The effect of zinc on microstructure and solidification characteristics of Al-Zn-Mg-Cu alloys

Abstract

In this study, the effect of zinc on microstructure and solidification characteristics of super high strength Al-Zn-Mg-Cu has been investigated. The solidification studies were performed using cooling curve thermal analysis. This method represents quick and accurate results of solidification path of an alloy. The microstructure studies showed increment in the amounts of zinc increases the dendrite arm spacing (DAS), fraction of second phases and eutectic structure and results in a coarse dendrite structure. However, the zinc content did not affect the present phases in this alloying system. Thermal analysis evaluations revealed decrease in nucleation temperature with zinc addition. The formation of Al13Fe4 phase was observed using cooling curve. The solidification range in the presence of 8wt.% of zinc was 175 °C although the adding of zinc up to 25 wt.% increased it to 190 °C. Cooling curves represented the increase of the fraction of eutectic structure which was in accordance with image analysis results. The addition of zinc resulted in the decrease of the solidified fraction at dendrite coherency point from 0.32 to 0.1 which matched by increment in porosity fraction from 0.09 to 0.32

Full text

Winter 2019, Volume 21, number 4

Spring 2016, Volume 19, Number 1
METALLURGICAL ENGINEERING
The Journal of Iranian Metallurgical and Materials Engineering Society
hp:metalleng.ir/ 4
Hot deformaon of an extruded Mg–10Li–1Zn alloy was studied by compression tesng in the temperatures range of 250-
450˚C and strain rates of 0.001–0.1s−1. During hot compressive deformaon of the Mg-10Li-1Zn alloy, ow stress curves
reach a maximum value and then reach a steady state which is indicave of the occurrence of dynamic recrystallizaon. Be-
cause of the acvaon of soening mechanisms at higher temperatures and lower strain rates, this phenomenon is more
pronounced at lower temperatures and higher strain rate. The ow stress of the Mg–10Li–1Zn alloy at elevated tempera-
tures was modeled via an Arrhenius-type constuve equaon. The values for the acvaon energy of about 103 kJ mol–1
and the power-law stress exponents in the range of 5.2–6.0 obtained from the Arrhenius-type model indicate that the domi-
nant mechanism during hot deformaon of the Mg–10Li–1Zn alloy is dislocaon climb which is controlled by the lace
self-diusion of Li atoms.
Key words: Mg-Li alloys, Hot deformaon, Constuve equaons
A B S T R A C T
Citation:
Shalba M, Roumina R, Mahmudi R. The Study of Hot Deformation Behavior of an Mg-10Li-1Zn Alloy by Arrhenius Conitutive
Equations. Metallurgical Engineering. 2016; 19(1):4-12. http://dx.doi.org/10.22076/me.2017.27135.1030
:
: http://dx.doi.org/10.22076/me.2017.27135.1030
* Corresponding Author:
Reza Roumina, PhD
Address:
School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
Tel: +98 (21) 82084097
E-mail: roumina@ut.ac.ir
Research Paper
The Study of Hot Deformaon Behavior of an Mg-10Li-1Zn Alloy by Arrhenius Constuve
Equaons
1. MSc., School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
2. Assistant Professor, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
3. Professor, School of Metallurgy and Materials Engineering, University of Tehran, Tehran, Iran.
Mostafa Shalba1, *Reza Roumina2, Reza Mahmudi3
* Corresponding Author:
Mehdi Malekan, PhD
Address:
School of Metallurgy and Materials Engineering,University of Tehran, Tehran, Iran.
Tel: +98 (21) 82084610
E-mail: mmalekan@ut.ac.ir
Research Paper
The eect of zinc on microstructure and solidicaon characteriscs of Al-Zn-Mg-Cu alloys
Saman Mostafapoor1, *Mehdi Malekan2, Masoud Emamy3
1- MSc, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran, Tehran, Iran.
2- Assistant Professor, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran, Tehran, Iran.
3- Professor, Metallurgy and Materials Engineering, School of Metallurgy and Materials Engineering,University of Tehran, Tehran, Iran.
Citation: Mostafapoor S, Malekan M, Emamy M. The effect of zinc on microstructure and solidication characteristics of Al-Zn-Mg-Cu
alloys. Metallurgical Engineering 2019: 21(4): 252-263 http://dx.doi.org/ 10.22076/me.2019.83388.1180
doi : http://dx.doi.org/ 10.22076/me.2019.83388.1180
ABSTRACT
In this study, the eect of zinc on microstructure and solidicaon characteriscs of super high strength Al-Zn-Mg-Cu has been
invesgated. The solidicaon studies were performed using cooling curve thermal analysis. This method represents quick
and accurate results of solidicaon path of an alloy. The microstructure studies showed increment in the amounts of zinc
increases the dendrite arm spacing (DAS), fracon of second phases and eutecc structure and results in a coarse dendrite
structure. However, the zinc content did not aect the present phases in this alloying system. Thermal analysis evaluaons re-
vealed decrease in nucleaon temperature with zinc addion. The formaon of Al13Fe4 phase was observed using bycooling
curve. The solidicaon range in the presence of 8wt.% of zinc was 175 °C although the adding of zinc up to 25 wt.% increased
it to 190 °C. Cooling curves represented the increase of the fracon of eutecc structure which was in accordance with image
analysis results. The addion of zinc resulted in the decrease of the solidied fracon at dendrite coherency point from 0.32
to 0.1 which matched by increment in porosity fracon from 0.09 to 0.32.
Keywords: Al-Zn-Mg-Cu alloy, Solidicaon, Thermal analysis, Cooling curve, microstructure.

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     
       


     










CACCA

    
–
     

        
DTA       

      



1. Computer Aided Cooling Curve Analysis
2. Dierenal Thermal Analysis



Al-Zn-Mg-Cu

   
AlSiAlSi
–AlSiCu  –AlCu –Mg

  AlZnMgCu   

 
    DCP    
   
         





      




      
xAl-xZn-2.5Mg-2.5Cu




   AlZnMgCu  
Al-50%Mg  %    
Al-50%Cu
3. Dendrite Coherency Point

          


     
  

°Cs


K



     

AlZnMgCu

%.wt
ZnMgCuSiFeAl
A8

A10

A12

A15

A17

A20

A25







     ADAM-4000 
   b9.2.257  OriginPro





= +
ct
T a be
cba tT

      





−


= =

−


∫
∫
s
e
s
t
cc zc
t1
st
cc zc
t
dT dT
() ()dtt
dt dt
fdT dT
() ()dt
dt dt
1
t
fs
 
 


 
TWTC

DCP


ASTM E3-11


     4.1.1.0 

PHILIPSXRD
KɑÅ
 


4. Curve Fing
5. Digimizer
6. X-ray Diracon


Vega©Tescan
EDS
     


       
ISO 2738
MelerToledoGreifensee
       



  AlZnMgCu     

       
        
      
    

 
μm      
     
μm


   
μm


         
 AlSiCu 




     
  A20  A15 A8  
        
       
  
     AlZnMgCu 
7. Energy Dispersive X-ray Spectroscopy
8. The role of mixtures



Al-Zn-Mg-Cu
       
EDS

AαAl
 B MgZn2η αAl  

AlZn

C        
 Al2MgCuS
  Al2Zn3Mg3T 
  E      D 
θ    F 
     Al2Cu

A20A17A15A12A10A8
A15EDS


 AlZnMgCuFe
A
αAl
B
ηαAl
C

S(Al2MgCu)
D

T(Al2Mg3Zn3)
E

T(Al2Mg3Zn3)
F

θ(Al2Cu)
G

Al13Fe4
Al-Zn-      
Mg-Cu




AlZnMgCu

  Al13Fe4     
    
A15A8
A20


XRDXRD
A20 A15A8
MgZnAlCu2MgZn2ηɑ-Al
Mg32AlCu49T
θS 

A20A15A8XRD
 

MgZn2
 Mg(Zn,Al,Cu)2
  TMg32(Al,Cu)49
          S θ


EDSA15




Al
Zn
Mg
Cu
Fe
A




-
α-Al
B




-
α-Alη
C




-
S(Al2MgCu)
D




-
T(Al2Mg3Zn3)
E




-
T(Al2Mg3Zn3)
F




-
θ(Al2Cu)
G





Al13Fe4



200
300
400
500
600
40 50 60 70 80 90 100
Temperature oC
Zinc, wt%
Liquid
a
b
a+Liquid
382
o
443o
275o
69.5
80.5
95
a'
71.6
a+b
340o
b+h
b+Liquid
h
420o
86.5
a+h




Al-Zn-Mg-Cu

     A15   
  



       





Al-15Zn-2.5Mg-2.5Cu

AlZnMgCu 

       

     
        


       
AlZnMgCu


   

        
Tmin
        


TG
TG
ɑ
Tmin
TG
°CA8TGTminTN
°C °C
 
AlZn
 °C   °C °C 

TE
TN
ΔTN

      


°C°C
       

A15     
   °C  
   TR      
        
  °C   C°  TR   
   
αAlAl-9.2Zn-xMg-2.3Cu
°CC°







   
        

 

        
       η αAl
SαAl TαAl 
TNE  
    
        
   °C
°C
       




Al13Fe4
  °C     7050  
Al13Fe4

9. Xie
Al13Fe4 (TR)



Al-Zn-Mg-Cu

        
        



    





        
Ts
        
   



   
TS
          
   
     
 °C         °C
         
         
       
 A8°C
    °C    

 °C
tft1




AlNiSi





A15
TcTw

TwTc
DCP

fDCP


A8 
     
    

         
  
    
DCP      
         

       
       DCP  
         

ts∆TsTS





  Al-15Zn-2.5Mg-2.5Cu
DCP

DCP
  
DCP 




        




DCP


tDCPTDCP
DCP
°C

DCP°C

DCP
DCP

DCP
TNTDCPDCP

°C   
°C

A15DCP
DCP
AlZnMgCu

DCPTNTDCP




Al-Zn-Mg-Cu
DCP
DCP



 

μm
μm
 
°C°C
°C°C
°C°C
         
Al13Fe4
         
°C°C
 DCP       


DCP

 

 


 


 °C  °C  

AlZnMgCu


        

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