Structure of mechanically alloyed Ti-Al-Nb powders

Ti-Al-Nb ternary powder mixtures containing 24Al-11Nb, 25Al-25Nb, 37.5Al-12.5Nb, and 28.5Al-23.9Nb (at. pct) were mechanically alloyed in a SPEX 8000 mixer mill using a ball-to-powder weight ratio of 10:1. The structural evolution in these alloys was investigated by X-ray diffraction and transmission electron microscopy techniques. A solid solution of Al and Nb in Ti was formed at an early stage of milling, followed by the B2/body-centered cubic (bec) and amorphous phases at longer milling times. The stability of these phases and their transformation to other phases have been investigated by heat treating these powders at different temperatures. The B2/bcc phase transformed into an orthorhombic (O-Ti₂AlNb) or a mixture of the orthorhombic (O) and hexagonal close-packed (α₂-Ti₃Al) phases, the proportion of phases being dependent on the powder composition. Milling beyond the amorphous phase formation resulted in the formation of an fee phase in all the powders, which appears to be TiN, formed as a result of contamination of the powder. Formerly Graduate Student, University of Idaho     

The Beta Titanium Alloys

The beta titanium alloys offer many advantages in terms of processing, mechanical properties, and low cost of fabricated components compared to conventional titanium alloys. However, in the past, melting difficulties, reproducibility problems, and the conservatism of designers resulted in only one major application—on the SR-71 “Blackbird,” Mach 3+ surveillance airplane. This paper discusses the characteristics of the beta titanium alloys— from melting, through processing, to final microstructure and mechanical properties— and suggests that with recent advances the time is now ripe for the titanium community to successfully fend off competition from other materials by making increased use of this alloy class.*     

Titanium Aluminides: Science, Technology, Applications and Synthesis by Mechanical Alloying

The production. characteristics. and commercialization of monolithic and composite titanium aluminides are summanzed with emphasis on use in the demanding aerospace industry. The attractive elevated temperature properties combined with alow density make these materials of great interest, but inherently low "forgiveness", and environmental concerns, must be overcome before widespread use will occur One synthesis method for the production of monolithic titanium aluminides-mechanical alloying- will be discussed in detail     

Developments in the synthesis of lightweight metals

Because of their low density, alloys of aluminum, magnesium, titanium, and intermetallic compounds such as titanium, and intermetallic compounds such as titanium aluminide are particularly attractive for aerospace applications. This article describes various methods of synthesizing and processing lightweight metals with enhanced physical properties.