Research On Tribological Behaviors Of Tizr-based Alloys Under Different Circumstances

Owing to excellent combined properties,such as low density,high specific strength and attractive corrosion-resistant properties,newly-developed TiZr-based alloy can be potentially widely used in aerospace,nuclear industry,and naval vessel as engineering material.In order to meet the engineering demand,the TiZr-based alloys not only owned excellent mechanical properties,but the tribological behaviors should also be understood.In this study,Ti20Zr6.5Al4V（TZ0Z for short hereafter）crystalline alloy and Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 amorphous alloy,which belonged to TiZr-based alloys,were used as the objective to study their tribological behaviors in air,vacuum,and high temperature,under different normal loads and sliding velocities.Scanning electron microscopy was used to analyze the characteristics of the worn surface and cross section under different experimental condions.Transmission electron microscopy was also used to study the microstructure evolution of T20Z alloy’s worn surface.Combined these with coefficient of friction（COF）and wear rate,the wear mechanisms were revealed.The results showed that the variations of COF in air which was influenced by normal loads and sliding velocity was illustrated below:when the sliding velocity was 0.59 m/s,the COF decreased with the normal load,varied from 0.28 to 0.33,as the velocity was increased to 1.17 m/s,the COF was increased with the normal load,varied from 0.26 to0.34.The wear rate was increased with the normal load,while the wear rate decreased firstly and then increased with the sliding velocity.The dominant wear mechanisms was changed from abrasive wear to abrasive wear,adhesive wear and micro-crack with increasing the velocity under the lower normal load;while the normal load increased to 30N,the dominant wear mechanisms were severe abrasive wear,adhesive wear and delamination wear.The microstructure evolution was also led by the tribological process,and the results showed that it changed from high dislocation density was piled-up inαphase to being nanocrystalline.In vacuum,the COF was varied from 0.3 to 0.48.For a certain velocity,the COF and wear rate was increased with the normal load.When the normal load was fixed,the COF increased firstly to 0.78 m/s and then decreased,while the wear rate was increased with the velocity.Under the lower normal load,the wear mechanisms were almost same,while the wear mechanisms were changed from abrasive wear to severe abrasive wear,delamination wear,and plastic deformation when increasing the normal load to higher.With increasing the sliding velocity,the dominant wear mechanisms were also changed.The wear mechanisms changed from mild adhesive wear and severe abrasive wear to severe abrasive and delamination wear.High temperature tribological properties of T20Z alloy was also analyzed in this research.The results illustrated that the wear rate was increased with temperature increased firstly;when the temperature reached 473 K,it was decreased with increasing the temperature.The wear rate was lowest when the temperature was 673 K.At the same time,tribological properties of Zr₄₁Ti₁₄Cu_12.5Ni₁₀Be_22.5 amorphous alloy were tested.The results showed that the counterpart material had an effect on the tribological properties.The COF was lowest when TiZr-based amorphous alloys self-mated（0.13⁰.21）and highest when the counterpart was AISI 5120 steel.The wear rate was increased with increasing the normal load or sliding velocity.The dominant wear mechanisms were abrasive and adhesive wear.