# Investigation of CuTi Alloy for Applications as Non-Sparking Material
## 2 Materials and Methods  
Within the analysis method using ThermoCalc, (2024a--2024.1.132110-498) several thermodynamic calculations of the Cu-Ti system were performed, which were confirmed by the results presented in the specialized literature [5; 12]. All stable phases were considered, as well as the very high solubility of TiCu\({}_{4}\) and CuTi compounds, and complete thermodynamic modeling of the system was conducted (Figure 1a), confirming the results obtained by [PERSON] et al. using CALPHAD [13]. The legend in Figure 1a shows all the possibilities suggested by the ThermoCalc program and the temperature conditions under which they can be formed, considering first the mole fraction of Ti. Cu-Ti alloys were obtained by melting pure Cu and high-purity Ti (99.99%) in an electric furnace at 1100 \({}^{\circ}\)C. The alloys were labeled as Cu\({}_{2}\)Ti (chemical composition: Cu: \(\sim\)98 wt%; Ti: \(\sim\)2 wt%) and Cu\({}_{3}\)Ti (chemical composition: Cu: \(\sim\)98 wt%; Ti: \(\sim\)3 wt%). The ingots (10 mm in diameter and 100 mm in length) were hot-rolled using an electrical resistance laboratory furnace for heating and rolling equipment. It is expected that the experimental alloy (Cu \(\sim\) 3 wt% Ti) will contain the phases Cu + \(\beta\)-TiCu\({}_{4}\) in the as-cast condition. The resulting strips were 3 mm thick and 160 mm long. No longitudinal cracks were observed, and the integrity of the material was not affected by the thermomechanical processing. After hot rolling, the materials were heat treated by quenching with water + ice to obtain an aging heat treatment. Figure 1: ThermoCalc diagrams for the CuTi system (**a**) diagram of the compounds formed in the Cu-Ti system as a function of the temperature variation and the Ti mole fraction from 0 to 1, (**b**) activity variation of the components of the Cu-4 wt% system Ti as a function of Ti mass percentage, (**c**) enthalpy variation of the Cu-4 wt%Ti system as a function of Ti mass percentage, and (**d**) Gibbs free energy variation of the Cu-4 wt%Ti system as a function of Ti mass percentage. Cast and hot-rolled Cu-Ti plate samples were used to determine various surface properties using a cert-Umt2 tribometer [14; 15]. The test specimens were of lamellar shape with 2 parallel surfaces (dimensions 50 \(\times\) 20 \(\times\) 2 mm). The samples used for the scratch tests had a polished surface and were subjected to an increasing force from 1 to 25 N during the test. Microstructural analysis was performed by optical microscopy with a Zeiss optical microscope with a MotiCam optical camera at room temperature (\(\approx\)25 \({}^{\circ}\)C). For microstructural analysis, the samples were ground with SiC paper ut to 2400 grit and mechanically polished using an aqueous alumina slurry (1-0.3 \(\upmu\)m). The etching was performed with an aqueous solution of iron chloride (FeCl\({}_{3}\)) for 10 s [16]. Scanning Electron Microscope (SEM) VegaTescan LMH II analyses were performed for microstructural analysis, defect analysis of the obtained materials and analysis of the surface condition of the alloys after the wear resistance tests, after the corrosion resistance tests and after the mechanical property tests [17]. Following the development of the experimental alloys and the electro-corrosion tests, the alloys were investigated for their chemical composition. Microstructural analysis was performed after preparing the surfaces of the experimental samples (by grinding and polishing). The VoltaLab 21 electrochemical system (PGP201-Economic Potentiostat, VoltaLab, Rochdale, UK) equipped with a 3-electrode cell and a VoltaMaster 4 data acquisition and processing software was used to analyze the (electro-chemical) corrosion resistance by linear and cyclic potentiometry tests, the samples being as-cast and hot-rolled. The samples with an area of 5 mm\({}^{2}\) were mechanically polished and washed with distilled water before the experiment.