Time-temperature transformation behavior of Ti-24Al-11Nb

✍ Scribed by L.M. Hsiung; H.N.G. Wadley

• Book ID: 103952357
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 892 KB
• Volume: 192-193
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/0921-5093(94)03320-x

✦ Synopsis

The time-temperature transformation behavior of a rapidly solidified (RS) Ti-24Al-11Nb alloy has been studied between 450 and 850 "C using X-ray diffraction, electron diffraction, transmission electron microscopy and microindentation methods. A revised isothermal transformation path from the initial B2 to the final cz? structure has been proposed: B2 (Pmjm)-B19 (Pmma)-0' (Cmcm) -0' (Cmcm) -a2 (P6,/mmc). Age-hardening was found to accompany the B2 + 0' transitions. The hardness increased to a maximum value of about 5.4 GPa when the microstructure consisted of mostly 0' laths. Further aging resulted in a softening correlated with 0' coalescence and transformation to the a2 phase. The hardness decreased to a minimum value of about 2.6 GPa when the microstructure had evolved to an equiaxed a2 structure. The results reveal that the O'-a2 reaction becomes extremely slow, i.e. the 0' phase is kinetically stabilized, at temperatures below about 500 "C.