Study on the Fabrication of Porous TiAl Alloy via Non-Aqueous Gel Casting of a TiH2 and Al Powder Mixture

Abstract

A porous TiAl alloy with 23.78% porosity was successfully fabricated via a low-toxicity, non-aqueous gel casting method by using a titanium hydride (TiH2) and aluminum (Al) powder mixture as the raw material. The effects of dispersant content and solid loading on the rheological properties of the TiH2/Al slurries were studied systematically. It was found that all the slurries exhibited a typical shear-thinning behavior, which is favorable for the gel casting process. Three-point bending tests of the dried TiH2/Al green bodies were carried out, and the results showed that the flexural strength was raised from 28.86 to 62.36 MPa with increasing monomer (hydroxyethyl methacrylate, HEMA) content. In order to study the degreasing process and minimize the possible residual carbon and oxygen after sintering, TGA analysis was performed. The fracture morphology of the sintered TiAl alloy (1400 °C for 2 h) was studied by scanning electron microscope (SEM). Based on the X-ray diffraction (XRD) identification, the main phases of the sintered part were γ-TiAl, α2-Ti3Al, and a small amount of Al2Ti and Al3Ti.