Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 24    No. 7    July 2014

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Continuous cooling precipitation diagram ofhigh alloyed Al-Zn-Mg-Cu 7049A alloy
Davit ZOHRABYAN1,2, Benjamin MILKEREIT1,2, Christoph SCHICK2, Olaf KESSLER1

1. Chair of Materials Science, University of Rostock, 18051 Rostock, Germany;
2. Polymer-Physics Group, University of Rostock, 18051 Rostock, Germany

Abstract:The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate (0.0005 to 5000 K/s). The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry (DSC) techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed: a high temperature reaction in a narrow temperature interval of 450-430 °C, and a low temperature reaction in a broad temperature interval down to about 200 °C. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry (DFSC) and the differential reheating method (DRM). A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.

 

Key words: differential scanning calorimetry (DSC); differential fast scanning calorimetry (DFSC); 7049A alloy; differential reheating method; continuous cooling precipitation

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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