Abstract
High purity iron alloys containing molybdenum and carbon have been isothermally transformed in the range 600° to 900°C and the structures examined optically and in the electron microscope. The decomposition of the austenite commences at the grain boundaries forming two different ferrite/carbide morphologies. Predominantly, fine fibers of Mo2C, 300 to 500A diam, grow in association with ferrite and in contact with the austenite, forming characteristic nodules. Increasing the carbon content from 0.2 to 1.0 wt pct results in a change in structure during transformation from Mo2C fibers/ferrite to a typical coarse pearlite reaction. In addition, Mo2C nucleates repeatedly at the moving λ-α phase boundary to form sheets of particles about 200 to 400A apart, the individual acicular particles being about 50A diam in the early stages of precipitation.
Published Version
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