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Delay Time in the Alpha to Gamma Transformation of Iron


Boedtker, Olaf Alexander (1961) Delay Time in the Alpha to Gamma Transformation of Iron. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z8WG-R830.


Iron, containing a certain amount of carbon and nitrogen, was pulse-heated from an initial temperature in the alpha phase into a final temperature within the gamma phase. The bulk of the allotropic transformation took place a certain time after the final temperature had been reached. The relationship between this delay time and the final temperature follows an Arrhenius type rate equation with a heat of activation of 20,500 ± 1400 cal per mole. It was also established that under the present experimental conditions alpha iron can be heated directly into the delta phase without going through the gamma phase. The effect of the rate of heating on the alpha to gamma transformation temperature can be deduced from the measurements of the delay time. An interpretation of a possible transformation mechanism is given. It is assumed that the transformation takes place in two steps: (1) A relatively slow diffusion-like growth of nuclei of the new phase in the old matrix to their critical size, followed by (2) a very, fast shear transformation.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Mechanical Engineering and Physics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Minor Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Duwez, Pol E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1961
Record Number:CaltechETD:etd-03172006-110102
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:983
Deposited By: Imported from ETD-db
Deposited On:17 Mar 2006
Last Modified:10 Nov 2023 23:17

Thesis Files

PDF (Boedtker_oa_1961.pdf) - Final Version
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