||This study is to investigate the Ti-Cu-Ni and Ti-Ag-Pd 800oC isothermal phase diagram. Both the diffusion couple and the equilibrated alloys methods are applied to determine the equilibrium phase diagrams. |
In this experiment, the specimens were prepared by an electric arc furnace. then seal in a vacuum quartz tube, after high temperature heat treatment and metallurgical treatment, using electronic micro-finder (EPMA) to analysis the equilibrium phase composition.
There are ten three-phase equilibrium In Ti-Cu-Ni 800oC equilibrium phase diagram, as follows (1) βTi-Ti2Cu-Ti2Ni, (2) Ti2Cu-Ti2Ni-TiNi, (3) Ti2Cu-TiCu- TiNi, (4) TiNi-T2-T1, (5) TiCu-TiNi-Ti3Cu4, (6) TiNi-Ti3Cu4-T1, (7) Ti3Cu4-Ti2Cu3-T1, (8) T2- T1-TiNi3, (9) T1- T4- (Ni, Cu), and (10) T1- βTiCu4 - (Ni, Cu). Besides, the Ti2Ni-TiNi-T1 three-phase equilibrium found in Ti-Cu-Ni diffusion couple experiment and this was a metastable equilibrium according to the results of the equilibrated alloy experiments.
In the Ti-Ag-Pd system, it is difficult to discuss the diffusion path since the extremely different diffusion rate between Ti/Ag and Ti/Pd. We found that Ti and Pd preferentially reacts to form intermetallic phases, and the intermetallic phases of Ti-Ag are difficult to form. Also, there has another problem that Ag segregation in the alloy preparation by using Arc-melter. There is only Ti-rich part of the phase diagram as two three phase equilibrium αTi-PdTi3-PdTi2 and βPdTi-Pd3Ti2-αPd2Ti determined in Ti-Ag-Pd phase diagram, Ag solubility in PdTi3 Phase is 5.62 at.%, Ag solubility in PdTi2 Phase is 13.47 at.%, Ag solubility in αPd2Ti Phase is 6.70 at.%.