Study On Multiphase Layer Produced By Deposition Titanium Film And Nitriding Of ZL205A Aluminum Alloy

The surface hardness and wear resistance of ZL205 A aluminum alloy are improved by the composite process of magnetron sputtering and post plasma nitriding.Firstly,the formation energy of the possible phase in the thermally diffuse process is calculated by the first principle,the diffusion coefficient is calculated as the auxiliary.After the duplex treatment,the multiphase layer was formed.The phase structure,morphology and composition of the titanium film and modified layer were analyzed by XRD,SEM and EDS,the hardness and the wear test were carried out.The results of the first-principles calculation show that there is a diffusion process between Ti and Al,and the diffusion coefficient of Ti is much larger than that of aluminum.The formation energy of Al3 Ti is the lowest in Ti-Al compounds and the formation energy of Ti N0.3 is larger than that of Al3 Ti,and the absolute value of it's binding energy is great.Ti N0.3 is more difficult to form,but is more stable.Thus,when the titanium film is thick,the multiphase layer with Ti N0.3 and Al3 Ti is formed,When the titanium film is thin,the layer is a single compound Al3 Ti layer.A layer of dense and uniformly distributed ?-Ti was successfully prepared by magnetron sputtering method,the as-deposited titanium films with(002)preffered plane.with the thickness of titanium film increasing,the preferential orientation of(002)crystal plane is more obvious.When titanium film is thicker,the multiphase layer structure is formed: the outermost is Ti N0.3,and the intermediate layer is Al3 Ti,with the the thicker film,the larger proportion of Ti N0.3.When titanium film is thin,there is only Al3 Ti.Ti N0.3 is also preferred in the(002)plane,and the preferential orientation is enhanced with the increase of the thickness of the titanium film,meanwhile,the grains become more refined and more uniformly distributed.The hardness of the ZL205 A aluminum alloy is obviously improved.The modified layer is up to HV411,the 4.2 times of the aluminum alloy after aging.The hardness of the modified layer is improved when existing(002)crystal orientation preferred orientation of Ti N0.3.Although the friction coefficient is larger,the wear rate is reduced.Compared with the sample after aging,the wear rate decreased by 11.84%,47.13% and 50.58% respectively after the duplex treatment.The wear mechanism of the modified layer is mainly abrasive wear,accompanied with oxidation wear.