Effects of thermal material properties on precision of transient temperatures in pulsed laser welding of Ti6Al4V alloy

Abstract

This study investigates the effect of temperature-dependent material properties on the precision of a simulation in pulsed laser beam welding of Ti6Al4V alloy. Ti6Al4V is one of the most extensively used titanium alloys. The precision in transient temperature distributions developed in the thermal modeling part of a sequentially coupled thermo-mechanical simulation is crucial to the end results of structural mechanics. The temperature profile obtained by a finite element model at two distinct locations is validated by experimental results using temperature-dependent material properties. Then, the effect of assuming constant room temperature values for thermal conductivity, specific heat, and density on the temperature distribution is studied at different welding speeds. Temperature distributions are unaffected by the constant density assumption. The constant thermal conductivity assumption underestimates the peak temperatures far from the weld region, whereas the constant specific heat assumption overestimates these temperatures. This effect becomes prominent at low welding speeds. The temperature profile when conductivity and specific heat are assumed to be constant is nearly similar to that in the case of constant conductivity when conductivity and specific heat are assumed constant. Therefore, conductivity is the dominant variable. The constant conductivity assumption also restricts the heat flow from the weld to the edge region, thus increasing the size of the weld pool. This effect also becomes increasingly prominent at low welding speeds.