Thermal stability, Mechanical and Electrical Properties of Nano crystalline Cu99.5 Zr0.5 Alloy

Research Work

Cryogenic high energy ball milling was used to
synthesize nanocrystalline Cu and Cu-0.5at%Zr
alloys by mechanical alloying and consolidation by
hot pressing at 550ºC temperature. The grain size
stability of nanocrystalline Cu is improved by the Zr
addition. Microstructural characterization using X-ray
diffraction and transmission electron microscopy
provided evidence for the formation of a Cu- Zr
alloy solid solution with nanocrystalline size after
hot pressing. The alloy exhibited a higher hardness
(3.31 GPa), and shear strength (550 MPa) than nanocrystalline
pure Cu however, the electrical resistivity
is increased in the alloy.

Grain size stability and hardness in nanocrystalline
Cu-AI-Zr and Cu-AI-Y alloys [Work submitted for

Cryogenic high energy ball milling has been used to
synthesize nanocrystalline Cu-14AI, Cu-12AI-2Zr and
Cu-12AI-2Y alloys by mechanical alloying. The alloys
were studied with the aim of comparing the effect
of substituting Y and Zr in place of AI, in Cu-AI alloys,
on the grain size stability at elevated temperatures.
The as-milled alloys were subjected to annealing
at various temperatures between 200-900ºC and
the resulting grain morphology has been studied
using X-ray diffraction and transmission electron
microscopy. The addition of Y results in significantly
reduced susceptibil ity to grain growth whereas in
case of CuAI and CuAIZr alloys, the susceptibility
to grain growth was much higher. The hardness is
substantially increased due to Zr and Y addition in
the as-milled CuAI powders. However, the hardness
of Cu-12AI-2Zr gradually decreases and approaches
that of Cu-14AI alloy after the annealing treatment
whereas in case of Cu-12AI-2Y alloy, the relative
drop in the hardness is much lower after annealing.

Accordingly, the efficacy of grain size stabilization by Y
addition at high homologous temperatures has been
explained on the basis of a recent thermodynamic stabilization models.

This research is part of the Indo-US Research Fellowship Program:

The article text was originally released in their newsletter.

US Host: Dr. Carl C Koch
IUSSTF Research Fellow: Debdas Roy