Phase separation in NiTiNi2TiAl alloy system

This paper reports preliminary atom probe analysis of the phase decomposition occuring during solution treatment and subsequent ageing of a pseudo-binary NiTi(β)-Ni2TiAl(β′) alloy. Material was treated for 1 h at each of 400, 600 and 800°C. Material aged at 400 and 600°C showed no signs of decomposition, however the material aged at 800°C showed clear signs of fine scale precipitation both in the field ion microscope image and by chemical atom probe analysis. The precipitates were approximately 10 nm in diameter and had a composition of Ni50Ti30Al20 (at.%) embedded in a matrix of composition approximately Ni50Ti44Al6 (at.%). These values are an indication of the position of the phase boundaries at 800°C. The suitability of this alloy system for further development and further atom probe characterization is discussed.