Molding properties of titanium-based feedstock used in low-pressure powder injection molding

The moldability of titanium-based feedstocks used in low-pressure powder injection molding process was investigated using numerical simulation and real-scale injections. Feedstock characterization and injection were conducted using a feedstock formulated from a Ti-6Al-4 V powder and a low-viscosity binder system. The thermal characteristics of the feedstock, including the specific heat capacity and the thermal conductivity, were measured over a 20-120 degrees C temperature range, while rheological profiles were experimentally measured at 80, 90, and 100 degrees C to establish the constitutive equations to be implemented in the model. The mold filling stage of a complex shape part was numerically simulated using Autodesk Moldflow Synergy 2019. The predicted filling time and magnitude of powder segregation after an injection were validated using a laboratory injection press and thermogravimetric analysis. The melt front location and filling completion predicted by the numerical model at different short shots were in good agreement with the experimental observations, with relative differences below 9%. Moldflow was also used to identify the high shear rate zones experienced by the feedstock, in which a predicted segregation of 2 vol% was validated by experimental tests. A halo shape segregation pattern was determined as resulting from a solidified skin and/or a segregation band passing near the interface of the shear rate gradient. (C) 2020 Elsevier B.V. All rights reserved.