Evolution of intermetallic phases of Al-Zn-Mg-Cu alloy during heat treatment

• Published in: Transactions of Nonferrous Metals Society of China Vol. 16; no. A03; pp. 1247 - 1250
• Main Author: 樊喜刚 蒋大鸣 孟庆昌 李念奎 孙兆霞
• Format: Journal Article
• Language: English
• Published: Analysis and Measurement Center, Harbin Institute of Technology, Harbin 150001, China%Northeast Light Alloy Co Ltd, Harbin 150060, China 01.12.2006
• Subjects: 有色金属; 金属相; eutectic structure; intermetallic particles; phase transformation; Al-Zn-Mg-Cu alloy
• ISSN: 1003-6326
• DOI: 10.1016/S1003-6326(07)60001-6

Al-Zn-Mg-Cu alloy is a favorable choice for aerospace applications requiring good combination of strength and toughness, which is greatly influenced by the coarse intermetallic particles. The evolution of intermetallic particles in an Al-Zn-Mg-Cu alloy during heat treatment was studied by field emission gun scanning electron microscopy （FEG-SEM） and X-ray diffractometry（XRD）. The results show that there are lamellar eutectic structure （α（Al）＋Mg（Zn,Al,Cu）：） and Al7Cu：Fe particles in the solidified structure. The Al7Cu2Fe particles are embedded in the eutectic structure. The content of eutectic structure decreases with the increase of holding time and disappears after 24 h. The size and morphology of Al7Cu：Fe particles exhibit no change during the heat treatment. It is found that the AI：CuMg phase is formed during the treatment at 460 ℃. A transformation process from the primary eutectic phase Mg（Zn,Al,Cu）2 to Al2CuMg is observed, and the transformation mechanism and kinetics are analyzed, The AI：CuMg constituents form in the primary Mg（Zn,Al,Cu）： phase, and grow along the eutectic microstructure.