Max-Plank Institute for Iron Research (Düsseldorf, Germany):

Ch. Kirchlechner, e-mail: c.kirchlechner@mpie.de

S. Djaziri

Yujiao Li
M. Herbig

B. Grabowski

G. A. Nematollahi
S. Goto

R. Kirchbeim

J. Neugebauer

D. Raabe

G. Dehm

MPIE has investigated spontaneous formation of martensite from ultimately deformed pearlite nanostructure. Pearlite steel wire with its plate structure from cubic volumetric-centered ferrum and cementite (Fe₃C) is subjected to cold drawing and becomes thinner; its microstructure varies as well — it is getting more fi ne and, at the same time, gradual dissolution of the cementite phase occurs. This process is accompanied by rise of wire tensile strength up to 7,000 MPa which is the extremely high parameter close to the level of theoretical tensile strength. Atomic probe tomography has displayed release of carbon on the boundaries of grains and subgrains and its accumulation in pearlite with consequent oversaturation. Oversaturated ferrite acquires spontaneously tetragonal distorted crystal structure — a phanomena that is known for martensite as Zener order. As a result, the parallels between the classic martensite and steel wire deformed at the room temperature can be made.

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