The poor surface performance of titanium alloys substantially limits their application in many fields, such as the petrochemical industry. To overcome this weakness, the Cu and Ni double layers were deposited on the surface of TC4 alloy by the electroplating method, and the isothermal diffusion process was performed at 700 °C to enhance the binding ability between Cu and Ni layers. The isothermal diffusion behavior and microstructure of the coating were systematically analyzed, and tribological property and corrosion resistance of the coating were also evaluated to reveal the influence of isothermal diffusion on the surface performance. It was shown that multiple diffusion layers appeared on the Cu/Ni and Ni/Ti interface, and that NixTiy and CuxTiy phases were formed in the coating with the increase of diffusion time. More importantly, Kirkendall diffusion occurred when the diffusion time increased, which led to the formation of continuous microvoids and cracks in the diffusion layer, weakening the surface performance of the Cu/Ni coatings. This paper unveils the relationship between the microstructure of the Cu/Ni coatings and isothermal diffusion behavior, providing guidelines in preparing high performance surface coatings.

The effects of the process parameters on the deformation behavior of Ti14 alloy have been investigated by compressive tests, at temperature between 1000°C and 1150°C and with strain rates from 5×10-3 S-1 to 5S-1. The results revealed that deformation temperature and strain rate have significant effect on the peak flow stress, the flow stress decreases. The response time required by deformation was affected by the strain rates and liquid fraction was done by the temperature. At higher temperature, transforms deformation mechanism was changed from sliding between solid particles to flow of liquid incorporating solid particles by the change of the liquid fraction.

The feasibility of forging of AL-1050 alloy of cylindrical heatsink under warm conditions is demonstrated in the present work. The stress-strain curves and friction factor play an important role in the cylindrical heatsink forging. The purpose of forging lubrication is to reduce friction between blank and die, and to decrease resistance of metal flow to die. The stress-strain curves at different temperatures are obtained by compressing tests. The friction factor between 1050 aluminum alloy and die material are determined at different temperatures by ring compression tests with graphite lubricants. The compressing and ring compressing tests are carried out by using the computerized screw universal testing machine. The finite element method is used to investigate the forming characters of the forging process. To verify the prediction of FEM simulation in the cylindrical heatsink forging process, the experimental parameters such as stress-strain curves and fiction factor, are as the input data during analysis. Maximum forging load and effective stress distribution are determined of the heatsink forging, using the finite element analysis. Finally, the cylindrical heatsink parts are formed by the forging machine under the conditions using finite element analysis.

The influence of hydrogenation on microstructure and tensile properties of Ti40 alloy has been investigated. The microstructure observation reveals that a new phase called η phase with FCC structure appears at the grainboundaries when the hydrogen content above 0.3 wt.%. With increasing hydrogen contents, the strength first increases and then decreases, and the ductility decreases as the specimens tensioned at both room temperature and 700oC. These phenomenons are resulted from the solution strengthening of hydrogen addition in Ti40 alloy with single β phase. As the hydrogen content increases, the fracture mode changes from dimple to cleavage fracture for specimens tensioned at room temperature. When tested at 700oC, the morphology of fracture surfaces in the specimens are all characterized by polygonal grains and the fractograph exhibits typically “sugar candy” brittle fracture for the specimen with 0.5wt% H.