Effect of particle size on the chemical composition of Ti–Ni-base spark erosion powder obtained in liquid argon

Chem. Met. Alloys 4 (2011) 188-199

https://doi.org/10.30970/cma4.0179

Gennady MONASTYRSKY, Patrick OCHIN, Guillaume Y. WANG, Victor KOLOMYTSEV, Yuri KOVAL, Andriy GILCHUK,Vitaliy TINKOV, Anatoliy SHCHERBA, Sergey ZAHARCHENKO

Ti–Ni–Zr and Ti–Ni–Hf powders were obtained by the spark-erosion method in liquid argon from preliminary melted shape memory master alloys. The morphology of the particles with typical sizes between 5 and 50 μm, their surface as well as the cross-section structure are very similar to typical ones of gas atomized powders. The internal structure of such particles of both compositions is transient between cellular and equiaxed-type. Nanosized particles of spherical shape usually gather in agglomerates. The chemical compositions of micron-sized particles were investigated very carefully. It was statistically well proven that while the compositions of particles with sizes more than 10 μm are close to the composition of the master alloy, the compositions of the smallest particles are drastically different. The results obtained allow claiming that such important changes in the chemical compositions of powders are connected with the different rate of evaporation of elements due to their different vapor pressures. The size dependence of the composition is related to the different cooling rate of particles of different sizes.

Particle size distributions F(R) for Ti–Ni–Hf and Ti–Ni–Zr–Cu spark erosion powders.

Keywords

Powders / Gas atomized powders / Spark-erosion method / Shape memory alloys / Spark plasma sintering / Ti–Ni–Hf / Ti–Ni–Zr