Stretch-flangeability correlated with hardness distribution and strain-hardenability of constituent phases in dual- and complex-phase steels

Song, Eunji; Lee, Gunhee; Jeon, Hansol; Park, Bong June; Lee, Jung-Gu; Kim, Ju‐Young

doi:10.1016/j.msea.2021.141353

Cited by 14 publications

(11 citation statements)

References 23 publications

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“…It is generally believed that the size and content of the hard phase, the strength difference between the soft and hard phases, and the RA content are the keys to determining the HER [24][25][26][27]. In this study, the RA content in CH steel is small.…”

Section: Effect Of Annealing Temperature On Properties Of Ch Steelmentioning

confidence: 79%

Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Chu,

Zhou,

Liu

et al. 2024

Metals

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In recent years, with the continuous improvement in the requirements for automobile steel formability, complex phase steel with high formability (CH steel) has been widely used. In the present study, the microstructure of CH steel was regulated using the actual production process as a basis and annealing temperature as a variable, and the effects of annealing temperature on the microstructure, properties, and fracture behavior of CH steel were analyzed. As the annealing temperature increases, the ferrite content decreases from 36.3% to 0, the martensite content decreases from 49.3% to 8.8%, the bainite content increases from 11.9% to 87.1%, and the retained austenite content first increases and then decreases within the range of 2.5~5.1%. Consequently, the tensile strength shows a decreasing trend, the yield strength first decreases and then increases, and the total elongation and the hole expansion ratio first increase and then decrease. The deformation coordination of each phase gradually becomes better, and the voids and cracks in the tensile and hole expansion samples expand along the ferrite and martensite or martensite/austenite (M/A) island interface, transforming into the bainitic ferrite and martensite or M/A islands. The test steel’s best tensile and hole expansion properties occur at annealing temperatures of 940 °C.

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Section: Effect Of Annealing Temperature On Properties Of Ch Steelmentioning

confidence: 79%

Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Chu,

Zhou,

Liu

et al. 2024

Metals

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“…In general, the stretch-flangeability of TRIP-aided steel is mainly controlled by the micro-crack/void initiation on shear-punching [14,17,21,22,26,29,35,36] and the following crack growth and/or void connection on hole-expanding [13,35], which are related to the matrix structure, the retained austenite characteristics, and the ss/t value. As shown in Figure 1b, TBF steel had excellent stretch-flangeability compared to TPF and TAM steels, displaying high stretch-formability (Figure 1a).…”

Section: Relationship Between the Stretch-flangeability And Shear-pun...mentioning

confidence: 99%

“…• The first-generation AHSS: ferrite-martensite/bainite dual-phase (DP) [8][9][10][11][12][13][14], complex phase [12,13], TRIP-aided polygonal ferrite (TPF) [10,[15][16][17][18][19][20], and TRIP-aided annealed martensite (TAM) [21,22] steels • The second-generation AHSS: high manganese TWIP steel [23][24][25],…”

Section: Introductionmentioning

confidence: 99%

“…These AHSSs are characterized by excellent stretch-formability (maximum stretch height) [12,[15][16][17][18][21][22][23][26][27][28]34,36] and stretch-flangeability (hole expansion ratio) [8,[10][11][12][13][14][15]17,18,[20][21][22][23][24][25][26][27][29][30][31][32][33][35][36][37], as shown in Figure 1 [21,22,26], as well as good deep drawability (limiting drawing ratio) [16,18,23] and bendability (minimum bending radius) [12,15,18,19,21]. These cold formabi...…”

Section: Introductionmentioning

confidence: 99%

“…Figure13. SEM images of (a,e,i) overview, (b,f,j) low magnification at the shear section, and (c,g,k) low magnification at the break section of the cross-section of the shear-punched surface layer in TPF,…”

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confidence: 99%

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Evaluation of Shear-Punched Surface Layer Damage in Three Types of High-Strength TRIP-Aided Steel

Sugimoto,

Shioiri,

Kobayashi

2024

Metals

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The damage properties in the shear-punched surface layer, such as the strain-hardening increment, strain-induced martensite fraction, and initiated micro-crack/void characteristics at the shear and break sections, were experimentally evaluated to relate to the stretch-flangeability in three types of low-carbon high-strength TRIP-aided steel with different matrix structures. In addition, the surface layer damage properties were related to the mean normal stress developed on shear-punching and microstructural properties. The shear-punched surface damage of these steels was experimentally confirmed to be produced under the mean normal stress of negative to 0 MPa. TRIP-aided bainitic ferrite (TBF) steel had the smallest surface layer damage, featuring a significantly suppressed micro-crack/void initiation. This was due to the fine bainitic ferrite lath matrix structure, a low strength ratio of the second phase to the matrix structure, and the high mechanical stability of the retained austenite. On the other hand, the surface layer damage of TRIP-aided annealed martensite (TAM) steel was suppressed next to TBF steel and was smaller than that of TRIP-aided polygonal ferrite (TPF) steel. The surface layer damage was also characterized by a large plastic strain, a large amount of strain-induced martensite transformation, and a relatively suppressed micro-crack/void formation, which resulted from an annealed martensite matrix and a large quantity of retained austenite. The excellent stretch-flangeability of TBF steel might be caused by the suppressed micro-crack/void formation and high crack propagation/void connection resistance. The next high stretch-flangeability of TAM steel was associated with a small-sized micro-crack/void initiation and high crack growth/void connection resistance.

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Effect of Cr and isothermal holding temperature on microstructure and properties of complex phase steel with high formability (CH steel)

Chu

Gao

Chen

et al. 2022

J. Iron Steel Res. Int.

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Stretch-flangeability correlated with hardness distribution and strain-hardenability of constituent phases in dual- and complex-phase steels

Cited by 14 publications

References 23 publications

Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Evolution of Microstructure, Properties, and Fracture Behavior with Annealing Temperature in Complex Phase Steel with High Formability

Evaluation of Shear-Punched Surface Layer Damage in Three Types of High-Strength TRIP-Aided Steel

Effect of Cr and isothermal holding temperature on microstructure and properties of complex phase steel with high formability (CH steel)

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