Search

Abstract: In order to improve the surface mechanical properties of GB-5083 aluminum alloy, titanium–aluminum–nitrogen thermo-reactive diffusion coatings were fabricated on the surface of Al substrate through deposition and nitriding process. The substrates were firstly deposited with pure Ti film by magnetron sputtering and then plasma nitrided in an atmosphere of 40% N2–60% H2 at 460°C. The as-obtained coatings under different nitriding time were characterized by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), microhardness tester, scratch tester and pin-on-disc tribometer. Results showed that the multiphase coating comprising two sub-layers (i.e. the outside TiN0.3 layer, and the inside Al18Ti2Mg3 layer) can be obtained. The coating thickness increased slightly with increasing nitriding time. The hardness of the as-obtained coating has reached about 600HV, which is much higher than that of the GB-5083 Al substrate. The critical load of adhesive failure for the coating obtained by 16h nitriding reached 13N. Compared with the untreated Al alloy, the wear rate of the coated sample decreased 65% after 24h nitriding treatment. The analysis of worn surfaces indicated that the coated GB-5083 Al alloy exhibited predominant abrasive wear, whereas the uncoated one showed severe adhesive wear. [Copyright &y& Elsevier]

Highlights: [•] A novel duplex surface treatment on 2024 Al alloy was proposed. [•] A multiphase layer composed of TiN0.3, Al3Ti and Al18Ti2Mg3 was prepared on the surface of 2024 Al alloy. [•] The microstructures of TiN0.3, Al3Ti and Al18Ti2Mg3 were characterized by SEM and TEM. [•] The surface hardness of the multiphase layer reached to 590 HV0.01, five times harder than 2024 Al alloy. [•] The wear resistance of 2024 Al alloy was improved significantly. [ABSTRACT FROM AUTHOR]

Abstract: By means of magnetron sputtering method, pure Ti film with thickness of 1.25 μm was deposited on the surface of 5083 Al alloy specimens. The specimens were heated by ion bombardment in a plasma nitriding unit employing a mixed gas of N2 and H2 at 460 °C for 16 h. The treated surface layers of specimens were characterized by using SEM equipped with EDS, TEM, XRD analysis and nanoindentation as well as potentiodynamic polarization tests. The results show that the Al18Ti2Mg3 layer with a thickness of 6.3 μm can be formed on the surface of the specimens during interdiffusing of Ti, Mg and Al across the interface between Ti film and the substrate alloy. The interdiffusion layer possesses much higher Young's modulus (131 GPa), the nanohardness (8.97 GPa) and corrosion potential (−0.75VSCE) than those of 5083 Al–Mg alloy. Additionally, the Al18Ti2Mg3 phase layer has an excellent plastic deformation ability resulting mainly from its plasticity deformation power dissipation ratio (η p) up to 87%. [Copyright &y& Elsevier]

Aluminum-Copper alloys are widely utilized in military, aerospace and aircraft industries for its light weight, excellent castability, superior corrosion resistance, as well as high specific strength after solution, quenching and age hardening treatments. However, the distortion occurring in the quenching process limits its application, especially for the large scale complicated workpieces. In this study, a novel duplex treatment combining the coating and nitriding is applied to the sections of the thin-wall barrel that easy to deform during quenching. The results show that a gradient multiphase layer, consisting of two different regions, is shaped on the thin-wall sections easy to deform. The phase compositions of the surface and subsurface layer are dominated by TiN 0.3 and Al 3 Ti, respectively. The Young's modulus of the TiN 0.3 and Al 3 Ti are 199 GPa and 196 GPa respectively. While, the microhardness for both the two phases are 6.19 GPa and 4.24 GPa respectively, which are much higher than that for the aged ZL205A alloy substrate. The finite element method (FEM) simulation results show that the maximum temperature difference, thermal stress, residual stress as well as deformation of the thin-wall barrel workpiece are reduced due to the multiphase layer. Consequently, the maximum radial deformation of the workpiece can be reduced 96% due to the superior strength and hardness as well as heat conduction of the gradient multiphase layer. • Quenching deformation occurs on the thin-wall sections of the barrel according to the FEM simulation. • The gradient multiphase layer is prepared on the thin-wall sections by deposition titanium film and nitriding. • The phase composition of the multiphase layer is dominated by TiN 0.3 and Al 3 Ti. • The much higher heat conductivity and superior strength and hardness of the multiphase layer results in 96% reduction of the workpiece. [ABSTRACT FROM AUTHOR]