Relation of normal load with test temperature at mild−severe wear transition state for Mg−Gd−Y−Zr alloy

The wear behavior and mild−severe(M−S)wear transition of Mg−10Gd−1.5Y−0.4Zr alloy were investigated within a temperature range of 20−200℃.The morphologies and compositions of worn surfaces were examined to identify the wear mechanisms using scanning electron microscope and energy dispersive X-ray spectrometer.The microstructure and hardness in the subsurfaces were analyzed to reveal the M−S wear transition mechanism.Under a constant loads of 20,35 and 40 N,each wear rate−test temperature curve presented a turning point which corresponded to the M−S wear transition.In mild wear,the surface material was plastically deformed and hence was strainhardened,whereas in severe wear,the surface material was dynamically recrystallized and consequently was softened.It has been found that the critical temperature for M−S wear transition decreases with increasing the normal load,and the normal load exhibits an almost linear relationship with critical temperature for M−S wear transition.This work reveals that the M−S wear transition of the studied alloy conforms to the surface DRX temperature criterion.

Correlation between test temperature, applied load and wear transition of Mg97Zn1Y2 alloy

Dry sliding wear tests were performed on Mg97 Zn1 Y2 alloy at various temperatures of 20,50,100,150 and 200°C using a pin-on-disc wear testing machine in order to reveal mild-severe(M-S)wear transition mechanism during elevated-temperature wear testing.It was shown that at each test temperature,the wear rate increased with increasing load,and all wear rate-load curves demonstrated two distinct stages i.e.mild and severe wear stages.The predominant wear mechanisms operating in mild and severe wear stages were analyzed,and they were indicated in the mild and severe wear regimes of a wear mechanism transition map,respectively.M-S wear transition mechanism was analyzed by comparison of microstructure transformation and hardness change in subsurfaces of samples tested in mild and severe wear stages,from which M-S wear transition mechanism was confirmed as softening of surface material arising from dynamic recrystallization(DRX)microstructure transformation.The M-S wear transition load was found to have a linear relationship with test temperature,and decreased with rising test temperature.M-S wear transition obeyed a critical surface DRX temperature(SDT)criterion under given conditions,and the transition loads were estimated at various test temperatures by using the criterion.

WEAR TRANSITIONS OF C/Cu COMPOSITE MATERIALS

An unlubricated sliding friction test on C/Cu composite materials is described. The result of the test proves that adhesive wear is the domination. At a certain speed, when the load upon the test block is light, the wear rate remains low level and the friction pair has a good antifriction performance. But when the load increases to a certain value, the wear transitions happen, the wear becomes severe.