Mechanisms of nanostructure and metastable phase formations in the surface melted layers of a HCPEB-treated D2 steel

Zou, Jianxin; Grosdidier, Thierry; Zhang, Kemin; Chen, Dong

doi:10.1016/j.actamat.2006.05.053

Cited by 139 publications

(115 citation statements)

References 36 publications

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“…These results are very different from the one recently obtained for an initially textured FeAl intermetallic alloy treated by HCPEB. [15] In this case, the combination of the thermal effect with the shock wave induced dynamic recrystallization, which, in turn, generated strong texture modifications and reduction of grain size by the formation of subgrains.…”

Section: Discussionmentioning

confidence: 98%

“…Indeed, assuming that all the solute elements are redistributed in the melt, the M s temperature estimated from various formulas developed for steels by Nehrenberg, [21] Andrews, [22] or other authors [23] always gave M s values lower than 60 K. Another factor that must have contributed to the inhibition of the martensitic transformation is the ultra-fine size of the austenite domains formed in this melted layer by the rapid solidification process. [24,25] Indeed, it is well established that the triggering of the martensitic transformation depends on the chemistry as well as on the local microstructural features that may (1) act as nucleation sites (deformation bands, dislocation distribution heterogeneities) or, on the contrary, (2) inhibit its formation by constraining effects (fine grain size). [26][27][28][29] The presence of this metastable homogeneous c layer formed by the HCPEB treatment at the top surface is very important for potential applications.…”

Section: Discussionmentioning

confidence: 99%

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Texture and Microstructure at the Surface of an AISI D2 Steel Treated by High Current Pulsed Electron Beam

Zou

Grosdidier

Bolle

et al. 2007

Metall Mater Trans A

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Surface modifications were investigated for an AISI D2 steel after 25 pulses of high current pulsed electron beam (HCPEB) treatment. In particular, X-ray diffraction (XRD) was used to determine the thickness, nature of phase, and texture in the top surface melted layer. The mechanisms responsible for the structure and texture evolutions were further asserted by scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD) results. Under the action of the beam, the large carbides present in the steel were melted and dissolved so that the top surface rapidly solidified as a 3-lm-thick layer of ultra-fine-grained metastable austenite without any martensite formation. The growth of the c phase led to an unusual <100> + <110> fiber solidification texture. In addition, R3-twin boundaries were observed to bridge, most often, near <110> domains. These features, observed here in a Fe supersaturated and highly undercooled melt, are discussed in light of recent findings on atypical growth in directionally solidified Al-based alloys. [40][41][42] Comparatively, the a phase present in the heataffected zone remained randomly oriented.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Texture and Microstructure at the Surface of an AISI D2 Steel Treated by High Current Pulsed Electron Beam

Zou

Grosdidier

Bolle

et al. 2007

Metall Mater Trans A

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“…Because of the large differences of heat conductivity between the tungsten carbides and the Co binder, voids were generated by the different shrinkage during the rapid solidification. The formation of craters was a result of the sublayer melt eruption as discussed elsewhere [24]. Considering the surface simulations in Figure 8, there were liquid and graphite in the surface melt at ~3200 K according to the ternary phase diagram [25], and this composite would be kept down under a rapid cooling rate of 1.26 × 10 8 K/s.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Nanostructure and Metastable Phases at the Surface of a HCPEB-Treated WC-6% Co Hard Alloy with Increasing Irradiation Pulse Numbers

Zhang

Hao

et al. 2017

Coatings

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This work investigates the mechanisms of the microstructure evolution in the melted surface layers of a WC-6% Co hard alloy when increasing the number of pulses of irradiation by high-current pulsed electron beam (HCPEB) treatment. After one pulse of irradiation, about 50% of the stable hcp WC phase was melted and resolidified into the metastable fcc form (WC 1−x ). When increasing the numbers of pulse irradiation, the WC phase decomposed into ultrafine-grained WC 1−x plus nanosized graphite under our selected energy condition. Because of the rapidity of HCPEB carried under vacuum, the formation of the brittle W 2 C phase was avoided. In the initial Co-rich areas, where the Co was evaporated, melting and solidification led to the formation of nanostructures Co 3 W 9 C 4 and Co 3 W 3 C. The volume fraction of the nano domains containing WC 1−x , Co 3 W 9 C 4 , and Co 3 W 3 C phases reached its maximum after 20 pulses of irradiation. The improved properties after 20 pulses are therefore due to the presence of nano graphite that served as lubricant and dramatically decreased the friction coefficient, while the ultrafine-grained carbides and the nano domains contribute to the improvement of the surface microhardness and wear resistance.

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“…Besides, stress waves, shock waves, vibration and other physical phenomena can also be induced on the material surface, which results in extraordinary modification effects, such as improved strength, microhardness, wear resistance and corrosion resistant properties [9][10][11] . Therefore, by using HCPEB surface modification techniques, many researchers had studied the surface strengthening and surface alloying of steels, magnesium alloys, aluminium alloys, etc 11 .…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Liquid Phase Separation of CuCr Alloys Treated by High Current Pulsed Electron Beam

Zhou

Chai

et al. 2015

Mat. Res.

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Mechanisms of nanostructure and metastable phase formations in the surface melted layers of a HCPEB-treated D2 steel

Cited by 139 publications

References 36 publications

Texture and Microstructure at the Surface of an AISI D2 Steel Treated by High Current Pulsed Electron Beam

Texture and Microstructure at the Surface of an AISI D2 Steel Treated by High Current Pulsed Electron Beam

Evolution of Nanostructure and Metastable Phases at the Surface of a HCPEB-Treated WC-6% Co Hard Alloy with Increasing Irradiation Pulse Numbers

Microstructure and Liquid Phase Separation of CuCr Alloys Treated by High Current Pulsed Electron Beam

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