Microstructural study of adiabatic shear bands formed in serrated chips during high-speed machining of hardened steel
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The characterization of the microstructure and phase transformation in adiabatic shear bands (ASBs) within the serrated chips generated during high-speed machining of hardened 30CrNi3MoV steel has been performed. The observations showed that the microstructure gradually changes from the center of the ASB to the matrix of the chip, the fine equiaxed grains appear with size of about 0.4–0.6 μm in the center of the ASBs, the transitional region adjacent to the ASB is characterized by the broken and elongated martensite laths in shear direction. The analysis indicated that the serrated chip formation was likely due to adiabatic shear instability that occurred in the primary shear zones and the transformation to martensite within the ASB. Dynamic recovery and recrystallization are the dominant metallurgical processes during microstructural evolution of ASB.
KeywordsMartensite Shear Band Martensite Lath Adiabatic Shear Adiabatic Shear Band
This research is supported by National Natural Science Foundation(50875033, 50775018), by the Natural Science Key Foundation of Tianjin (No.08JCZDJC18400),and by Tianjin Key Laboratory of High Speed Cutting & Precision Machining. The authors are grateful to Prof. Xu Yongbo for his contribution in the microscopic analysis.
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