Forging process on gamelan bar tin bronze Cu-25wt.Sn post casting deformation to changes in microstructure, density, hardness, and acoustic properties

摘要

Casting and forging are a method of formation to produce gamelan instruments.This study aims to determine the effect of forging deformation on the as-cast gamelan bar to changes in the microstructure, hardness, density, porosity, and acoustical properties of the gamelan instrument.The research material was tin bronze Cu-25wt.%Sn.The casting process uses a sand casting method with a pouring temperature of 1100 °C.The forging deformation process was done by reheating the as-cast gamelan bar at a temperature of 600 °C.The thickness of the as-cast gamelan bar is reduced by 30% after the forging deformation process.The observations on the as-cast gamelan bar show coarse microstructure with large grains, inclusions, and increased porosity.The forged gamelan bar shows finer microstructure, elongated grain, a lamellar, a phase like a plate, and decreased porosity.The hardness of forged gamelan bar increased by an average of 30.3% VHN, density increased by 9,56% and porosity decreased by 95% compared to the as-cast gamelan bar.Acoustic properties show an increase in the natural frequency between the as-cast gamelan bar and the forged gamelan bar are 712.5 Hz and 1058 Hz.