A CO 2 laser has been employed to join binary Ti 50 Ni 50 and Ti 49.5 Ni 50.5 shape-memory alloys (SMAs), with an emphasis on the shape-memory and corrosion characteristics. Experimental results showed that a slightly lowered martensite start (M S ) temperature and no deterioration in shape-memory character of both alloys were found after laser welding. The welded Ti 50 Ni 50 , with an increased amount of B2 phase in the weld metal (WM), had higher strength and considerably lower elongation than the base metal (BM). Potentiodynamic tests revealed the satisfactory performance of laser-welded Ti 50 Ni 50 in 1.5 M H 2 SO 4 and 1.5 M HNO 3 solutions. However, the WM exhibited a significantly higher corrosion rate and a less stable passivity than the BM in artificial saliva. On the other hand, the pseudoelastic behavior of the laser weld was investigated only for the Ti 49.5 Ni 50.5 alloy, to facilitate tension cycling at room temperature. The cyclic deformation of Ti 49.5 Ni 50.5 indicated that the stress required to form stress-induced martensite ( m ) and the permanent residual strain ( p ) were higher after welding at a given number of cycles (N ), which were certainly related to the more inhomogeneous nature of the WM.
An atmospheric pressure nitrogen plasma jet sustained by a repetitive pulsed DC power source is studied. The afterglow characteristics of this plasma jet are studied by an optical emission spectrometer and thermocouples. The effects of the process parameters, namely the applied voltage and the gas flow rate, on the plasma characteristics are investigated. It is shown that the plasma reactivity is controlled by the power deposition to the plasma as well as the decay process of the reactive species upon formation. The reactivity increases with the increase in the applied voltage and with the decrease in the gas flow rate. The jet temperature is primarily controlled by the power density, and it increases with the increase in the applied voltage and with the decrease in the gas flow rate. These observations suggest that the plasma reactivity and the jet temperature of this plasma jet can be nearly independently controlled.
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