Microstructure evolution of medium carbon steel during heat-assisted 3D ultrasonic vibration-assisted turning.

• 3D ultrasonic vibration-assisted turning (3D-UVAT) method driven by two actuators is proposed. • A modified J-C model is used to simulate the turning process. • Microstructural evolution in heat-assisted 3D-UVAT is compared for simulation and experiment. • The effect of different turning conditions on microstructure and hardness is presented. Medium carbon steel is an excellent carbon structural steel, and is one of the most common materials for metal cutting. Little research has been done on the microstructural changes induced by thermal-force coupling. In this paper, a finite element simulation method based on the improved J-C model is used to predict the grain size, microstructure change depth and surface hardness of medium carbon steel surface induced by heat-assisted 3D-UVAT are studied. The numerical simulation results are compared with the experimental results, and the significant influence of turning conditions on them is analyzed. The results show that heat-assisted 3D-UVAT lowered the grain size of machined induced deformation zone. Numerical model foresees this case with a mean error of 9.4%. Microstructure and hardness measurements under different turning conditions show that the turning speed and feed rate contribute significantly to grain size and grain refinement layer depth in the area being machined. [ABSTRACT FROM AUTHOR]