Cementite Dissolution in Cold Drawn Pearlitic Steel Wires: Role of Dislocations

Abstract

Despite numerous investigations in the past, mechanism of cementite dissolution has still remained a matter of debate. The present work investigates cementite dissolution during cold wire drawing of pearlitic steel (~ 0.8wt% carbon) at medium drawing strain (up to true strain 1.4) and the role of dislocations in the ferrite matrix on the dissolution process. Quantitative phase analysis using x-ray diffraction (XRD) confirms more than 50% dissolution of cementite phase at drawing strain ~ 1.4. Detail analysis of the broadening of ferrite diffraction lines confirms presence of strain anisotropy in ferrite due to high density of dislocations (~ 1015m-2) at drawing strain 1.4. The results of the analysis shows that the screw dislocations near the ferrite-cementite interface are predominantly responsible for pulling the carbon atoms out of the cementite phase leading to its dissolution.

X-ray Diffraction Analysis of Severely Cold Deformed Hypereutectoid Steel Wire

“…XRD analysis has been done on Cu 3-7 , ferritic-pearlitic steel 8 , Aluminium 9-10 martensitic steel [11][12] , pearlitic steel [13][14][15] , nickle 16 ,FeN 17 , 10Cr-5W heat resistant steels 18 . The elaborate study on elastic constants 19 for hypereutectoid steel and dislocations contrast factors [20][21][22] of cubic crystals is available in literature.…”

A microstructure-based constitutive model for pearlite.

“…It can be seen that the microstructure becomes more homogeneous as the carbon starts to be released from the cementite plates. Chakraborty et al [44] observed by means of X-ray diffraction (XRD) that cementite lamellae dissolves a 50% at a drawing strain of 1.4. The mechanism proposed by the authors involves the screw dislocations in the cementite interfaces playing a dominant role, so that these dislocations are responsible to pull the carbon out of the cementite.…”