Precise Measurements of Thermophysical Properties of Liquid Ti–6Al–4V (Ti64) Alloy On Board the International Space Station

Abstract

The titanium alloy Ti–6Al–4V (Ti64) is a very widely applied alloy with extreme importance in the fields of aerospace, automotive, and biomedicine. For a large range of manufacturing methods that involve the liquid phase, such as casting, metal injection molding, thermal spraying, and additive manufacturing, process simulations are an important tool for the optimization and development of the fabrication process. Reliable thermophysical property data of Ti64 in the solid and the liquid phase are necessary inputs to such models. Due to the high melt reactivity of titanium alloys with container materials, measurements performed using conventional thermophysical equipment are usually impossible. Precise benchmark measurement of thermophysical properties (surface tension, viscosity, specific heat, total hemispherical emissivity, thermal conductivity, electrical resistivity, mass density) of Ti64 is presented in the undercooled liquid phase using containerless electromagnetic levitation on board the International Space Station (ISS). The obtained values are compared with predictive models that can help to analyze the data for other compositions of the alloy system. The property values are applied to simulations of industrial fabrication processes, to optimize these processes and thus the product quality.