In order to obtain information on the diffusion mechanism in body-centered cubic transition metals, the pressure dependence of the diffusivity of 95Zr was measured in this equi-atomic alloy at 1003 or 1493K, using pressures of up to 1440MPa (table 306). The activation volumes at 1003 and 1493K were 0.31 and 0.35, respectively. These positive values conflicted with previously reported negative values, but agreed very well with the activation volume for self-diffusion in -Ti. Within experimental error, the activation volume was independent of the temperature, thus indicating that only 1 diffusion mechanism operated in spite of the markedly curved Arrhenius plots for 95Zr and 44Ti diffusion in this alloy. It was concluded that the present results confirmed the operation of a monovacancy mechanism in group-IVa body-centered cubic metals.

M.Büscher, C.Herzig, U.Köhler, H.Mehrer, W.Lojkowski: Physica Status Solidi B, 1992, 174[2], 347-57

Figure 50

Diffusion of H in (Ti,Zr)(Mn,V)(Fe,Co), (Ti,Zr)(Mn,V)(Fe,Ni) Alloys

(Squares: Ti0.1Zr0.9Mn0.9V0.1Fe0.5Ni0.5, circles: (Ti0.1Zr0.9)1.1Mn0.9V0.1Fe0.5Ni0.5,

triangles: Ti0.1Zr0.9Mn0.9V0.1Fe0.5Co0.5

 

Table 302

Chemical Diffusion Parameters for the Ti-Mo System

 

C (at%)

Do (m2/s)

E (kJ/mol)

10

227.0

207.2

20

81.3

194.5

30

100

192.5

40

44.0

185.2

50

31.0

179.1

60

33.0

177.5

70

19.0

168.9

80

4.9

148.7

90

9.2

152.8

 

 

Table 303

Diffusivity of Be in Ti60Ni40

 

Temperature (K)

D (m2/s)

604

8.5 x 10-22

612

1.3 x 10-21

619

1.9 x 10-21

632

4.3 x 10-21

633

5.9 x 10-21

642

7.5 x 10-21

653

2.0 x 10-20

666

3.7 x 10-20

667

4.2 x 10-20

690

1.5 x 10-19