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