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We present cross-correlation frequency-resolved optical gating (XFROG) measurements of supercontinuum pulses generated by using a photonic crystal fiber (PCF), and ultraviolet (UV) pulses generated by frequency doubling of infrared ultra-short pulses. Since supercontinuum pulses have broad spectra, XFROG measurement typically requires using an extremely thin nonlinear crystal which has a thickness of sub-ten microns. Instead of using such a thin crystal, we employed a relatively thick crystal which was mounted on a galvanometer in order to achieve a phase-matching over the whole spectral bandwidth of the supercontinuum pulses by a crystal-dithering technique. Experimental results of the retrieved phase and intensity were in fair agreement with the independently measured data.

The mechanism of localized corrosion and phase transformation of tube-to-tube sheet welds of hyper duplex stainless steel (HDSS) were investigated in acidified chloride environments. The HDSS tube-to-tube sheet welded with an Ar shielding gas without a filler metal, which increases the ferrite content, Cr 2 N and pitting resistance equivalent number (PREN) difference between the two phases, demonstrated the lower corrosion resistance than that with Ar shielding gas with a filler metal. The pitting corrosion of the weld metal (WM) in the HDSS tube-to-tube sheet welded using a pure Ar shielding gas with a filler metal occurred at the dendrite core (DC) that Cr and Mo were depleted and at the region adjacent to Mu phase that Mo and W were depleted. The localized corrosion was selectively initiated at the ¡-phase because the PREN value of the ¡-phase was much smaller than that of the £-phase, irrespective of the chemical compositions of the shielding, and the areas of the WM, heat affected zone (HAZ) and base metal (BM) (except for the WM in the HDSS tube-to-tube sheet welded using Ar with a filler metal).

To elucidate the effects of copper addition on the precipitation of chromium nitrides and the associated pitting corrosion of the hyper duplex stainless steels, a potentiodynamic test, a scanning electron microscope analysis and thermodynamic calculation were conducted. Copper addition to the base alloy facilitates the precipitation of chromium nitride and stabilizes it at elevated temperatures due to the increase of activity of Cr. With aging the alloy at 1293 K, copper added alloy reduces the resistance to pitting corrosion due to the precipitation of deleterious chromium nitrides compared with that of the base alloy. Experimental results are in good agreement with thermodynamic calculations of elemental activity and the driving force for the precipitation of chromium nitrides.