J Mater Sci Technol ›› 2010, Vol. 26 ›› Issue (2): 141-145.

• Light Weight Metals • Previous Articles     Next Articles

Effects of Pre-Ageing Treatment on Subsequent Artificial Ageing Characteristics of an Al-1.01Mg-0.68Si-1.78Cu Alloy

Lizi He, Haitao Zhang, Jianzhong Cui   

  1. Key Lab of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004, China
  • Received:2008-07-23 Revised:2009-07-08 Online:2010-02-28 Published:2010-02-28
  • Contact: Lizi He
  • Supported by:

    the National Key Technology R&D Program of China under grant No. 2007BAE38B01.

Abstract:

The influences of pre-ageing temperature and natural ageing time on subsequent artificial age hardening behavior and precipitation sequence of new type Al-1.01Mg-0.68Si-1.78Cu alloy were investigated by hardness test, differential scanning calorimetry (DSC) test and transmission electronic microscopy (TEM) observations. When pre-ageing temperature is 20°C (natural ageing), the peak hardness of subsequent artificial aged alloy is lower than that of T6 treated alloy (negative effect), while a positive effect appears when pre-ageing temperature is above 80°C. The size of needlelike β-precipitate in subsequent artificial aged alloy is much coarser when pre-ageing temperature is 20°C, which causes a decrease in peak-hardness. The positive effect occurs again when natural ageing time is longer than 3 weeks. There are seven exothermic peaks in DSC curve of as-quenched alloy, while the number and height of exothermic peak decrease with increasing pre-ageing temperature and natural ageing time.

Key words: Al-Mg-Si-Cu alloy, Pre-ageing treatment, Age hardening, Differential scanning calorimetry (DSC) curve