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  • Print publication year: 2008
  • Online publication date: June 2012

Chapter 11 - Martensitic Transformation

Summary

Introduction

In this chapter, we discuss one important means of altering the mechanical response of metals and ceramics: martensitic transformation. Martensitic transformation is a highly effective means of increasing the strength of steel. An annealed medium-carbon steel (such as AISI 1040) has a strength of approximately 100 MPa. By quenching (and producing martensite), the strength may be made to reach about 1 GPa, a tenfold increase. The ductility of the steel is, alas, decreased.

A quite different effect is observed in ceramics. Martensitic transformation can be exploited to enhance the toughness of some ceramics. If a ceramic undergoes a martensitic transformation during the application of a mechanical load, the propagation of cracks is inhibited. For example, partially stabilized zirconia has a fracture toughness of approximately 7 MPa m1/2. An equivalent ceramic not undergoing martensitic transformation would have a toughness less than or equal to 3 MPa m1/2.

An additional, and very important, effect associated with martensitic transformations is the “shape-memory effect.” Alloys undergoing this effect “remember” their shape prior to deformation. The three effects just described have important technological applications.

Structures and Morphologies of Martensite

Quenching has been known for over 3,000 years and is, up to this day, the single most effective mechanism known for strengthening steel. However, it is only fairly recently that the underlying mechanism has been studied in a scientific manner and understood.

Suggested Reading
J. W. Christian. “The Strength of Martensite,” in Strengthening Methods in Crystals, Kelly, A. and Nicholson, R. B., eds. Amsterdam: Elsevier, 1971, p. 261.
Christian, J. W.. The Theory of Transformations in Metals and Alloys, 2nd ed. Elmsford, NY: Pergamon Press, 1981.
Green, D. J., Hannink, R. H. J., and Swain, M. V.. Transformation Toughening of Ceramics. Boca Raton, FL, CRC, 1989.
A. H. Heuer. “Fracture-Tough Ceramics,” in Frontiers in Materials Technologies, Meyers, M. A. and Inal, O. T., eds. Amsterdam: Elsevier, 1985, p. 265.
Heuer, A. H., Lange, F. F., Swain, M. V., and Evans, A. G.. “Transformation Toughening: An Overview.” J. Am. Cer. Soc., 69 (1986) i–iv.
Krauss, G.. Principles of Heat Treatment of Steel. Metals Park, OH: ASM, 1980.
Nishiyama, Z.. Martensitic Transformation. New York, NY: Academic Press, 1978.
G. B. Olson and M. Cohen. “Principles of Martensitic Transformations,” in Frontiers in Materials Technologies, Meyers, M. A. and Inal, O. T., eds. Amsterdam: Elsevier, 1985, p. 43.
Olson, G. B. and Owen, W. S., eds., Martensite, Metals Park, OH: ASM, 1992.
Perkins, J., ed. Shape Memory Effects in Alloys. New York, NY: Plenum Press, 1975.
G. Thomas. “The Physical Metallurgy and Alloy Design of Dual Phase Steel,” in Frontiers in Materials Technologies, Meyers, M. A. and Inal, O. T., eds. Amsterdam: Elsevier, 1985, p. 89.