Characterization of the interface heat transfer coefficient during non-isothermal bulk forming of Ti-6AL-4 V alloy

Abstract

An investigation on the interface heat transfer coefficient during bulk forming of glass-coated Ti-6Al-4 V was carried out. Heat transfer experiments were conducted where two dies were heated to various temperatures and Ti-6Al-4 V cylindrical specimen heated to 970 degrees C was upset tested. Temperature changes of the lower die consisting of AISI H13 were recorded in relation to the process variables such as reduction ratio, lubrication condition, and initial die temperature. The temperature change data were analysed to determine the interface heat transfer coefficients between lubricated die and glass-coated workpiece by using the plotting approach on calibration curves derived from analytical method and the inverse algorithm coupled to finite element (FE) analysis. The former was to determine the initial guessing values for applying the inverse algorithm. The validation of final coefficients determined by the inverse algorithm was made by comparison between the upsetting process and the FE analysis results.