Mg-9Gd-3.5Y-2Zn-0.5Zr合金材料喷丸强化工艺及摩擦磨损性能研究OA北大核心CSTPCD

As an indispensable industrial structural element,magnesium plays a very important role.In current practical applications,compared with other alloys,magnesium alloy has a low density and a lighter structure,and has been applied in many fields such as automobiles,electronics,medical treatment,and military weapons.Rare earth magnesium alloys generally refer to magnesium alloys containing rare earth elements.The comprehensive mechanical properties of magnesium alloys can be further improved by adding zirconium,aluminum,zinc,rare earth and other elements to pure magnesium,combined with appropriate processing technology.Magnesium alloy is the lightest metal structural material in engineering applications,which has the advantages of high specific stiffness,high specific strength and easy recovery.However,magnesium alloys have the problem of poor wear resistance,which makes them fail in the wear process and shortens their service life,thus limiting the potential development of magnesium alloys.In order to overcome this problem,it is particularly important to study and improve the wear resistance of magnesium alloys.Shot peening is an important mechanical surface treatment technology,which can obtain nanocrystals by hardening or strengthening the surface,improve the wear resistance of materials,and is one of the effective ways to reduce the fatigue of parts and improve the life of parts.Compared with other mechanical surface treatment methods,the equipment is simple and low-cost and is not limited by the shape and position of the workpiece,with convenient operation.Secondly,the controllable plastic deformation can be effectively achieved by shot peening parameters. In this study,the surface of Mg-9Gd-3.5Y-2Zn-0.5Zr alloy was treated by shot peening process,and nano-strengthened layer was prepared on the surface of the alloy,and then dry sliding friction and wear experiments were carried out to explore the change of wear resistance of the alloy after shot peening.OM and SEM were used to study the changes of grain size and structure characteristics from the surface to the inside of the alloy,the mass loss before and after the friction and wear test was measured by electronic balance,the hardness distribution in the depth direction of the strengthened layer of the alloy was measured by Vickers microhardness tester,and the morphology characteristics of the alloy after friction and wear were studied by SEM,and the wear mechanism was explored. The results showed that after the surface peening of Mg-9Gd-3.5Y-2Zn-0.5Zr alloy,grain refining layers of about 200 to 370 μm appeared on the surface,in which the peening pressure was 0.4 MPa,the time was 40 s,the fine grain strengthening layer was about 250 μm,and the hardness was about 155HV.Compared with that of the original sample,the hardness was improved by about 50％,and the strengthening effect was the best.After shot peening,the surface of magnesium alloy has plastic deformation and nanocrystals are obtained.The grain size gradually increases from the surface to the inside,showing a gradient change.After shot peening,the wear quality of the sample is generally reduced,and the wear resistance is improved.The wear resistance of the sample is the best when the pressure is 0.4 MPa and the shot peening time is 40 s.In the friction-wear of as-cast samples,abrasive wear and adhesive wear play a major role.After the shot peening process,the wear mechanism changes.When the shot peening time is 60 s,the oxidation wear plays a leading role.In addition,with the increase of shot peening pressure,fatigue wear gradually changes from an auxiliary role to a leading role.