Investigation of the machinability of Nİ-Tİ shape memory alloy with silicon reinforcement in wire edm

In this study, the structural and wire erosion machinability properties of samples produced by adding silicon to Ni-Ti shape memory alloy were investigated. Samples were prepared to contain 1%, 2% and 3% silicon. They were produced in ingot form using the arc melting method. To obtain the desired crystal lattice structure, the samples were subjected to heat treatment at 870 °C for 24 hours and then cooled in ice water. XRD analyses were performed to examine the crystal structure. When measured at room temperature, all samples were found to be in the austenite phase. As the Si addition ratio increased, the Si signal intensity increased regularly throughout the entire analysis area; however, no localised intensity increases indicating accumulation, island formation, or Si-rich secondary phases were observed in specific regions. This indicates that Si atoms dissolved in the Ni-Ti matrix and that the alloy exhibited a chemically uniform structure. EDX analyses were performed on point measurements taken from different regions, and It was determined that characteristic peaks belonging to the Si element were clearly visible in the samples with Si addition and that the Si content showed a regular increase trend as the addition ratio increased. Elemental mapping analyses, performed to examine the elemental distribution of the samples at the microstructural scale, showed that the Ni, Ti, and Si elements were distributed homogeneously across the entire sample surface. When evaluating the cutting width in terms of kerf, the silicon content was determined to be the most dominant parameter at 79.18% according to the ANOVA results. For surface roughness, the silicon content was determined to be the most effective parameter with a contribution rate of 73.30%. Here, the silicon value reduced the Ra value up to 2%, but increased it again when added in higher proportions. In this context, adding up to 2% silicon to the alloy will be effective on Ra. The most suitable kerf value was determined to be 246 µ at a dielectric bar pressure of 14 bar, wire feed of 10 m/min, and time off of 200 μs for the sample containing 2% silicon. The most suitable Ra values were again determined to be 2.34 µm for the sample containing 2% silicon at a time off of 200 μs, a dielectric bar pressure of 14 bar, and a wire feed of 10 m/min.