# Investigation of CuTi Alloy for Applications as Non-Sparking Material
## 3 Results and Discussions
### Structural, Chemical and Phase Analysis of Experimental CuTi Alloys  
Two types of TiCu\({}_{4}\) equilibrium phases appear in CuTi alloys--a stable and a metastable one. The \(\alpha\)-TiCu\({}_{4}\) phase can be transformed into the \(\beta\)-TiCu\({}_{4}\) phase after a long aging treatment (even at low temperatures). It is also possible to transform the \(\beta\) phase during cooling into the stable \(\alpha\) phase if low solidification/cooling temperatures are used [23; 24]. The analyses were performed on the Cu-3 (wt%)Ti alloy, labeled as Cu\({}_{3}\)Ti. In the specialized literature, eight intermetallic compounds (TiCu\({}_{4}\), TiCu\({}_{3}\), TiCu\({}_{2}\), Ti\({}_{2}\)Cu\({}_{3}\), Ti\({}_{3}\)Cu\({}_{4}\), CuTi, CuTi\({}_{2}\) and CuTi\({}_{3}\)) have been identified in the Cu-Ti system [13]. It should be emphasized that most of the previous studies were performed on Cu-Ti diffusion alloys. [PERSON] et al. obtained in their alloys four different types of intermetallic compounds, which were TiCu\({}_{4}\), Ti\({}_{3}\)Cu\({}_{4}\), CuTi and CuTi\({}_{2}\), from the Cu-Ti diffusion couple held for 5-40 min under 890 \({}^{\circ}\)C. They observed that the microhardness of the diffusion zone was 510-550 HV, which is much higher than that of pure Cu (72 HV) or pure Ti (220 HV) and attributed this increase to the formation of new intermetallic phases or compounds in addition to the solid solution of Cu with solubilized Ti in its structure [25]. Figure 2a,b show the X-ray diffraction (XRD) spectra obtained from the cast and hot-rolled Cu\({}_{3}\)Ti samples. Several characteristic peaks of Cu and of the solid solution formed by Cu with Ti (solubilized in the Cu matrix) were identified, as well as one characteristic peak each of the TiCu\({}_{4}\) and TiCu\({}_{3}\) compounds, the only compounds that can form for this chemical composition according to the phase diagrams, mass or enthalpy variation of formation. A low-intensity peak identified on the surface of the cast CuTi alloy was attributed to titanium dioxide [20]. The diffraction patterns of these areas in the hot-rolled samples indicate the appearance of periodic stresses in the crystal lattice that were induced by the coherent particles of intermetallic phases and by the structure re-ordering in the areas richer in titanium, a fact possible only by reaching the relevant chemical composition. The microstructure morphology of the cast alloys is a homogeneous dendritic type, illustrated in Figure 3a. By using a steel casting mold, improved homogenization of the alloy was achieved, resulting in a random distribution of titanium in the copper matrix. The microstructure is dominated by dendritic morphology. A large amount of equilibrium \(\beta\) phase can be observed in the structure, which can be related to the relatively low solidification rate. At the microscopic level (Figure 3c), as a result of the discontinuous transformation, the lamella of the equilibrium phase appears in the Cu\({}_{3}\)Ti alloy arranged alternately with the lamella of the solid solution. Figure 2: Characteristic XRD spectra of Cu\({}_{3}\)Ti alloy (**a**) cast state and (**b**) hot-rolled state (900 \({}^{\circ}\)C). The phase with more Ti is the one with a lower percentage and appears as a eutectic in the dendritic form as shown by the main element distribution (Figure 4a-d). Figure 4: Main element distribution (Cu and Ti) in the cast alloy: (**a**) the area selected for analysis, (**b**) the distribution of overlapping Cu and Ti elements, (**c**) the distribution of Cu and (**d**) the distribution of Ti. Figure 3: Optical microscopy analysis of Cu\({}_{3}\)Ti alloy: (**a**) cast, (**b**) rolled and electron microscopy, (**c**) cast and (**d**) rolled. Hot deformation of the alloys was performed on the as-cast state samples. Four to five deformation passes with reduced degrees (<10%) were conducted after heating the ingots at 900-950 \({}^{\circ}\)C for 10 min. As the deformation increased, the samples progressed from uniform to nonuniform deformation.