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Materials Frontier No.186

Title:Ultrafine Grained Precipitation Hardened Aluminum Alloys and Influence of Addition of Ceramic Reinforcement
Speaker:Dr. Kaka Ma  Department of Mechanical Engineering Colorado State University
Date/Time:2017-6-5, 4:00~5:00pm
Veune:Yiuching Lecture Hall, Xu Zuyao Building
Inviter:Liang Jiamiao
Dr. Ma received her B.S. in materials physics from University of Science and Technology of China in 2006 and earned her Ph.D. in materials science and engineering from University of California (UC), Davis in Dec. 2010. Before joining Colorado State University as an assistant professor, she performed postdoctoral research at UC Davis and UC Irvine. She was also an instructor for an upper-division undergraduate course, titled “Materials Selection in Engineering Design”, when she was at UC Davis. Dr. Ma’s research interests sit at the interface of materials science, mechanical engineering, and sustainability. She is interested in innovation of advanced nanomaterials with high performance, improved reliability, and extended lifetime for next-generation structural, electronic, and energy components. Her previous research focused on fabrication and characterization of nanostructured or ultrafine grained materials ranging from thermal barrier coatings, aluminum alloys to metal matrix composites. Her recent research activities focus on multiple-scale precipitation strengthened Al alloys and composites, metal additive manufacturing (AM) and sustainability issues associated with AM. She has published 28 peer-reviewed and referred journal papers. She has given more than thirty presentations (six invited) at international technical conferences such as TMS (The Minerals, Metals & Materials Society) and MS&T. Dr. Ma serves on the reviewer board for several international circulated journals, including Materials Science & Engineering A, Metallurgical and Materials Transactions A, Nature Communications, Scientific Reports, Surface and Coatings Technology, Journal of Alloys and Compounds, Material Research Letters etc.

The strategy of creating nanostructures has been applied in a variety of metals and alloys to achieve unprecedented mechanical properties. Primary approaches include: (1) reducing the grain size to the nanoscale for Hall-Petch strengthening, and (2) using phase transformation to introduce nanoscale precipitates for dislocation shearing or Orowan strengthening. When precipitation occurs in alloys with nanoscale or ultrafine matrix grains (i.e., with a high volume of grain boundaries), the complexity in microstructural evolution leads to significant challenges in predicting and understanding the corresponding mechanical behavior. Using Al-Mg-Zn-(Cu) alloys as a model system, this talk will provide an overview of recent work on ultrafine grained Al 7000 series alloys and their enhanced mechanical performance. Coupling of intragranular dislocations and precipitates in ultrafine grains as well as lamellar grain structure with low angle grain boundaries led to simultaneous improvement in strength and ductility. In addition, increasing attentions have been paid to the composites consisting of Al-Mg-Zn-(Cu) alloy matrix and ceramic reinforcement due to the potential of further improving strength and wear resistance. Microstructure and mechanical performance of ultrafine grained Al composites reinforced with B4C particles will be discussed in this presentation as well.

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