Improving the stability of nanocrystalline metals

Background:

The stability of nanocrystalline metals is a fundamental issue for future potential applications. Adding solutes, impurity elements and second phase particles can stabilize a nanostructure against grain growth. The underlying mechanism for controlling the stability – reduction of grain boundary energy by solute segregation or kinetic barriers for grain boundary migration by solute drag or second phase particles- is still under discussion and is investigated in detail in the Co-Cu model system in this project. Synthesis of bulk nanocrystalline metallic materials with different types and amounts of solutes and impurity elements, is conducted by severe plastic deformation and electrodeposition. The Co-Cu system has a positive heat of mixing, and the formation of non-equilibrium solid solutions can be studied. Furthermore, it exhibits extraordinary magnetic properties like giant magnetoresistance.

The initial microstructures (e.g. texture, etc.) of the synthesized nanostructures are strongly dependent on the used processing method used. In this project, a direct comparison of the thermal stability of electrodeposited and severe plastically deformed nanomaterials and the influence of their initial microstructure regarding different defect density, different types of grain boundaries and distribution of solutes on stability, can be conducted. This helps to understand the relation of structure to stability and identify the mechanism controlling stability. Special attention is drawn to the influence of solutes and impurity elements on the mechanical properties of the nanocrystalline materials. Possible formation of supersaturated solid solutions, decomposition processes, their influence on thermal stability and the mechanism behind bulk mechanical alloying are investigated as well.

The results of the project can be used as a basis for enhancing structural stability in nanocrystalline materials and creating stable bulk nanocrystalline metallic materials in the future, which increase their potential applications.

 

                                

 

Acknowledgements: Funding for this research is provided by the Austrian Science Fund (FWF) under the project: J 3468-N20.

Duration: 01.09.2013-31.08.2016

Full –texts of all publications can be found on the following website: www.researchgate.net/profile/Andrea_Bachmaier/publications

Scientific publications:

1. Bachmaier A., Rathmayr G.B., Apel D, Bartosik M., Zhang Z., Pippan R.: New insights on the formation of supersaturated solid solutions in the Cu–Cr system deformed by high-pressure torsion, Acta Materialia 69, 2014, 301 – 313.
http://dx.doi.org/10.1016/j.actamat.2014.02.003

2. Bachmaier A., Neubauer E., Kitzmantel M., Pippan R., Motz C.: Microstructural evolution in immiscible alloys processed by High-Pressure Torsion, IOP Conference Series: Materials Science and Engineering 63, 2014, Article number 012023.
http://dx.doi.org/10.1088/1757-899X/63/1/012023

3. Bachmaier, A., Motz C, Pippan, R.: Herstellung höchstfester und thermisch stabiler nanokristalliner metallischer Verbundwerkstoffe mit Hochverformung (Manufacture of ultra high-strength and thermally stable nano-crystalline metallic composite materials with high deformation), Metall 68, 2014, 477-479.
http://dx.doi.org/10.13140/RG.2.2.28263.24487

4. Bachmaier A., Motz C.: On the remarkable thermal stability of nanocrystalline cobalt via alloying, Materials Science and Engineering A 624, 2015, 41–51.
http://dx.doi.org/10.1016/j.msea.2014.11.062

5. Bachmaier A., Aboulfadl H., Pfaff M., Mücklich F., Motz C.: Structural evolution and strain induced mixing in Cu-Co composites studied by transmission electron microscopy and atom probe tomography, Materials Characterization 100, 2015, 178-191.
http://dx.doi.org/10.1016/j.matchar.2014.12.022

7. Bachmaier A., Stolpe M., Müller T., Motz, C.: Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment, IOP Conference Series: Materials Science and Engineering 89, 2015, 012017.
http://dx.doi.org/10.1088/1757-899X/89/1/012017

8. Bachmaier A., Paff M., Stolpe M., Aboulfadl H., Motz, C.: Phase separation of a supersaturated nanocrystalline Cu-Co alloy and its influence on thermal stability, Acta Materialia 96, 2015, 269-283. http://dx.doi.org/10.1016/j.actamat.2015.05.053

9. Bachmaier A., Schmauch J., Aboulfadl H., Verch A., Motz, C.: On the process of co-deformation and phase dissolution in a hard-soft immiscible Cu-Co alloy system during high-pressure torsion deformation, Acta Materialia 115, 2016, 333-346.
http://dx.doi.org/10.1016/j.actamat.2016.06.010

10. Müller T., Bachmaier A., Neubauer E., Kitzmantel M., Pippan R.: Strong and stable nanocomposites prepared by high-pressure torsion of Cu-coated Fe powders, Metals 6(10), 2016, 228.
http://dx.doi.org/10.3390/met6100228

Other publications

1. Bachmaier A., Motz C.: New challenges to characterize bulk nanocomposites, in: Prakt. Met. Sonderband 46 (2014), 289-294. doi: http://dx.doi.org/10.13140/RG.2.2.18196.91524

2.Bachmaier, A., Motz C.: Hochfeste nanokristalline Metallverbunde – ein Werkstoff mit Zukunft, in: Magazin Forschung 02/2014, 8-11, Universität des Saarlandes, Saarbrücken, Germany.
doi: http://dx.doi.org/10.13140/RG.2.2.29521.53603

Invited presentations

1. Bachmaier A., Rathmayr G.B., Apel D, Bartosik M., Zhang Z., Motz C., Pippan R.: The generation of supersaturated solid solutions in the Cu-Cr system, Plasticity 2014, Freeport, Bahamas, 03.‑08.01.2014

2. Bachmaier A., Hohenwarter A., Pippan R.: The generation of nanocomposites and supersaturated solid solutions by SPD, TMS 2014, San Diego, USA, 16.-20.02.2014

3. Bachmaier A.: Mikrostruktur und Eigenschaften hochverformter metallischer Verbundwerkstoffe, +composites SAAR, Saarbrücken, Germany, 06.05.2014

4. Bachmaier A., Pippan R.: The formation of supersaturated solid solutions in immiscible alloys processed by severe plastic deformation, seminar lecture, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany, 15.05.2014

5. Bachmaier A.: Mikrostruktur und Eigenschaften hochverformter Metalle und Verbundwerkstoffe, Kupfersymposium, Frankfurt, Germany, 5.-6.11.2014

6. Bachmaier A., Motz C., Pippan R.: Phase decomposition of metastable nanocrystalline solid solutions and its influence on thermal stability, XXIV International Materials Research Congress 2015, Cancun, Mexiko, 16.-20.08.2015

7.Bachmaier A., Motz C., Pippan R.: Generation of exceptionally stable nano-structures through bulk mechanical alloying of immiscible alloy systems by SPD, Plasticity 2016, Kona, USA, 03.-09.01.2016

8. Müller T., Bachmaier A., Schöberl T., Pippan R.: Nanolamellar structures combining amorphous and crystalline phases- a way to improve strength and ductility, EMN Meeting on Metallic Glasses, Kuala Lumpur, Malaysia, 12.-16.09.2016

Talks at international conferences

1. Bachmaier A., Motz C., Pippan R.: Deformationsinduzierte Phasenauflösung und erhöhte thermische Stabilität in hochverformten metallischen Legierungssystemen, 60. Metallkunde Kolloquium, Arlberg, Austria, 22.-24.04.2014

2.Bachmaier A., Aboulfadl H., Pauly C., Neubauer E., Kitzmantel M., Pippan R., Motz C.: Microstructure and thermal stability of Cu–Co nanocomposites processed by HPT powder consolidation, NanoSPD 6, Metz, France, 30.06.- 04.07.2014

3. Bachmaier A., Aboulfadl H., Pfaff M., Motz C.: New challenges to characterize bulk nanocomposites, Metallographie Tagung, Leoben, Austria, 17.-19.09.2014

4. Highlight-Talk: Bachmaier A., Motz C., Kormout K., Pippan R.: Different Approaches to Enhance Thermal Stability of Nanocrystalline Materials, MSE Darmstadt, Germany, 23.-25.09.2014

5. Bachmaier A., Aboulfadl H., Pfaff M., Mücklich F., Motz C.: On the mechanism of strain induced mechanical mixing in Cu-Co composites studied by transmission electron microscopy and atom probe tomography,  ICSMA-17, Brünn, Czech Republic, 9.-14.08.2015

6. Bachmaier A., Pfaff M., Stolpe M., Aboulfadl H., Motz C.: Thermal stability and phase decomposition of a supersaturated nanocrystalline Cu-Co alloy. 22nd International on Metastable and Nano Materials (ISMANAM), Paris, France, 13.-17.07.2015

7. Bachmaier A., Pfaff M., Schmauch J., Aboulfadl H., Stolpe M., Müller T., Motz C.: Phase separation of metastable nanocrystalline Cu-Co solid solutions during thermal treatment and its influence on thermal stability, 1. HPT-SPD Seminar, Erich Schmid Institut, Leoben, Austria, 22.-24.07.2015

8. Bachmaier A., Stolpe M., Müller T., Motz C.: Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment, 36th Risoe International Symposium, Risö, Denmark, 07.-11.09.2015

9. Müller T., Bachmaier A., Pippan R.:  Electrodeposition of nano-scaled multilayer structures in the Fe-P system, International Workshop on Electrodeposited Nanostructures, Balatonfüred, Hungary, 10.-12.09.2015

10. Müller T., Bachmaier A., Pfeifenberger M., Schöberl T., Pippan R.: Mechanical properties of amorphous/crystalline multilayer structures in the Fe-P system, DPG Spring Meeting, Regensburg, Germany, 6.-11.03.2016

11. Bachmaier A., Schmauch J. Aboulfadl H., Zamanzade M., Verch A., Motz C.:  Extraordinary structural stability and hardness by decomposition of metastable nanocrystalline solid solution, Thermec 2016, Graz, Austria, 30.05-03.06.2016

12. Bachmaier A., Schmauch J. Aboulfadl H., Pippan R., Motz C.: Tailored nanostructures with enhanced structural stability and strength by decomposition of metastable nanocrystalline solid solutions, 62. Metallkunde‐Kolloquium, Lech am Arlberg, Austria, 11. – 13.04.2016

13. Müller T., Bachmaier A., Schöberl T., Pippan R.: Deformation behavior and size effects in electrodeposited amorphous/crystalline multilayer structures in the Fe-P system, 23rd International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM), Japan, 03.‑08.07.2016

14. Bachmaier A., Schmauch J., Aboulfadl H., Verch A., Krenn H., Pippan R.: Tailoring the mechanical and magnetic properties of nanocrystalline materials by decomposition of metastable solid solutions, GSAM2016, Fukuoka, Japan, 28.-31.07.2016

15. Müller T., Bachmaier A., Schöberl T., Pippan R.: Size effects and micromechanical testing of Fe-P amorphous/crystalline multilayer structures, MSE2016, Darmstadt, Germany, 27.-29.09.2016

Poster at international conferences

1. Bachmaier A., Rathmayr G.B., Apel D, Zhang Z., Pippan R, Motz C.: Formation of supersaturated solid solutions and mechanical properties in immiscible Cu-Cr deformed by High-Pressure Torsion, Schöntal Symposium, Germany, 24.-28.02.2014

2. Bachmaier A., Pippan R., Motz C.: Improving thermal and mechanical stability of nanostructured materials, Gordon Research Conference, Boston, USA, 13.-18.07.2014

3. Bachmaier A., Pfaff M., Motz C.: Strain induced mechanical mixing in Cu-Co composites studied by transmission electron microscopy, Conference on In-Situ and Correlative Electron Microscopy, Saarbrücken, Germany, 15.-16.10.2014

4. Müller T., Bachmaier A., Motz C.: Microstructure and properties of electrodeposited Cu-Co alloys, MSE 2014, Darmstadt, Germany, 22.-26.09.2014

5. Bachmaier A., Aboulfadl H., Pfaff M., Motz C.: Atomic scale characterization of deformation induced mixing in immiscible Cu-Co composite materials, Euromat 2015, Warsaw, Poland, 20.‑24.09.2015

6. Bachmaier A., Aboulfadl H., Schmauch J., Pippan R., Motz C.: Investigating the deformation induced formation of supersaturated solid solutions using atom probe tomography and transmission electron microscopy, European APT Workshop, Leoben, Austria 6.-9.10.2015

7. Müller T., Bachmaier A., Motz C.: Gepulste Elektrodeposition von nanokristallinem Co und Co/Cu Legierungen, VDI Forum Saar, Sulzbach (Saar), Germany, 15.04.2016

8. Müller T., Bachmaier A., Schöberl T., Pippan R.: Synthesis and mechanical characterization of electrodeposited multilayer structures in the Fe-P system, The Materials Chain International Conference - From Discovery to Production, Bochum, Germany, 30. 05.-01.06.2016 

9. Müller T., Bachmaier A., Pippan R.: Structure evolution of copper coated iron powder during deformation by high pressure torsion, MSE2016, Darmstadt, Germany, 27.-29.09.2016     

Prices and Awards

Müller T.: Förderpreis des VDI Bezirksverein Saar für eine herausragende Masterarbeit in der Fachrichtung Werkstoffwissenschaften, 15.04.2016, Sulzbach (Saar), Germany