The non-stochiometric ordering phenomena of Cu-Zn-Al shape memory alloy having 1.3-1.5 electron concentration was studied theoretically by using Inden's advanced Bragg-William-Gorski(BWG) model of LRO (long range ordering) theory.
The ordering temperatures of B2 and DO3, $T_{B2}$ and $T_{DO3}$ were calculated with the alloy composition having constant electron concentration 1.48.
Composition dependence of martensitic transformation temperature was interpreted theoretically.
It was shown that the variation of martensitic transformation temperature when aged at low temperature come from the variation of order parameter of austenite ($\beta_1$).
Poly-crystalline alloy having the composition of 77.5 w/o Cu-14.2 w/o Zn-8.5 w/o Al was studied experimentally in this work.
Deposition of stable phase α, $\gamma_2$ from the metastable β phase was analyzed by microhardness test and X-ray, and those results were applied to the life expectancy of shape memory effect.
The tensile test was performed for poly-crystalline specimen and the results were compared with those of single X-tal specimen which had been performed in this laboratory in last year.
The fracture-mode was intergranular fracture although the SEM investigation of fracture surface showed the formation of micro-void coalescence, i.e., dimple. And, the dimple size was inversely proportional to holding time at 850℃.
The maximum shape memory strain was 4-5%, elongation at room temperature was 6% and intergranular fracture strength was 45 Ksi. The intergranular fracture strength was independent on the tensile test temperature.
