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Strengthening Mechanisms in Nanostructured Materials

thesis
posted on 29.07.2022, 20:34 authored by Yailuth Alexandra Loaiza LoperaYailuth Alexandra Loaiza Lopera

Understanding the behavior of materials with nanoscale features is important because of both the  size  of  engineering  devices  and  the  internal  microstructure  of  more  bulk  materials.  Many electronic  components  have  been  miniaturized  in  recent  years  to  attend  the  high  demand  of technology development. Similarly, new stronger bulk metallic materials use nm-scale grain sizes or  precipitates  to  increase  their  strength  over  more  conventionally  processed  alloys.  Nanoscale testing   also   offers   a   route   for   mechanical   behavior   understanding   at   the   microscale. Nanoindentation  has  been  used  to  find  structure-properties  relationships  of  nanostructured materials due to its high load-depth resolution and versatility of the test. Nanoindentation can be used  to  find  hardness  and  modulus  of  the  materials,  important  characteristics  to  evaluate mechanical  performance.  An  introduction  to  strengthening  mechanism  and  generalities  of nanoindentation is shown in Chapter 1.

This thesis explores how traditional strengthening mechanisms for bulk materials, can be  applied  to  nanomaterials  and  how  the  microstructure  could  be  tailored  to  achieve  the  desired outcomes on the specific materials studied. The first one is the study of mechanical properties of Nanometallic  Foams  (NMF)  and  its  relationship  with  the  nanostructure.  NMFs  of  pure  copper, CuNi and CuZn alloys were fabricated and tested to find the predominant structural and chemical parameters  of  the  mechanical  properties.  Research  on  how  to  control  and  tailor  the  structural parameters of NMF with viscosity of the precursors is shown in Chapter 2. The relative density was  the  most  predominant  parameter  among  the  structural  parameters  studied.  However,  when relative density parameter is isolated, NMF  are more susceptible to strengthen by second phase precipitation instead of solid solution. The solid solution strengthening mechanism was validated with  MD  simulation  and  agrees  with  the  experimental  findings  that  showed  the  addition  of  Ni atoms to Cu have a moderate effect on the mechanical properties. Chapter 3 presents these findings The  second  example  presented  shows  the  strengthening  effect  of  precipitates  in  nanometallic multilayer. The precipitation was achieved by aging treatment. High temperature nanomechanical testing is also presented in Chapter 4. The third and final example, presented in chapter 5, shows how  the  second  phase  precipitation  and  dispersion  strengthening  of  lead-free  solder  SAC  305 compares  between  samples  aged  for  nine  years  at  body  temperature  and  an  accelerated  aging treatments.

History

Degree Type

Doctor of Philosophy

Department

Materials Engineering

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

David F Bahr

Additional Committee Member 2

Kevin P. Trumble

Additional Committee Member 3

Xinghang Zhang

Additional Committee Member 4

Kejie Zhao