Encyclopedie de la recherche sur l'aluminium au Quebec - Edition 2014 | Page 77

TRANSFORMATION ET APPLICATIONS // TRANSFORMATION AND APPLICATIONS

75

Hot Workability and Processing Maps of 7150
Aluminum Alloys DÉFORMATIONV Additions CARTOGRAPHIE DU PROCESSUS
with Zr and À CHAUD ET
DES ALLIAGES D'ALUMINIUM 7150 AVEC AJOUT DE Zr ET V
（Déformation à chaud et cartographie du processus des alliage
HOT WORKABILITY AND
d'aluminium 7150 avec ajout de Zr et V）

PROCESSING MAPS OF 7150
ALUMINUM ALLOYS WITH Zr AND V ADDITIONS

Cangji Shi, X.-Grant Chen
NSERC/Rio Tinto Alcan Industrial Research Chair
in Metallurgy of Aluminum Transformation, UQAC

1. INTRODUCTION

5. RESULTS

Due to a high strength-to-density ratio and excellent mechanical
properties, the 7xxx aluminum alloys have been widely used in the
automotive and aerospace industries. Trace additions of Zr and V
have been reported to increase material strength combined with a
reasonable toughness. To establish optimum processing conditions
and improve mechanical properties, an understanding of the effects
of alloying elements on the hot workability of the alloy is required.

5.1. Flow stress curves
(a)

(a)

2. OBJECTIVES

A0.15 Zr

Base alloy

¥  Investigate the variations in processing maps of 7150 aluminum
alloys with different Zr additions (0 to 0.15 wt.%) and V additions
(0.01 to 0.15 wt.%).

5.2. Initial microstructure

(b)

(b)

(d)

(c)

¥  Study the microstructural evolution to understand the effects of
Zr and V additions on the processing maps and on the dynamic
deformation mechanisms under various deformation conditions.

Fig.2. (a) TEM image of Al3Zr dispersoids
in A0.12 Zr; (b) STEM image of Al21V2
dispersoids in A0.11 V.

A0.15 V
A0.05 V
Fig.1. Typical true stress-true strain curves.

5.3. Processing maps

3. PRINCIPLE OF PROCESSING MAP

A0.04 Zr

Efficiency of power dissipation:

η=

2m
2m +1

A0.12 Zr

A0.15 Zr

A0.05 V

A0.11 V

A0.15 V

Criterion of flow instability:

ξ=
﹒

∂ln[m / (m +1)]
+m<0
!
∂ln ε

ε : strain rate;
σ : true stress;
m : strain rate sensitivity.

∂ln σ
m=
!
∂ln ε

4. EXPERIMENTAL PROCEDURES
Base alloy

Table 1. Chemical compositions of the alloys studied

Casting

Chemical composition, wt.%
Material
Zn

Mg

Cu

Si

Fe

Zr

V

Al

0.15

-

0.01

Bal.

A0.04 Zr
6.27 2.14 2.23 0.11

0.14 0.04 0.01

Bal.

A0.12 Zr
6.35 2.22 2.34 0.16

0.15 0.12 0.01

Bal.

A0.15 Zr
6.16 2.15 2.16 0.11

0.14 0.15 0.01

Bal.

A0.05 V
6.21 2.18 2.20 0.16

0.14

-

0.05

Bal.

A0.11 V
6.31 2.30 2.24 0.16

0.14

-

0.11

Bal.

A0.15 V
6.16 2.10 2.15 0.16

0.13

-

0.15

Bal.

A (7150
base alloy) 6.44 2.47 2.29 0.16

5.4. Microstructure characterization
Base alloy

A0.15 Zr

A0.05 V

A0.15 V

DRX

DRV

DRX

DRV

Domain I

=100 µm; Map3; Step=1 µm; Grid380x250

=100 µm; Map3; Step=1 µm; Grid380x250

Microstructure
characterization

¥ EBSD (Electron backscatter
diffraction)

¥ OM
¥ SEM
¥ TEM

Hot compression test
(Gleeble 3800 system)

¥ Temperature: 300-450 °C
¥ Strain rate: 0.001-10 s-1

cracks

Homogenization
treatment

¥ Temperature: 465 °C
¥ Time: 24 h
¥ Water quench

=100 µm; Map3; Step=1 µm; Grid380x250

cracks

cracks
=100 µm; Map3; Step=1 µm; Grid380x250

Domain II

Cangji Shi
X.-Grant Chen
CRSNG/Rio Tinto Alcan,
Chaire industrielle en
métallurgie de la
transformation de l’aluminium
(CIMTAL),
Université du
Québec à Chicoutimi

ASBs
ASBs

Flow
instability
region

DBs

ASBs
DBs

ASBs
DBs
DBs

6. CONCLUSIONS
¥  The processing map of the 7150 base alloy exhibits a single domain (Domain I). With increasing Zr and V additions, Domain I shrinks towards higher temperatures and higher strain rates and
exhibits decreases in efficiency of power dissipation.
¥  When the added Zr and V contents reach 0.15%, another domain (Domain II) is formed, corresponding to cavity formation in the microstructure.
¥  Flow instability during hot deformation of 7150 alloys is attributed to the formation of adiabatic shear bands and deformation bands.
¥  The optimum hot-working parameters for those alloys are determined to be a deformation temperature of 450 °C and a strain rate of 0.01 s-1.

Journée des étudiants – The effects of Zr (0.04 to 0.15 wt % ) and V additions (0.05 to 0.15 wt % ) on the
REGAL

Les effets de l’addition du Zr (de 0.04