Microstructure of Ultrafine Acicular Bainite and Mechanical Properties of 3Cr2MnNiMo Mold Steel during Austempering

Ren, Jia; Li, Changsheng; Tu, Xingyang; Shao, Zhibao

doi:10.1002/srin.202200151

Cited by 3 publications

(2 citation statements)

References 46 publications

(52 reference statements)

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“…Consistent with our observations, earlier researchers [15,40,44] reported that numerous bainitic ferrite-austenite interfaces reduced the mean free path for dislocation glide, hence leading to high strength. Similarly, the contribution of martensite to the strength was reported in earlier investigations [21,45,46].…”

Section: Experimental Findings and Discussionsupporting

confidence: 79%

“…As the term suggests, a stepped austempering process includes two stages of isothermal holding at different temperatures to exploit the advantages of both low-temperature and high-temperature austempering [18][19][20]. In case of a lowtemperature austempering, a benefit may be envisaged in terms of a larger driving force for austenite transformation due to greater under-cooling [21,22]. Owing to a higher driving force, CFB structure in a finer morphology with less austenite can be expected leading to higher strength levels.…”

Section: Introductionmentioning

confidence: 99%

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Influence of two-step austempering at different temperatures on mechanical and microstructural properties of AISI 9254 high silicon steel

Nalçaci

Baysun

Bahador

et al. 2023

Ironmaking & Steelmaking

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This study was undertaken to understand the effects of two-step austempering treatment on an AISI 9254 high silicon steel towards tailoring the properties as desired while simultaneously employing the benefits of high and low austempering temperatures. The samples were initially austenitized at 850°C for 20 min, followed by austempering in a salt bath at the temperatures of 250-270-290°Cfor 20 min during the first stage. Subsequently, a second stage austempering was carried out by raising the temperature of the salt bath to 300°C at an average heating rate of 0.5°C/min, and the samples were kept in the salt bath for achieving a total austempering time of 120 min including the heating time. A conventional single-stage austempering was also conducted for comparison purposes, in which the austenitization temperature, the austempering temperatures and total time (stage I and stage II, i.e. 120 min) were kept the same for the benchmark samples. In the characterization studies, tensile test, hardness test, XRD analysis, optical microscope and field emission-scanning electron microscope (FE-SEM) equipped with EBSD detector were utilized. The findings of this study indicated that lowering the austempering temperature resulted in refining the structure with a decrease in the amount of austenite. According to the carbon content analysis through XRD patterns, the two-step austempering processes appeared to have considerably increased the carbon content of the austenite irrespective of austempering temperature. The best ultimate tensile strength (U.T.S) of 2194 MPa was achieved in the conventionally austempered sample at the lowest temperature of 250°C, while the best yield strength (Y.S.) of 1753 MPa was reached in the stepped austempered sample initially at 250°C followed by 300°C. In general, two-step austempering process led to a higher yield strength while affecting the ultimate tensile strength and total elongation depending on the austempering temperature.

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