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

Fei Li,Lixiang Yang,Xiao Zhang,Baode Sun,Yi Jiang,Chengkang Qi

doi:10.3390/app9081569

Fei Li, Lixiang Yang + Show 4 more

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https://doi.org/10.3390/app9081569

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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.

Highlights

On the basis of their low density, high modulus, high temperature strength, good flame retardancy, excellent oxidation resistance, and creep resistance, TiAl alloys have been developed into one of the most attractive materials for lightweight and heat-resistant structural parts, such as those used in aviation, aerospace, aeronautical missiles, automotive engines, and so on [1,2,3,4,5]
The low-toxicity gel casting system used was composed of N, N-dimethylformamide (DMF)
The scanning electron microscope (SEM) micrographs of the TiH2 and Al powders are shown in Figure 1a and Figure 1b, The SEM micrographs of the TiH2 and Al powders are shown in Figure 1a,b, respectively

Summary

Introduction

On the basis of their low density, high modulus, high temperature strength, good flame retardancy, excellent oxidation resistance, and creep resistance, TiAl alloys have been developed into one of the most attractive materials for lightweight and heat-resistant structural parts, such as those used in aviation, aerospace, aeronautical missiles, automotive engines, and so on [1,2,3,4,5]. There has been great interest in porous TiAl alloys as potential engineering materials for various industrial fields [6,7,8,9]. As a near net shaping technology, was firstly developed by Janney and Omatete in the early 1990s and has been widely applied in the ceramic industry [15,16,17,18]. In such a process, a high-solid-loading slurry consisting of raw powders, solvent, and organic binder is first required

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