Effects of Ultrasonic Surface Rolling Processing and Subsequent Recovery Treatment on the Wear Resistance of AZ91D Mg Alloy

Abstract

AZ91D Mg alloy was treated by ultrasonic surface rolling processing (USRP) and subsequent recovery treatment at different temperatures. The dry sliding friction test was performed to investigate the effects of USRP and subsequent recovery treatment on the wear resistance of AZ91D Mg alloy by a ball-on-plate tribometer. The microstructure, properties of plastic deformation layer and worn morphology were observed by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) analysis and microhardness tester. Results illustrate that the grains of AZ91D Mg alloy surface layer are refined to nanocrystallines. The maximum microhardness of the top surface of the USRP sample reaches 102.3 HV. When USRP samples are treated by recovery treatment at 150 °C, 200 °C and 250 °C, the microhardness of the top surface decreases to 90.68 HV, 79.29 HV and 75.06 HV, respectively. The friction coefficient (FC) and wear volume loss of the USRP-R-150 sample are the lowest among all the samples. The worn surface morphology of the USRP-R-150 sample is smoother than that of other samples, indicating that the wear resistance of AZ91D Mg alloy treated by USRP and recovery treatment at 150 °C is improved significantly.

Improving the Surface Friction and Corrosion Resistance of Magnesium Alloy AZ31 by Ion Implantation and Ultrasonic Rolling

“…Plastic flow occurred on the surface of the USRP specimen under the action of multidirectional force during ultrasonic rolling; thus, the "peaks" on the material surface flowed into the "valleys," significantly reducing the mechanical defects (scratches) of the original specimen. The addition of lubricating oil on the surface of the sample further reduced the friction between the ball of the processing head and the surface of the sample, and thus the ultrasonic surface-rolling treatment significantly reduced the surface roughness of the sample [28]. Further reduction of surface roughness after ion implantation may have been due to sputtering, etching, and diffusion processes under this implantation dose.…”

Ultrasonic Surface Rolling Process: Properties, Characterization, and Applications

“…They noted that since AZ31 is a HCP structure, the number of slip systems is limited, and it is also the cause of limited plastic deformation; however, other deformation mechanisms, namely, twins, were activated, which contributed to grain refinement. Zhao et al [68] have explored USRP on AZ91D Mg alloy to improve the wear resistance. They had used a static load of 240 N at 20 kHz.…”

Effect of Cold Rolling and Annealing on the Microstructure and Texture of Erbium Metal

“…Most rare earth metals have hexagonal close-packed (HCP) structure and fewer slip systems; therefore, the plastic deformation is very difficult because the rolling deformation process can easily cause stress concentration and lead to cracking [10,11]. There is a lot of research involving magnesium [12][13][14] and magnesium alloy [15,16], and titanium [17,18] and titanium alloy [19][20][21], but there are few studies on the deformation of rare earth metal. Huang P. [22] studied the effects of annealing temperatures on the hardness and microstructure of high-purity metal scandium metal after hot forging, and obtained the optimum annealing process of 725 • C × 0.5 h. Wang S. [23] studied the effect of annealing temperature on the microstructure of high-purity Er target under 80% deformation after hot rolling and obtained the optimum annealing process of 570 • C × 1 h. However, hot deformation process can easily lead to target oxidation, serious loss of raw materials, and worse surface quality.…”