Effect of ultrasonic surface rolling at low temperatures on surface layer microstructure and properties of HIP Ti-6Al-4V alloy

The main purpose of this paper was to investigate the effect of ultrasonic surface rolling at low temperatures (80 °C, 120 °C and 160 °C) on material surface layer microstructure and properties of HIP Ti-6Al-4V alloy. Some microscopic analysis methods (SEM, TEM, XRD and EDS) were used to characterize material surface-modified layer. The results indicated that the samples treated by ultrasonic surface rolling at low temperature experienced an obviously plastic deformation in material surface-modified layer, and accompanied by some refined grains and dense dislocations generation. Moreover surface microhardness (414 HV) and residual stress (− 491 MPa) of ultrasonic surface-rolled sample at 120 °C were also greatly improved compared to that (323 HV and − 235 MPa) of untreated sample. The fretting friction and wear properties of ultrasonic surface-rolled sample at different temperatures are tested in dry friction conditions. The steady-state CoF and wear volume loss of ultrasonic surface-rolled sample at 120 °C were significantly smaller than that of untreated sample. But they are still larger than the steady-state CoF and wear volume loss of ultrasonic surface-rolled sample at room temperature. This could be attributed to the absence of cold work strengthening, comparatively low surface microhardness and increase deformation mechanism in material surface layer caused by low temperature heating.