Nanometer Lamellar Microstructure and Mechanical Properties of gamma-TiAl+alpha2-Ti3Al Based Alloys

Timur Khismatullin 

Institute for Metals Superplasticity Problems, Russian Academy of Science, Ufa, Russian Federation

Abstract

A decrease in lamellar spacing to nanometer thickness range (lambda~10 nm) is an effective way to increase strength properties of gamma-TiAl+alpha2-Ti3Al based alloys. For that water quenching from the alpha phase field followed by low temperature aging is usually used. However, this method does not allow a large volume of the material to be obtained. In addition, low aging temperatures result in non-equilibrium microstructural condition at temperatures of potential application (700-800 C). To overcome these deficiencies, specially designed Ti-43Al-(Nb,Mo,B) and Ti-45Al-(Nb,Mo,B) alloys containing the elements with a low diffusive mobility (Nb and Mo) were used in the present work. Lamellar microstructure with a lamellar spacing lambda~10 nm was produced in bulk workpieces of the alloys using annealing in the alpha phase field followed by air cooling and aging. Mechanical tensile tests of flat specimens were carried out at T=20, 600-800 C and a strain rate 10-3 s-1. The tests revealed that high ultimate strength (sigma>900 MPa) was retained up to temperature as high as 800 C and reasonable ductility (elongation>1%) was obtained at room temperature in both alloys. Thus, using conventional heat treatment fine lamellar microstructures (with d<50 micrometers) having the nanometer lamellar spacing (lambda~10 nm) were successfully produced in bulk cast alloys Ti-43Al-(Nb,Mo,B) and Ti-45Al-(Nb,Mo,B) that allowed the mechanical properties to be considerably improved.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium B, by Timur Khismatullin
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-19 13:06
Revised:   2009-06-07 00:44
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