Vacancy flux or supersaturation enhanced grain-boundary mobility, but experimental evidence was not large and in many cases the role of vacancies was only inferred indirectly. The importance of the role of the vacancy in grain-boundary mobility in commercially pure and high-purity Mg was showed effectively here by using mechanical spectroscopy, electrical resistivity and positron annihilation spectroscopy. It was found that the mobility decrease of grain boundaries and dislocations was related to vacancy concentration reduction attained after the homogenization treatment. Indeed, the largest vacancy concentration reduction was observed between 420 and 500K. Unlocking grain boundaries and dislocations required new vacancies, generated at above 500K. In addition, a new damping peak related to vacancies was discovered at 490K for an oscillating frequency of 1Hz.

The Role of Vacancies in the Mobility of Dislocations and Grain Boundaries in Magnesium. O.A.Lambri, M.Massot, W.Riehemann, E.J.Lucioni, F.Plazaola, J.A.García: Physica Status Solidi A, 2007, 204[4], 1077-92

 

Table 8

Grain-Boundary Diffusion of 65Zn in Mg-Al Alloys

 

Al (wt%)

Temperature (K)

P (m3/s)

0

698a

1.85 x 10-18

0

698b

2.50 x 10-18

0

648a

7.51 x 10-19

0

648a,c

1.47 x 10-18

0

648b

1.05 x 10-18

0

648b,c

1.79 x 10-18

0

598a

6.89 x 10-19

0

598a,c

7.24 x 10-19

0

598a,c

4.78 x 10-19

0

598b

7.23 x 10-19

0

598b,c

7.56 x 10-19

0

598b,c

6.28 x 10-19

0

548a

2.07 x 10-19

0

548a,c

1.86 x 10-19

0

548b

1.75 x 10-19

0

498a

2.35 x 10-21

0

498b

1.47 x 10-20

1.77

648a,c

1.00 x 10-18

1.77

648b,c

1.06 x 10-18

1.77

598a,c

4.71 x 10-19

1.77

598b,c

4.64 x 10-19

1.77

569a,c

2.52 x 10-19

3.9

648a

1.16 x 10-18

3.9

648a,c

9.75 x 10-19

a: serial sectioning, b: residual activity, c: annealed in Ar

continued

 

Table 8 (continued)

Grain-Boundary Diffusion of 65Zn in Mg-Al Alloys

Al (wt%)

Temperature (K)

P (m3/s)

3.9

648b

1.82 x 10-18

3.9

648b,c

1.05 x 10-18

3.9

598a

6.44 x 10-19

3.9

598a,c

4.04 x 10-19

3.9

598b

6.24 x 10-19

3.9

598b,c

4.71 x 10-19

3.9

548a

2.70 x 10-19

3.9

548a,c

2.22 x 10-19

3.9

548b

3.24 x 10-19

3.9

548b,c

2.56 x 10-19

3.9

498a

1.17 x 10-21

3.9

498a,c

1.72 x 10-20

a: serial sectioning, b: residual activity, c: annealed in Ar