Muddiest  Points      Phase  Diagrams  IV:  Fe-­‐Fe3C  Phase  Diagram  Calcula;ons  

 Muddiest  Points:    •     “In  a  two  phase  region  how  can  composi;on  be  determined  by  looking  to  either  side  of    the    two-­‐phase  region?”  

•     “Where  do  you  get  the  numbers  from  on  the  phase  diagram  to  do  the  calcula;on?”  

•  “I'm  s;ll  a  liGle  unclear  on  how  to  calculate  the  frac;on  of  each  phase”  

•  “I  don’t  know  what  1020,  1060,  or  10100  steel  means.”  

 

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Fe-­‐Fe3C  Phase  Diagram  Eutectoid  Reac;on-­‐  Steel  Review  

 α     γ   Fe3C  Ferrite   Austenite   Cemen-te  

Alpha  Iron   Gamma  Iron   Iron  Carbide  

BCC  Iron   FCC  Iron   Carbide  

BCC  Iron  with  inters--al  solid  solu-on  of  C  up  to  0.022  wt%  carbon  

FCC  iron  with  Inters--al  solid  solu-on  of    C  up  to  2.14  wt.  %  C    

A  hard  and  briAle  stoichiometric  (fixed  composi-on)  compound,  Fe3C.  It  has  an  orthorhombic  crystal  structure.  

 For  1030  steel  at  1000°C      1)  Phases  present:  

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

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Given  1)  1000°C    2)  1030  Steel    

Co  

X

Cγ    

Wγ    

Co  

0.3%  

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 For  1030  steel  at  850°C      1)  Phases  present:  

Co  Cα Cγ  

Wα= Q  P+Q  

Cγ-­‐Co  Cγ-­‐Cα

Wγ= P  P+Q  

Co-­‐Cα  Cγ-­‐Cα

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  850°C    2)  1030  Steel    

1  0   Co   Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature   850  

α    

α    +Fe3C  

Fe3C  +γ    

Cα Cγ  

Q  P  

0.3%  

X

Fe3C  

727°C  

0.45%  0.01%  

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 For  1030  steel  at  728°C      1)  Phases  present:  

Co  Cα Cγ  

Wα= R  S+R  

Cγ-­‐Co  Cγ-­‐Cα

Wγ= S  S+R  

Co-­‐Cα  Cγ-­‐Cα

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  728°C    2)  1030  Steel    

1  0   Co   Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

α    

α    +Fe3C  

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Cα Cγ  

R  S  

0.3%  

X

0.022  %  

0.76%

Fe3C  

727°C  

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 For  1030  steel  at  726°C      1)  Phases  present:  

Co  Cα CFe3c  

Wα= U  T+U  

CFe3c-­‐Co  CFe3c-­‐Cα

WFe3= T  

T+U  Co-­‐Cα  CFe3c-­‐Cα

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  726°C    2)  1030  Steel    

1  0   Co   Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

γ  

α    

α    +Fe3C  

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Cα CFe3C  

U  T  

0.3%  

Fe3C  

X0.022%  727°C  

0.022  %  

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 For  1076  steel  at  728°C      1)  Phases  present:  

Co  

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  728°C    2)  1076  Steel    

1  0  Co  

Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

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0.76%  

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XCγ  

Wγ    

727°C  

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 For  1076  steel  at  726°C      1)  Phases  present:  

Co  Cα CFe3c  

Wα= U  T+U  

CFe3c-­‐Co  CFe3c-­‐Cα

WFe3= T  

T+U  Co-­‐Cα  CFe3c-­‐Cα

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  726°C    2)  1076  Steel    

1  0   Co  Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

γ  

α    

α    +Fe3C  

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Cα CFe3C  

U  T  

0.76%  

Fe3C  

X0.022%  

727°C  

0.022%  

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 For  10100  steel  at  728°C      1)  Phases  present:  

Co  

CFe3c  

V  W+V  

CFe3c-­‐Co  CFe3c-­‐Cγ  

WFe3c= W  W+V  

Co-­‐Cγ    CFe3c-­‐Cγ  

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  78°C    2)  10100  Steel    

1  0  Co  

Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

γ  

α    

α    +Fe3C  

Fe3C  +γ    

CFe3C  

V  W  

1%  

Fe3C  

X

0.022%  

727°C  Cγ  

Wγ  =  

Cγ  0.76%  

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 For  10100  steel  at  726°C      1)  Phases  present:  

Co  Cα CFe3c  

Wα= Y  Z+Y  

CFe3c-­‐Co  CFe3c-­‐Cα

WFe3= Z  Z+Y  

Co-­‐Cα  CFe3c-­‐Cα

Phase  Calcula;ons  

3)  Phase  wt.  frac.  (0  a1)  of  each  ph.:  

2)  Chemical  comp  of  each  phase:  

6.67  

Given  1)  726°C    2)  10100  Steel    

1  0  Co  1%  Composi;on-­‐  Wt%  C    

1000  

800  

600  

400  

Tempe

rature  

γ  

α    

α    +Fe3C  

Fe3C  +γ    

Cα CFe3C  

Y  Z  

Fe3C  

X0.022%  

727°C  

0.022%  

Muddiest  Points      Phase  Diagrams  IV:  Fe-­‐Fe3C  Phase  Diagram  Calcula;ons  

 Muddiest  Points:    •     “In  a  two  phase  region  how  can  composi;on  be  determined  by  looking  to  either  side  of    the    two-­‐phase  region?”  

•     “Where  do  you  get  the  numbers  from  on  the  phase  diagram  to  do  the  calcula;on?”  

•  “I'm  s;ll  a  liGle  unclear  on  how  to  calculate  the  frac;on  of  each  phase”  

•  “I  don’t  know  what  1020,  1060,  or  10100  steel  means.”