Papers by Author: Paweł Pączkowski

Abstract: The Ni64Cu9Fe8P19 alloy was prepared using 99.95 wt % Ni, 99.95 wt % Cu, 99.95 wt % Fe and Ni-P master alloy. The melt spun ribbon in as-cast state was characterized using of transmission electron microscope (TEM) and X-ray diffraction (XRD). The amorphous alloy was subjected to DTA and resistivity measurement in order to determine the thermal stability at elevated temperatures. The melt spun ribbon had a negative TCR=-2.23·10-6K-1 that is stable up to the Tg-dep=511K. At higher temperature Tg-int=560K the relative resistance starts to decrease and between 573K and 591K the rate of the decrease reaches TRC=-480.096 K-1. After the heating cycle to 633K, during cooling the alloy has a positive TRC=6.03·105 K-1. DTA curve presents the three exothermal stages with the onsets and peak values at I: Tx1=564K and T1=611K, II: Tx2=655K and T2=662K, III: Tx3=697K and T3=715K, respectively. The melting stage can be characterized by endothermic peak with Tm=1149K and Tl=1174K. On the base of the measurements the amorphous alloy was heated to the temperatures where subsequent transformations occurred. TEM study delivered information about formation of the M3P type tetragonal phosphide (a=9.040Å, c=4.462Å) nanocrystals within the amorphous matrix after the first stage of crystallization.

Abstract: In order to increase corrosion resistance, the NiTi shape memory alloy was covered by protection layers using glow discharge method. Samples were nitrided with some oxygen addition at temperatures: 350, 380, 400 and 800°C. Microstructure and sequence of obtained layers were studied applying X-ray diffraction technique as well as electron microscopy. Low temperature process produces a layers which consist of Ti3O5, TiN and Ni2Ti4O. Intermediate Ni3Ti layer was between Ni2Ti4O and NiTi matrix. High temperature process forms TiO2 and TiN with interlayer Ti2Ni. Surface does not contain phase with Ni, which is considered as toxic element.