The dynamic recrystallization mechanism of ultrasonic power on non-contact ultrasonic-assisted direct laser deposited alloy steel

Advances in Ultrasonic-Assisted Directed Energy Deposition (DED) for Metal Additive Manufacturing

“…As early as the 1800s, researchers began experimenting with adding vibrations to enhance metallurgical bonding, refining grains in castings, and altering solidification structures [94]. In recent years, UA-DED has emerged as a promising technique to actively control the printing process for better microstructural and mechanical properties [95][96][97].…”

“…UA-DED integrates high-frequency mechanical oscillations into the deposition process, engendering a spectrum of enhancements across the microstructure, densification, and mechanical integrity of AM parts. The oscillations and induced acoustic streaming perturb the thermal profiles and flow dynamics during solidification to directly influence grain evolution, porosity formation and defect generation [44,95,106,107]. By regulating the melt pool hydrodynamics and energetics, these distinct improvements across the grain morphology, density, defects, and various mechanical properties highlight the capabilities of ultrasonic assistance in augmenting directed energy deposition processing, properties, and performance capabilities beyond conventional limitations.…”

The Grain Size Evolution Mechanism of A517Q Alloy Steel Fabricated by Laser and Wire Additive Manufacturing Assisted with Different Ultrasonic Vibration Treatments

“…The subgrains will be recrystallized under continuous ultrasonic energy treatment, forming a quantity of fine grains with small dislocation differences, thus refining the grains. [26] The grain orientation spread (GOS) value less than 1 is considered to be recrystallization. [38] As shown in Figure 7e, compared with the sample without UV, the proportion of GOS value less than 1 in the samples with dual UV increased from 6.5% to 15.4%.…”

“…The subgrains will be recrystallized under continuous ultrasonic energy treatment, forming a quantity of fine grains with small dislocation differences, thus refining the grains. [ 26 ]…”

“…Moreover, UV can promote the transition from columnar grains to equiaxed grains by increasing the cooling rate and refining the grain size of the deposition layer. Zhou et al [ 26 ] investigated the dynamic recrystallization (DRX) behavior of the noncontact ultrasonic‐assisted process in direct laser‐deposited alloy steel. The application of ultrasonic increases the microscopic plastic deformation inside the deposition layer and provides energy for DRX.…”