PSI - Issue 23

Václav Paidar / Procedia Structural Integrity 23 (2019) 402–406

405

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

4

Fig. 1. Schematic phase diagram for a pair of Hexagonal and BCC elements (Hel and Bel) containing an intermetallic phase. LB line lies at the top of intermetallic phase, H denotes the point with the largest concentration of BCC solid solution on the hexagonal side and B on the BCC transition metal side, T c is critical temperature.

Table 2.Parameters of binary alloys.  T m (X-Zr) is the difference between melting temperatures of transition metal elements and zirconium (2128 K),  T im is the difference between the higher melting temperature and upper temperature of the intermetallic phase,  T up is the difference between the upper temperature of BCC miscibility gap and the monotectoid temperature where the hexagonal phase appears,  c and  c s are the widths of composition gaps in atomic per cents,  is the efficiency of separation. For two different upper temperatures of two parts of the miscibility gap, three values of  T up are listed: lower, medium and higher one.

Zr-X

 T m (X-Zr)

 T im 

 c 

 T up

 c s



Zr-Nb Zr-Mo Zr-Ta

614 768

368 977 980

73 43 84 13

269 650 823 953

743

31

812

1142

1165 1567

Zr-W

1212

67

876

1087

1297

Table 3.Parameters of binary alloys.  T m (X-Hf) is the difference between melting temperatures of transition metal elements and hafnium (2504 K),  T up is the difference between the upper temperature of BCC miscibility gap and the monotectoid temperature where the hexagonal phase appears,  c and  c s are the widths of composition gaps in atomic per cents. Againthree values of  T up are listed: lower, medium and higher one, when the upper temperatures of the miscibility gap are different.

Hf-X

 T m (X-Hf)

 T im

 c

 T up

 c s



Hf-Mo Hf-Ta

392 789

453

14

700

835 102 631

970

26 281

41

42

Hf-W

1191

910

35

349

912

28 495

The efficiencies for element separation in selected refractory high-entropy alloys obtained according to eq. (1) for both types of binary phase diagrams with zirconium and hafnium are in a good agreement with concentration differences shown in Table 1. The strongest separation tendency is found for tungsten in both binary phase diagrams with zirconium and hafnium.