Encyclopedie de la recherche sur l'aluminium au Quebec - Edition 2014 | Page 67

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Precipitation of Al3Zr dispersoids in AA7150
PRÉCIPITATION DES DISPERSOÏDES Al3Zr DANS L'ALLIAGE
Al alloy during two-step homogenization
D'ALUMINIUM AA7150 PENDANT L'HOMOGÉNÉISATION EN DEUX ÉTAPES
Précipitation des dispersoïdes Al3Zr dans
l’alliage d’aluminium AA7150 pendant Al3Zr DISPERSOIDS IN AA7150 Al
PRECIPITATION OF
l’homogénéisation en deux étapes
ALLOY DURING TWO-STEP HOMOGENIZATION
Zhanying Guo, X.-Grant Chen
NSERC/Rio Tinto Alcan Industrial Research Chair
in Metallurgy of Aluminum Transformation, UQAC

As recrystallization inhibitor, small quantities of Zr are added into
7xxx series Al alloys, which forms fine Al3Zr dispersoids during
homogenization. However, the precipitation of Al3Zr dispersoids often
concentrates in the center of dendrite gains and the precipitate free
zone (PFZ) of dispersoids forms in dendrite grain boundaries. In
current study, a two-step homogenization was designed to improve
the overall distribution of Al3Zr dispersoids in AA 7150 Al alloy.

Alloy

Zn

Mg

Cu

Zr

Fe

Si

Ti

Al

5.99

1.91

2.10

0.09

0.13

0.11

0.01

Bal.

First step
Homogenization
300 ºC x 48 h, 72 h
400 ºC x 48 h, 72 h

Two-step

Investigating precipitation behavior of Al3Zr dispersoids after the
first step homogenization in AA 7150 aluminum alloy.

homogenization

Second step
homogenization

Investigating the overall precipitation behavior of Al3Zr dispersoids
after two-step homogenization in AA 7150 aluminum alloy.

(b)

(c)

(d)

(b)
Homogenization
parameters

(c)

470 oC /24h
oC
300(f) /48h＋470 oC /24h
(g)
300 oC /72h＋470 oC /24h
oC /48h＋470 oC /24h
400
400 oC /72h＋470 oC /24h

(e)

Fig. 1. Typical TEM centered dark field images of size and distribution of Al3Zr
dispersoids in AA7150-0.09Zr Al alloy after one-step and two-step homogenization:
(a) 470 o C/24h, (b) 300 o C/48h＋470 o C/24h, (c) 300 o C/72h＋470 o C/24h,
(d) 400 oC/48h＋470 oC/24h, (e) 400 oC/72h＋470 oC/24h.

(a)

(b)

(a)

Conventional TEM with twobeam diffraction conditions,
Centered dark filed images:
oriented along low index [011]
zone axis of Al matrix and (200)
L12 superlattice reflection.

Table 1. Measured average radius, number density, volume fraction of Al3Zr
dispersoids in AA7150-0.09Zr Al alloy after both on