Research

Current Projects

1. Collaboration with Prof. Robert Suter's group in Physics to measure 3D grain maps and perform tomography on voids in ductile fracture, using high energy x-rays at the APS.
2. Collaboration with Prof. Robert Suter's group in Physics to measure microstructure and strain fields around fatigue cracks, using high energy x-rays at the APS; AFOSR support.
3. Working with Boeing to investigate the effect of different melting technologies on Ti-6Al-4V microstructure and properties.
4. Working with Medtronic to investigate the effect of microstructure (incl. texture) on properties of Nitinol.
5. Investigation of the properties of powders used in 3D printing of metals using metallography and computed tomography; America Makes support.
6. Development of beta-stabilized Ti alloys in additive manufacturing; NSF support for DMREF collaboration with Iowa State and Georgia Tech.
7. Application of 3D printing of superalloy heat exchangers for supercritical CO2.
8. Investigation of micromechanics of void formation under spall conditions.
9. Interface character and orientation relationships in advanced steels.
10. Highly scalable code for elasto-viscoplastic micromechanics.
11. Constitutive (stress-strain) relations for Ti-6242 for high temperature service.
12. Machine vision applied to classification of powders used for 3D printing of metals (collab. with E.A. Holm).

Research Direction

The relationship between materials structure, or microstructure, and the properties of materials continues to stimulate the curiosity of materials scientists. Our research focuses on the relationship of mechanical properties to microstructure (including texture) and the development of tools for quantitative understanding.

There are many unresolved issues in microstructural evolution, such as how to make quantitative predictions of texture development during plastic deformation and subsequent annealing. The "abnormal" growth of certain types of grains at the expense of others clearly depends on the properties of the grain boundaries and on the driving forces for growth. Measurement of the grain boundary properties over the entire range of crystallographic types provides one key input to the problem. Understanding the effect of (anisotropic) grain boundary properties on microstructural evolution (grain growth, recrystallization) with Monte Carlo and cellular automata provides another essential part of the puzzle. Simulation and characterization of plastically deformed microstructures provides yet another part of the picture.

Since texture, i.e. crystallographic preferred orientation, plays a dominant role in determining the anisotropy of a material,it is also important to verify the relationships. The spatial arrangement of orientations has recently been shown to interact strongly with the development of non-uniform plastic flow or localizations. Also, there many opportunities for optimization of texture for mechanical and magnetic properties, e.g. in laminations for electrical motors. The combination of advanced characterization tools and simulation techniques therefore provides an exciting approach to engineering the anisotropy of materials for optimum properties and performance.

In recent years, 3D printing of metals has become a very important technology for rapid prototyping, rapid deployment of new designs, advanced part design and new alloys [see: engineering.cmu.edu/research/next_manufacturing/].  The dominant powder bed technology means that metal powders are once again the focus of much attention.  CMU is bringing to bear its expertise in many different areas but in the Rollett group, advanced characterization with synchrotron radiation is a particular area of emphasis, along with collaboration with the Holm group to apply machine vision to classifying powders, for example.

Researchers and Collaborators

Current Researchers, Collaborators in the group:

Paul Chao

Shuchen Cong

Ross Cunningham

Allen Feng

Brian Gockel

Harshvardhan Jain

Shivram Kashyap

Jacky Lao

Keunho Lee

Evan Lieberman

Sudipto Mandal

Tugce Ozturk

Chasen Ranger

Samikshya Subedi

Vahid Tari

Jake Vries

Sen Wang