Abstracts - Conference Planning and Management - Iowa State ...

Quantitative Tensile Testing at the Nanoscale
Matthew Kramer
Materials Sciences and Engineering, Ames Laboratory
USDOE, 225 Wilhelm Hall, Ames Laboratory, Ames, 50011, US
Phone: 515 294 0276, Email: mjkramer@ameslab.gov
Ying Zhang
Materials Sciences and Engineering, Ames Laboratory, Ames, Iowa
Joong Mok Park
Materials Sciences and Engineering, Ames Laboratory, Ames I, Iowa
Zhiwei Shan
Hysitron, Inc, Minneapolis, MN
Julia Deneen Nowak
Hysitron, Inc, Minneapolis, MN
Oden L. Warren
Hysitron, Inc, Minneapolis, MN
Abstract:
Conventional transmission electron microscopy (TEM) tensile holders provide only constant
displacement rate. Sample geometry is such that only a small portion of the sample is thin enough for
electron imaging. In situ deformation studies, using this type of holder, is qualitative at best. To obtain
quantitative nanomechanical properties, the sample geometry, load-frame and associated control
electronics must be designed specifically for this purpose. Using the advanced control electronics and
nano-indenter transducer, Hysitron has modified their pico-indenter to perform load/displacement
control of electron transparent samples in tension. These innovations also include a unique design to
eliminate initial load transients, active damping of the load or displacement control and a removable
sample holder for ease of sample preparation. Ames Laboratory has developed techniques to fabricate
nanowires (~ 150 x 50 nm up to 10’s of µm in length) from a wide variety of transition metals and &lt
70 nm thick single crystal films of Cu. We are now capable of testing polygrained wires of Al, Ti, Cu
and Au under both constant load and constant strain rate. Using a focused ion beam we will be able to
extract thin single grain foils with orientations which will be both favorable and unfavorable to slip in
fcc Cu. Together with high speed imaging in the TEM, we will be able to study the dynamics of the
deformation mechanism in both nanoscale polygrained materials and slip systems in single crystals.
Key science questions for nanograined materials are 1) what is the role of grain size in grain boundary
sliding and 2) how is this affected by loading rate? Doing these studies in the TEM, we can also track
the orientations of the various grains to see if certain grain boundaries are stiffer than others. Key
science questions for single grain samples are 1) what are the relative length scales necessary for
dislocations motion, 2) what is the effect of grain size in strengthening alloys and 3) do the defect
mechanisms change as the cross section is reduced to < 20 nm? Results of our preliminary studies will
be presented.
Society of Engineering Science ▪ 47 th Annual Technical Meeting 310