You are not logged in Total: 7journals, 20,314articles Online
AccountAccount
Login / Register
Forgot Login?
 
Main menuMain menu
What's new
Journal list
Visiting ranking
Phrase ranking
Polls
About us
 
SearchSearch
 
Journal Site
Advanced Search
 

Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.56  No.11 (2015)  >  pp.1771-1780

MATERIALS TRANSACTIONS
<<Previous article Vol.56  No.11 (2015)   pp.1771 - 1780 Next article>>

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

JaeHwang Kim1), Equo Kobayashi1), Tatsuo Sato2)
1) Department of Metallurgy and Ceramics Science, Tokyo Institute of Technology 2) Precision and Intelligence Laboratory, Tokyo Institute of Technology

Nanoclusters formed during natural aging cause the negative effect of the two-step aging in the age-hardenable Al-Mg-Si alloys. The relationship between the clustering behavior during natural aging and the two-step aging behavior was studied using the hardness, differential scanning calorimetry (DSC), electrical resistivity measurements, transmission electron microscopy (TEM) observation in the Cu-free and Cu-added Al-Mg-Si alloys. Three stages during the two-step aging are clearly revealed based on the hardness results. The hardness in the two-step aging with the natural aging time is decreased, increased and then decreased at the initial, middle and final stages, respectively. Si-rich clusters initially formed during natural aging do not transform into the β′′ phase and are thermally stable during the two-step aging at 170°C. On the other hand, Mg-Si co-clusters formed at the middle stage during natural aging transform into the β′′ phase and are thermally unstable during the two-step aging at 170°C. Much higher hardness is obtained in the Cu-added alloy than that of the Cu-free alloy during two-step aging when natural aging is performed for 3.6 ks belonging to the initial stage. The higher hardness is also found to be obtained during over-aging regardless of the natural aging time in the Cu-added alloy than that of the Cu-free alloy. The relationship between the clustering behavior during natural aging and the two-step aging behavior is discussed based on the observed age-hardening phenomena.


Keyword:
aluminum alloys, precipitation hardening, two-step aging, cluster

Received: June 03, 2015
Accepted: August 19, 2015 , Published online: October 25, 2015

PDFPDF file (J-STAGE)J-STAGEJ-STAGE


SPARC Japan

Terms of Use | Privacy Policy