Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys.
Abstract
A Transmission Electron Microscopy (TEM) investigation of th bainite reaction in Titanium-X alloys has been completed. Particularly in a Ti-Chromium alloy, but also in other Ti-X systems, both the eutectoid alpha and the eutectoid intermetallic compound components of bainite have been shown to grow by means of the ledge mechanism. Unlike pearlite, the systems of ledges of the two eutectoid phases are physically independent. A theoretical treatment of the diffusional growth of two eutectoid phases has been made following an analysis due to Hillert but incorporating growth by the ledge mechanism and permitting independence of the growth of the two product phases. This analysis showed that, when the equilibrium proportions of the two precipitate phases develop, they can only grow at the same rate when h/lambda (h = ledge height and lambda = inter-ledge spacing) is the same on both. This situation does not appear to obtain in Ti-Cr bainite (when a correction is made for the non-equilibrium proportions of alpha and Ti-Cr2 formed) but does in pearlite because the ferrite and cementite phases share the same set of growth ledges. Hence a fundamental distinction has been established between the pearlite reaction and the microstructurally-defined bainite reaction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 31, 1987
- Accession Number
- ADA177261
Entities
People
- A. M. Dalley
- H. I. Aaronson
- H. J. Lee
- T. Furuhara
- Y. Mou
Organizations
- Carnegie Mellon University