学性能。结果发现：双级时效过程中，经一级时效处理后合金基体内析出了高密度的GP区，促进后续二级时效过程中晶内形成细小弥散的η′相，并减小了晶界无析出带宽度；二级时效时间在8-10 h之间时，合金强度最高且伸长率在10%以上。晶界无析出带宽度减小是伸长率提高的直接原因。
关键字: 超高强铝合金；预时效；析出相；晶界无析出带；伸长率
（Department of Materials Application Research, AVIC Manufacturing
Technology Institute,Beijing 100024, China）
Abstract:The ultra-high strength Al-Zn-Mg-Cu alloy of 800 MPa is of great significance to the lightweight of the aviation structure, but the fracture elongation fluctuates greatly at present. In this paper, a two-stage peak ageing process was proposed. The microstructures and mechanical properties of the alloys treated by single-stage ageing at 120 ℃, first-stage ageing at 80 ℃ and second-stage ageing at 120 ℃ were systematically compared. The results show that after the first-stage ageing treatment, high-density GP zones precipitate in the matrix, which promotes the formation of fine dispersion η′ phase during the second-stage ageing process. Compared with the single-stage ageing state, the width of precipitation free zone (PFZ) at grain boundary is reduced. When the second ageing time is between 8-10 h, the strength is the highest and the elongation is more than 10%. The decrease of the width of PFZ at grain boundary is the direct reason for the increase of elongation.
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