EFFECT OF TEMPERATURE ON YIELDING IN SINGLE CRYSTALS OF THE HEXAGONAL Ag-Al INTERMETALLIC PHASE. Technical Report No. 1
Oriented single crystals of the intermediate hexagonal phase containing silver plus 33 at.% aluminum were tested in tension over a wide range of temperatures. Slip was observed to take place by the {0001} (1120) and {11OO} (1120) mechanisms; fracture took place across the {11OO} plane and twinning cccurred by the {1012} mechanism. Basal slip exhibited a strong yield point over the range frorn 77 to 450/sup o/K, the upper resolved shear stress having the exceptionally high value of 10.500 psi over this entire range of temperatures. The critical resolved shear stress for prisrnatic slip decreased from 48.000 psi at 4.3/sup o/K to 23.000 psi at 170/sup o/H (Region I) following which it decreased slowly to 21,500 psi at 475/sup o/K (Region II); frorn 475 to 575/sup o/ K (Region III), the critical resolved shear stress decreased precipitously to 2000 psi; and from 575 to 750/sup o/K (Region IV) it decreased less rapidly to a low value of about 500 psi. Prismatic slip in Region I was shown to be controlled by the thermally activated mechanism of nucleation and growth of kinks in dislccations lying in Peierls potential troughs. In Region II for prisrnatic slip, as well as for all of the observed region of basal slip where yield point phenomena were observed and over which the critical resolved shear stress for slip was insensitive to temperature. the critical resolved shear stress was shown to be deterrnined by short range ordering (or clustering). (auth)
- Research Organization:
- California. Univ., Berkeley. Materials Research Lab.
- DOE Contract Number:
- AT(11-1)-34
- NSA Number:
- NSA-15-003096
- OSTI ID:
- 4120909
- Report Number(s):
- TID-6794
- Country of Publication:
- United States
- Language:
- English
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