Effect of martensite content, its dispersion, and epitaxial ferrite content on Bauschinger behaviour of dual phase steel

Abstract

Dual phase microstructures were produced in a low carbon steel, in which the martensite volume fraction was kept constant at two levels, of 18 and 25%, while the epitaxial ferrite content was varied independently. The microstructures were produced with two dispersions of martensite, a relatively coarse dispersion by intercritical annealing of a ferrite/pearlite starting microstructure and a ® ner dispersion from an initial martensitic microstructure. Bauschinger tests were conducted using prestrains in both tension and compression of 0 . 4, 1, and 2 . 2%. Prestrain direction had no measurable effect on plastic ¯ow behaviour after strain reversal. Mean back stresses increased with increasing strain and martensite content, and were higher for the ® ner martensite dispersion. They decreased signi® cantly with increasing epitaxial ferrite content in the case of the ® ner dispersion, but less signi® cantly in the coarser dispersion. These effects of microstructure are discussed in terms of stress transfer to martensite, work hardening, and tensile properties. It is concluded that about half of the mean back stress developed during early plastic deformation was generated by stress transfer to the martensite, the remainder arising from strain hardening of the matrix. A small permanent softening in the Bauschinger test resulted from a reduction of effective stress in the ferrite matrix when the strain path was reversed.MST/4990

Electrochemical corrosion response of a low carbon heat treated steel in a NaCl solution

“…It is well known that the great challenge in engineering applications is the improvement of a property without provoking deleterious effects in another property. Experimental evidences have shown that both mechanical and electrochemical corrosion behaviors are strongly dependent on the resulting microstructural arrangement [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…A continuous yielding, low yield strength (0.2% proof stress), high tensile strength, high and uniform elongation are intrinsic and attractive mechanical properties of DP steel reported since the 1970s [5,6]. Recently, some studies have focused on mechanical and abrasive wear properties of DP steels as a function of heat treatment cycles [6,[12][13][14][15].…”

Influence of Martensite Mechanical Properties on Failure Mode and Ductility of Dual-Phase Steels

“…It is well known that the macroscopic mechanical behavior of DP steels depends on various factors, such as the grain size of the ferrite and the volume fraction, morphology, and carbon content of the martensite phase. [4][5][6][7][8][9][10][11] The fine grain size, high strength and volume fraction of the martensite phase generally increase the tensile strength of DP steels. On the other hand, a high volume fraction of the martensite phase reduces the ductility of DP steels.…”

The hardenability of austenite with different alloy content and dispersion in dual-phase steels

“…The effect of varying heat treatment temperature, time, alloy content, and cooling rate on the decomposition product has been intensively studied by several investigators (Lawson et al, 1981;Eldis, 1979;Matlock et al, 1979;Lawson et al, 1980;Jeong and Kim, 1985;Marder, 1977;Geib et al, 1980;Mould and Skena, 1977;Rigsbee and Vander Arend, 1977;Huppi et al, 1980;Erdogan and Priestner, 1999;Erdogan and Priestner, 2002;Erdogan, 2002;Sarwar and Priestner, 1999;Priestner and Ajmal, 1987;Erdogan, 2003). The austenite transformation following intercritical annealing is different from that after normal austenitisation in two respects.…”