Research On Mechanical Properties And Tribological Behaviors Of TiZr-based Alloy Subjected To Severe Plastic Deformation

Titanium and titanium alloys are widely used in the aerospace, marine chemical,bio-medical, automotive industries and other fields because of their excellentcomprehensive mechanical properties. By employing the combination of severe plasticdeformation (SPD) and heat treatment, we realize the modification of microstructure andmechanical properties of TiZrAlV alloy. Then, we conduct mechanical and friction andwear tests of TiZrAlV alloy by using Instron5948Micro Tester and GTM-3M ball-on-disctribometer (against GCr15steel ball), respectively. Finally, we explore the evolution lawbetween the microstructure and mechanical properties and investigate the influence ofmicrostructure and friction experiment parameters on TiZrAlV alloy tribologicalproperties by using XRD, OM, TEM and SEM analysis techniques.The test results show that by the SPD combined with675C/10min+625C/2h+300C/1.5h heat treatment we successfully prepared a hierarchical and multi-phase (i.e.comprised with microscale β phase matrix, micro-and submicroscale α lamellae,nanoscale needle-liked α martensite together with micro-and submicroscale α grains)microstructured TiZrAlV alloy with excellent combination of high yield strength (s~1438MPa), high ductility (εf~7.65%), and good fracture toughness (KIC~57MPa m1/2). Bycomparing different stran conditions we also find that both the strength, ductility andfracture toughness of TiZrAlV alloy are simultaneously enhanced with the increasing ofrolling strain.Friction and wear tests on TiZrAlV alloy after SPD and heat treatment are furthercarried out using a ball-on disc scheme. The tribological behaviors of TiZrAlV alloy underdifferent heat treatments and friction test conditions are quite different. In vacuum, thespecimen suffered from675C/10min+625C/2h+300C/1.5h heat treatment presentsan excellent wear-resistant characteristics. This is related to surface hardening due to thefriction heat and surface temperature gradient, which induced the formation of hardsecondary α martensite, during the dry friction and wear tests. The wear-resistance ofTiZrAlV alloy in vacuum is better than in atmosphere. The wear mechanisms inatmosphere are mainly oxidative wear, abrasive wear and delamination wear. While in vacuum are typical adhesive wear. In vacuum condition, the friction coefficient betweenTiZrAlV alloy and GCr15is decreased with the increase of applied loads and specimenrotation velocity together with its fluctuation. However, the wear volume is increased asthe applied loads and specimen rotation velocity increasing.