Titanium alloy (Ti-6Al-4V) is widely used in the aviation and aerospace industry because of its outstanding overall performance. However, due to its intrinsic characteristics of low thermal conductivity and low elastic modulus, a titanium alloy is difficult to machine, which is featured by the elevated temperature in the machining zone, severe tool wear, and poor surface finish of a machined part. Therefore, it is of a great significance to study the temperature of the tool/workpiece contact area in the milling process. In this study, the three heat sources in the machining zone are assumed spiral-line shaped. A closed-form model, similar to the milling force prediction model, is proposed to calculate the heat flux density and milling heat coefficients. Milling experiments are conducted to calibrate the milling heat coefficients. The results show that the heat flux density is approximately linearly increased with the increase of cutting thickness. A model for predicting the temperature in the machining zone is proposed and validated by experiments using semi-artificial thermocouples. The relative errors of experimental values and predictive values are within 10%. This study offers a guidance to determination of the temperature in the machining zone and optimization of the process parameters in machining processes.
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