Adiabatic shear banding in AISI 1045 steel during high speed machining: Mechanisms of microstructural evolution

Critical cutting speed for onset of serrated chip flow in high speed machining

“…In this figure, the solid and hollow patterns indicate that the chips obtained from corresponding cutting experiments are continuous and serrated, respectively. Some other published experimental data [30,32,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] are also given in this figure to validate the criterion (9). It can be noticed from Fig.…”

“…It is found that this condition usually occurs when Pe is large [53]. The criterion (9) indicates that, once the ratio of the external loading to the thermal diffusion (Reynolds thermal number Pe) achieves a critical value that dominated by the material properties, the serrated chip flow occurs. This shows striking analogy to the turbulent flow which takes place as the ratio of external loading to the viscous diffusion (Reynolds number Re) is up to a critical value that determined by the fluid properties.…”

“…The mechanism for the onset of serrated chip flow has been extensively studied [7][8][9][10][11][12], and for most ductile metallic materials, the emergence of serrated chip flow is found be related to the thermoplastic shear instability occurred in the primary shear zone (PSZ) [8,9], which is often referred to the formation of adiabatic shear band [13][14][15][16]. And thus, considerable efforts have been carried out to focus on the adiabatic shear localization in the serrated chip formation process, and several classical theoretical models have been developed to predict the onset of serrated chip flow.…”

Microstructure and mechanism of adiabatic shear fracture during serrated chip formation of hard machining

“…The previous researches found that, during the cutting process of hardened steel, two main types of ASB were produced which are deformed band and transformed band. There were the severely broken martensite laths like dynamic recovery microstructure within the deformed bands, however, inside the transformed bands, a large number of equiaxed grains with very small diameter were found, the dynamic recrystallization and phase transformation took place (Duan et al, 2009;Duan and Zhang, 2012). In this study, the serrated chips with deformed bands and transformed bands also are observed.…”

Modelling of the Relationship of Adiabatic Shear and Cutting Conditions for Higher Cutting Speed Ranges

“…Huang et al [13] carried out the perturbation analysis of thermoviscoplastic instability in chip formation to establish the relation for the segment spacing which was obtained by multiplying the chip flow velocity by the characteristic time of instability. Duan and Zhang [14] presented an in-depth investigation into the formation mechanisms and microstructures of adiabatic shear bands (ASBs) in hardened AISI 1045 steel induced by HSM. A systematic analysis, both experimental and theoretical, showed that a low cutting speed leaded to deformed ASBs, and a high cutting speed resulted in transformed ASBs.…”