(中國航空制造技術(shù)研究院，材料應(yīng)用研究部，北京 100024)
摘 要: 800 MPa級超高強Al-Zn-Mg-Cu合金對航空結(jié)構(gòu)輕量化具有重要意義，但存在斷裂伸長率波動較大的問題。本文提出了雙級峰時效制度，系統(tǒng)對比了120 ℃單級時效、80 ℃一級時效和120 ℃二級時效處理后的微觀組織和力學(xué)性能。結(jié)果發(fā)現(xiàn)：雙級時效過程中，經(jīng)一級時效處理后合金基體內(nèi)析出了高密度的GP區(qū)，促進(jìn)后續(xù)二級時效過程中晶內(nèi)形成細(xì)小彌散的η′相，并減小了晶界無析出帶寬度；二級時效時間在8-10 h之間時，合金強度最高且伸長率在10%以上。晶界無析出帶寬度減小是伸長率提高的直接原因。
關(guān)鍵字: 超高強鋁合金；預(yù)時效；析出相；晶界無析出帶；伸長率
（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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