The surfaces of Ti6Al4V alloy EBW (Electron beam welding) were processed by CO2 laser quenching, and residual stresses of EBW were measured with X-ray stress tester X-350A. The mechanism of residual stress was analyzed, the effects of assistant gas and laser power and spot diameter on residual stresses in EBW of Ti6Al4V alloy is investigated. Experimental results show that residual stresses in EBW are increased obviously by CO2 laser quenching under the given laser parameters, which improve its mechanical performances.
The focusing system is very important for laser processing, especially for laser micro-processing, whose characteristics influence directly the quality of laser processing. A new optical system from the potive axicon and spherical lens combination is proposed in this paper to generate the diffraction-free beam. Only one axicon is needed in this system to produce the variable diffraction-free beam spot of micro order by changing the ordinary cheap spherical lenses. If such an optical system is used as the focusing system for laser micro-processing, the sensitivity to the workpieces' position would be zero and the adaptability to the flatness of the workpieces' surface could be enhanced. Moreover, such a system could adapt well to the different processing criterion by changing the ordinary spherical lenses and would also have potential application in the measurement field.
The influences of processing parameters on laser-induced shock waves in metal components are discussed and analyzed. The effects of different parameters of laser shock processing (LSP) on residual stress of aerospace aluminum alloy LC4 were investigated. LSP was performed by using an Nd: glass phosphate laser with 23 ns pulse width and up to ~45 J pulse energy at power densities above GW/mm-2. Special attention is paid to the residual stresses from laser shock processing. Modification of microstructure, surface morphology by laser shock processing is also discussed. Results to date indicate that laser shock processing has great potential as a means of improving the mechanical performance of components.
Titanium nitride films are deposited on AISI 304 steel with a hollow-cathode-discharge (HCD) ion-plating technique. The status of residual stresses in TiN thin film coated on AISI304 substrate by HCD is studied by x-ray diffraction stress analyzer. By analyzing morphology of the residual stress of TiN thin film at interface between TiN film and AISI 304 substrate, the adhering mechanism of TiN thin film is understood as follows: the mechanical interlocking had important contribution to the adhesion strength, the thermal stress is the major factor which resulting TiN thin film peeling off spontaneously. The results show that the value of thin film is -210MPa~-650Mpa, and the thermal stress is compressive, the intrinsic stress is tensile, origins of the residual stress are primarily discussed.
Laser shock forming(LSF) is a new forming technique of sheet metal by applying a compressive shock wave on the surface of metal sheet. The plastic deformation of TA2 titanium metal sheet is performed under single laser shocking perpendicularly with Nd:Glass laser developed in Jiangsu University. The residual stress state in the horizontal and diagonal direction of the foursquare specimen, as well as the residual stress state in the radial direction of the circular specimen, was investigated with X-ray stress analyzer. The residual stress state of laser shock forming specimen is unique to some extent by contrast with traditional punch forming, which is influenced by the specimen shape and the deformation rate. The experiment results show that residual stresses value of TA2 Titanium Sheet Metal in laser shock area are up to 100MPa.Square specimen is more difficult to be formed than circular specimen, and the press value of cave is the larger than the one of convex.