Quantitative evaluations of improved surface integrity in ultrasonic rolling process for selective laser melted in-situ TiB₂/Al composite

The novel surface nano-crystallization ultrasonic rolling process (USRP) technology is used to improve the surface integrity of Al-based TiB₂/Al composite and widen potential applicability in this work. Based on self-developed two generations of USRP devices, the basic attempts to processing parameters are conducted to qualitatively link up with the surface integrity indicators of roughness, hardness and residual compressive stress as well as the surface morphologies. G factor based on energy conservation criterion is proposed to quantitatively evaluate USRP strengthening effect on the surface integrity. What is more important is that it can standardize the processing parameters with different generations USRP facilities. The logarithmic responses of surface integrity indicators with regard to the G factor show that significant strengthening effectiveness is able to be produced by two-side USRP (TS-USRP) with less energy consumption, as compared to single-side USRP (SS-USRP). The effect of strengthening efficiency is also included from the determinations of W_p and W_r factors, which are the selection criterion on optimized processing parameters. The results show that TS-USRP specimens possess generally better comprehensive performance than SS-USRP do, and TS-2 (F = 120 N, v = 4 mm/s, d = 0.1 mm, n = 3) is the best-choice specimen among them. In addition, the potential strengthen mechanisms are further explored for this specimen based on advanced microstructural observations, where remarkable compaction of the printing powder and the crushing of original inclusions play an important role in it. This work provides an insight into how to provide a direct quantitative evaluation on strengthening effect, which is expected to promote in many processing and manufacturing fields.