| Title |
Point Defects and Ordering of Heat - Treated NiAl Alloys ( Ⅰ ) |
| Authors |
박희섭(Hee Sub Park) ; 고홍석(Hong Seok Ko) ; 홍경태(Kyung Tae Hong) ; 이경섭(Kyung Sub Lee) |
| Abstract |
The thermal vacancy concentration and the long range ordering have been studied using density measurement and X-ray diffractometry in stoichiometric NiAl NiAl is well known for large amounts of vacancies in thermal equilibrium even at room temperature. The thermal defects can be formed on heating and readily retained by quenching, and then can be annealed out by annealing treatment. Density measurement revealed that the amounts of annealed-out vacancies decreased and the difference in density between as-quenched and annealed NiAl also decreased with the repeated heating-quenching-annealing cycles. The density of NiAl single crystal increased by up to 1.8% just by repeated heating-quenching-annealing cycles. The intensity of a superlattice line relative to that of a fundamental line in heat treated NiAl increased. This means that it is possibile for the thermal vacancy concentration in NiAl not only to depend on the temperature but also to be related to long range ordering. |