Laser Processing of Titanium Aluminides

In the last few years there has been an enormous increase in research and development activity on titanium aluminides, in particular, on the Ti-Al compounds, since they have immense potential as new high-temperature lightweight structural materials. Based on their many attractive properties such as high melting point, low density, high modulus, high strength at elevated temperatures, titanium aluminides alloys have been identified as candidate materials for aerospace applications. Laser processing of materials has been developing since 1970s. It has been widely accepted by the industry that laser processing has several advantages over other material processing technologies in improved surface-related properties of materials. The advantages of laser processing are highly localized and low in-total heat input, which minimizes the distortion of the work piece, high density and concentrated energetic beam source, high production rates, greater flexibility and automatic control in the industrial applications.

Laser processing of a series of Ti-Al alloys including pure Ti and Ti-Al intermetallic compounds has been studied using Nd-YAG laser. SEM, XPS and XRD techniques were used to determine the surface morphological, chemical and compositional characteristics of the laser-processed samples. Analysis of the results showed that cracks along grain boundaries cause by rapid heating and cooling of laser processing were the dominant characteristics of the surface morphologies of the processed samples. The aluminum content of the Ti-Al alloys plays an important role in crack initiation and/or development. The severity of cracks increased with the increase in aluminum content of the alloys. XPS results indicated that the oxidation layer present on the processed samples consisted of adsorbed oxygen apart from Al2O3, TiO2 and TiO. In addition, the oxide film of TiAl alloy as well as the oxidation layers on Ti3Al intermetallic compound were enriched with aluminum.

Reference: Sherman McElroy, Dehua Yang and Ramana G. Reddy: “Laser Processing of Titanium Aluminides,” Journal of Materials Engineering and Performance, vol. 9, No.5, October, (2000), pp. 506-515.