Carnegie Mellon Department of Materials Science and Engineering Carnegie Mellon University 4315 Wean Hall Pittsburgh, Pennsylvania 15213-3890 Email rollett@andrew.cmu.edu Phone 412-268-3177 Fax 412-268-7596 Anthony D. Rollett

June 24, 2015 To Whom It May Concern, I am delighted to write on behalf of Suraj Rao and to very strongly recommend him as a thoroughly professional and bright young engineer. Suraj joined my group last September (2014) shortly after he started his Masters program in the Materials Science & Engineering department at CMU. I have become heavily involved in additive manufacturing and one of the projects was a one-year effort in collaboration with Alcoa on 3D printing of aluminum powders. I asked Suraj if he would like to participate and he readily agreed. I directed him to learn about the powder characterization techniques that other students in my group had developed and apply them to the powders that Alcoa gave us to work with. He quickly learned about transmission optical microscopy, scanning electron microscopy, and image analysis (e.g. with ImageJ) and was producing useful results within a few weeks. Part way through the project we identified a serious discrepancy between our results and those from Alcoa. Suraj worked with me to analyze this discrepancy, identify a difference between number-based averaging and volume-based averaging, re-process the data and report on the much improved comparison. Subsequently we acquired several datasets of computed tomography at the Advanced Photon Source (Argonne Natl. Lab.) on samples of AM materials provided by Alcoa. The raw data then had to be reconstructed into 3D images and the results analyzed for porosity content. Suraj took charge of analyzing the 3D reconstructed images (mainly with Avizo), which are so large that we had to purchase a state of the art workstation with 225 gigabytes of RAM. Those images revealed large variations in porosity as a function of processing conditions. He is in the process of writing a paper on this work, which I expect will attract substantial attention in the AM community because nobody has obtained synchrotron data and analyzed it to the level of detail that we have here at CMU. In terms of written communications, Suraj writes very well. In terms of oral communication, I early on had him give presentations on his work to the joint CMU-Alcoa team, which he did extremely well. He comes across as pleasant, knowledgeable and professional. Altogether

he performed well above expectations and was a key member of the project team. I fully expect him to be highly successful in whatever situation he finds himself. Sincerely,

Professor, Materials Science & Engineering Brief bio: I have been a Professor of Materials Science and Engineering at Carnegie Mellon University (CMU) since 1995. Previously, I worked for the University of California at the Los Alamos National Laboratory. At LANL, I spent ten years in management with five years as a Group Leader (and then Deputy Division Director) at Los Alamos, followed by five years as Department Head at CMU (1995-2000). I have been a Fellow of ASM since 1996, Fellow of the Institute of Physics (UK) since 2004, and a Fellow of TMS since 2011. I received the Cyril Stanley Smith Award for contributions to microstructural science from TMS in 2014. My research group has about ten students and is supported by several agencies including NIST, America Makes, DARPA, AFOSR, ONR, NSF, as well as companies such as Alcoa, Boeing and Medtronic. The main focus of my current research is on the measurement and prediction of microstructural evolution, along with the relationship between microstructure and properties, with a particular emphasis on three-dimensional effects.