Effect of Mold Material and Solidification Conditions on Microstructural and Mechanical Properties of Directionally Solidified Sn-0.7Cu Alloy Developed Using Microwave Energy

Microwave processing offers multiple advantages over conventional methods, such as shorter processing time. In the present study, Sn-0.7Cu alloy was melted using microwave energy at 900 W and 2.45 GHz. The alloy was then directionally solidified under different solidification conditions and while using mold materials. Influences of microwave exposure time, solidification conditions, and mold materials were investigated in terms of microstructure development, elemental distribution, phase formation, and mechanical properties of the casts. Results showed formation of a Sn-rich phase (primary phase) and Cu-rich phase (eutectic phase) consisting of Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs). Graphite mold produced finer IMCs compared to alumina mold due to higher conductivity. A microstructure gradient was observed, while microwave irradiation was provided during solidification. The maximum ultimate tensile strength and hardness were found to be 44.69 +/- 6.62 MPa and 11.53 +/- 0.43 HV, corresponding to the graphite mold under higher heat extraction condition. Comparatively, elongation of the cast material decreased with increasing heat removal from the mold. The XRD analyses confirmed the presence of the Sn-rich phase and the intermetallic compounds Cu6Sn5 and Cu3Sn.