Current affiliations curators’ Professor, Metallurgical Engineering Site Director, nsf industry/University Cooperative Research Center for Friction Stir Processing




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НазваниеCurrent affiliations curators’ Professor, Metallurgical Engineering Site Director, nsf industry/University Cooperative Research Center for Friction Stir Processing
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R. S. Mishra and A. K. Mukherjee, "Creep behavior of rapidly solidified and processed aluminum alloys," in Light Weight Alloys for Aerospace Applications, edited by E.W. Lee, K. V. Jata, N. H. Kim and W. E. Frazier, The Minerals, Metals and Materials Society, 1995, p319.

  • R. S. Mishra, W. B. Lee, A. K. Mukherjee and Y-W. Kim, "Mechanism of superplasticity in gamma TiAl alloys," in International Symposia on Gamma Titanium Aluminides, edited by Y-W. Kim, R. Wagner and M. Yamaguchi, (TMS 1995), p571.

  • R. S. Mishra and A. K. Mukherjee, "Effects of additives on plasma activated sintering of nanocrystalline alumina," Advances in powder metal and particulate materials - 1995, edited by M. Phillips and J. Porter, MPIF and APMI, 1995, p7-161.

  • R. S. Mishra and A. K. Mukherjee, "The origin of high strain rate superplasticity in powder metallurgy aluminum alloys," Advances in powder metal and particulate materials - 1995, edited by M. Phillips and J. Porter, MPIF and APMI, 1995, p10-155.

    1994

    1. T. R. Bieler, R. S. Mishra and A. K. Mukherjee, "The role of threshold stresses and incipient melting in high strain rate superplasticity," Materials Science Forum, 170-172 (1994) 65.

    1993

    1. R. S. Mishra and A. K. Mukherjee, "Recent advances on superplastic metals and metal based composites," 3rd Japan International SAMPE Symposium, (1993) 864.

    2. R. Sundaresan, R. S. Mishra, T. Raghu, A. G. Paradkar and M. C. Pandey, "Steady state creep behaviour of a mechanically alloyed Al-9wt% Ti alloy," 2nd International Conference on Structural Applications of Mechanical Alloying, (1993) 221.

    3. D. Banerjee, A. K. Gogia, T. K. Nandy, K. Muraleedharan and R. S. Mishra, Structural Intermetallics, Edited by R. Darolia, J. J. Lewandowski, C. T. Liu, P. L. Martin, D. B. Miracle and M. V. Nathal, The Minerals, Metals and Materials Society, 1993, p. 19.

    Research Highlights


    Creep and Superplasticity

    I have evaluated creep and superplastic behavior of a number of materials, including aluminum alloys and composites, titanium alloys, titanium aluminides, nickel base superalloys, quasicrystals, and nanocrystalline alloys. Some of my contributions include, models for threshold for diffusional creep in pure metals and dislocation creep in dispersion strengthened materials. When I started following the controversies involving creep of aluminum matrix composites, I thought that microstructural parameters influence the dominant creep micro-mechanisms. This led to the development of dislocation creep mechanism map. I still believe that the constitutive relationships for dislocation creep need to include microstructural parameters and we are working on this. Based on similar thought processes, I put together a mechanism transition map for high strain rate superplasticity in particle containing aluminum alloys. Some of my papers have been received quite well by other researchers (I have included a list of well cited papers). Working on nanocrystalline materials, I highlighted the fact that nanocrystalline materials exhibit different high temperature deformation kinetics. Detailed analysis has shown that the change in deformation rate cannot be completely accounted by the grain size alone. From 1999, I also started organizing creep symposium under the TMS umbrella.

    Five Key Publications on Creep and Superplasticity:

    • R. S. Mishra, "Dislocation creep mechanism map for dispersion strengthened materials," Scripta Metallurgica et Materialia, 26 (1992) 309. –First paper to extend Ashby type deformation mechanism map to dispersion strengthened materials using a microstructure based transitions for dislocation creep.

    • A. B. Pandey, R. S. Mishra and Y. R. Mahajan, "Steady state creep behaviour of silicon carbide particulate reinforced aluminium alloys," Acta Metallurgica et Materialia, 40 (1992), 2045. –A very comprehensive experimental paper on effect of volume fraction and size of reinforcement phase on creep mechanism. It is one of the highly cited papers in this field.

    • R. S. Mishra, A. G. Paradkar and K. N. Rao, "Steady state creep behaviour of a rapidly solidified and further processed Al-5 wt% Ti alloy," Acta Metallurgica et Materialia, 41 (1993) 2243. –This paper introduces a quantitative modification of the constitutive relationship for dislocation creep of dispersion strengthened alloys.

    • R. S. Mishra, T. K. Nandy and G. W. Greenwood, "The threshold stress for dislocation-particle interaction controlled creep," Philosophical Magazine A, 69 (1994) 1097. –First paper to propose a physics-based model for attractive dislocation-particle interaction and resultant threshold stress.

    • R. S. Mishra, T. R. Bieler and A. K. Mukherjee, "Superplasticity in powder metallurgy aluminium alloys and composites," Acta Metallurgica et Materialia, 43 (1995) 877. –First critical review of high strain rate superplasticity in powder metallurgy aluminum alloys and composites. The paper has been cited very well by the researchers in this field.


    Processing and Properties of Bulk Ultrafine Grained Materials

    Ultrafine grained materials are defined as materials with grain size <1m. I am including my efforts on nanocrystalline materials under this category. My interest in bulk ultrafine grained materials was motivated by two questions: (a) what is the critical grain size below which the micro-mechanisms involved in mechanical behavior would change? (b) how to process bulk ultrafine grained materials at elevated processing temperatures without excessive grain growth? My initial work was on synthesis of ceramics with high-hardness and high toughness. The work resulted in a US patent on alumina-diamond nanocomposite and an invention disclosure on alumina-niobium nanocomposite apart from research publications. The main accomplishment was synthesis of fully dense nanocrystalline materials using high pressure and low temperatures. At UMR, I have focused on bulk nanostructured aluminum alloys using various powder metallurgy approaches. Most of the work has been done in collaboration with Boeing and Pratt & Whitney. We have managed to get funding from NSF, AFOSR and DARPA to pursue some of these research activities. We are currently working on obtaining a combination of high strength and good ductility. We have succeeded in obtaining strength of 700 MPa and ductility of >5% using secondary processing of rolling and forging in ultrafine grained aluminum alloy under the DARPA program with Boeing. By understanding the flow behavior at elevated temperatures, we have managed to find a narrow temperature range where secondary processing results in improved ductility without the loss of strength.

    Five Key Publications/Patent on Ultrafine Grained Materials:

    • R. S. Mishra, C. E. Lesher and A. K. Mukherjee, “High pressure sintering of nanocrystalline -Al2O3,” J. American Ceramic Society, 79 (1996) 2989. –This paper reported the synthesis of fully dense nanocrystalline alumina using high pressure sintering. The use of high pressure allowed lower sintering temperatures.

    • R. S. Mishra, R. Z. Valiev, S. X. McFadden and A. K. Mukherjee, “Tensile Superplasticity in Nanocrystalline Nickel Aluminide” Materials Science and Engineering A, A252 (1998) 174. –First paper to report superplasticity in nanocrystalline intermetallic alloy. Severe plastic torsional straining was used to produce bulk nanocrystalline specimens.

    • R. S. Mishra, C. E. Lesher and A. K. Mukherjee, U.S. patent (5,728,637) on “Nanocrystalline Alumina-Diamond Composites,” March 17, 1998.

    • S. X. McFadden, R. S. Mishra, R. Z. Valiev, A. P. Zhilyaev and A. K. Mukherjee, “Low temperature superplasticity in nanocrystalline nickel and metal alloys,” Nature, 398 (1999) 684. –First paper to report superplasticity at 0.4Tm. The paper highlighted that the grain refinement to anocrystalline range leads to extraordinary superplastic behavior.

    • R. S. Mishra, R. Z. Valiev, S. X. McFadden, R. K. Islamgaliev and A. K. Mukherjee, “High strain rate superplasticity from nanocrystalline Al alloy 1420 at low temperatures,” Philosophical Magazine A, 81 (2001) 37. –This paper highlights that the ultrafine grained materials show change in micromechanism of superplastic deformation. The kinetics of deformation was found to be lower even after the typical grain size and temperature normalization.


    Friction Stir Welding and Processing

    When I started research work on friction stir welding with the help from Murray Mahoney of Rockwell Scientific, I saw the opportunity to expand this technique beyond joining. So far we have obtained three US patents on selective superplasticity, microforming and channeling using friction stir processing. I collaborated with Kumar Jata and Murray Mahoney to start co-organizing symposium on friction stir welding and processing under the TMS umbrella. We recognized that publication of proceedings in this fast growing field will be very useful. I have written the first comprehensive review on friction stir welding and processing. It was published in the Materials Science and Engineering: Reports journal. I selected this review journal based on the impact factor (currently 11.8, highest among any materials science journals). Currently we are focusing on the fundamentals of microstructural evolution during friction stir processing and its influence on properties. Using small tool design, we have managed to produce ultrafine grained aluminum alloys with ~0.7 m grain size in one pass. This has resulted in superplasticity below 200oC in aluminum alloys, as compared to >400oC for conventionally processed aluminum alloys. We have joined a four-university consortium on NSF Industry/University Cooperative Research Center. I have been able to get General Motors, Boeing, Pacific Northwest National Laboratory, and Friction Stir Link to join the UMR site as industrial members. The center operates on NSF funding as well as industrial membership fees.

    Five Key Publications/Patents on Friction Stir Processing:

    • R. S. Mishra, M. W. Mahoney, S. X. McFadden, N. A. Mara, and A. K. Mukherjee, “High strain rate superplasticity in a friction stir processed 7075 al alloy,” Scripta Materialia, 42 (2000) 163. –First paper on friction stir processing. The paper reported an innovative extension of the friction stir welding concept as a generic microstructural modification tool.

    • R. S. Mishra, U.S. patent (6,655,575) on “Superplastic forming of micro components,” December 2, 2003. –This patent describes a method to use friction stir processing to fabricate microcomponents from wide range of commercial metals.

    • R. S. Mishra and M. W. Mahoney, U.S. patent (6,712,916) on “Metal superplasticity enhancement and forming process,” March 30, 2004. –This patent is based on the work described in the first paper on friction stir processing published in 2000. It describes how use of friction stir processing can overcome several conventional superplastic forming limitations like, slow forming rates and limited sheet thickness. It also opens up new possibilities, such as, selective superplastic forming.

    • R. S. Mishra, U.S. patent (6,923,362) on “Integral channels in metal components and fabrication thereof,” August 2, 2005. –This patent describes how a defect formation during friction stir welding can be controlled to create a new manufacturing process. The concept leads to creation of integral channels for heat exchangers.

    • R. S. Mishra and Z. Y. Ma, “Friction Stir Welding and Processing,” Materials Science and Engineering R, 50 (2005) 1-78. –This is the first comprehensive review of friction stir welding and processing. It was listed by the Science Direct as 11th hottest paper among the materials science publications in the Oct.-Dec. 05 time frame.

    Selected Publications of R. S. Mishra

    (Impact of Scientific Publications)


    It is generally very difficult to judge the quality of scientific research and publications of a researcher. However, the ‘Science Citation Index’ provides one such measure. Hirsch has produced an h-index to measure output of a researcher based on citations (Nature, Vol 436, page 18 August 2005; arXiv:physics/0508025 v3 17 Aug 2005). A key definition is, “A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have fewer than h citations each. My current ‘h-index’ is 35, i.e. I have 35 papers that have been cited more than 35 times according to the Science Citation Index (as on March 13, 2011). This can be considered as an indirect testimony to the impact of my research efforts. My ‘n’ is 23 based on first publication in 1987. This gives ‘m=(h/n)’ of 1.52.


    To help with the interpretation of the numbers above, I am reproducing a paragraph from Hirsh’s paper, “Based on typical h and m values found, I suggest that (with large error bars) for faculty at research universities h ~ 12 should be a typical value for advancement to tenure (associate professor), and h ~ 18 for advancement to full professor. Fellowship in the American Physical Society should occur typically for h ~ 15 to 20. Membership in the US National Academy of Sciences should typically be associated with h ~ 45 and higher except in exceptional circumstances. Note that these estimates correspond roughly to typical number of years of sustained research production assuming an m ~ 1 value, the time scales of course will be shorter for scientists with higher m values. Note that the time estimates are taken from the publication of the first paper which typically occurs some years before the Ph.D. is earned.”



    Total number of publications-210; Listed below- Top 25

    (Scopus/ISI databases have been used)

    Paper

    Scopus citation

    ISI citation

    1. R. S. Mishra and Z. Y. Ma, “Friction Stir Welding and Processing,” Materials Science and Engineering R, 50 (2005) 1-78.

    406

    407

    1. S. X. McFadden, R. S. Mishra, R. Z. Valiev, A. P. Zhilyaev and A. K. Mukherjee, “Low temperature superplasticity in nanocrystalline nickel and metal alloys,” Nature, 398 (1999) 684.

    355

    341

    1. J.-Q. Su, T.W. Nelson, R. Mishra, M. Mahoney, “Microstructural investigation of friction stir welded 7050-T651 aluminium” Acta Materialia, 51 (2003) 713-729.

    249

    226

    1. R. S. Mishra, T. R. Bieler and A. K. Mukherjee, "Superplasticity in powder metallurgy aluminium alloys and composites," Acta Metallurgica et Materialia, 43 (1995) 877.

    196

    206

    1. R. S. Mishra, M. W. Mahoney, S. X. McFadden, N. A. Mara, and A. K. Mukherjee, “High strain rate superplasticity in a friction stir processed 7075 al alloy,” Scripta Materialia, 42 (2000) 163.

    197

    39

    1. A. B. Pandey, R. S. Mishra and Y. R. Mahajan, "Steady state creep behaviour of silicon carbide particulate reinforced aluminium alloys," Acta Metallurgica et Materialia, 40 (1992), 2045.

    155

    189

    1. Z. Y. Ma, R. S. Mishra and M. W. Mahoney, “Superplastic deformation behavior of friction stir processed 7075Al alloy,” Acta Materialia, 50 (2002) 4419.

    134

    125

    1. R. S. Mishra, Z. Y. Ma and I. Charit, “Friction stir processing: A novel technique for fabrication of surface composite,” Materials Science and Engineering A, A341 (2003) 307.

    114

    97

    1. P. B. Berbon, W. H. Bingel, R. S. Mishra, C. C. Bampton and M. W. Mahoney, “Friction stir processing: a tool to homogenize nanocomposite aluminum alloys,” Scripta Materialia, 44 (2001) 61.

    89

    84

    1. R. S. Mishra and M. W. Mahoney, “Friction stir processing: A new grain refinement technique to achieve high strain rate superplasticity in commercial alloys,” Superplasticity In Advanced Materials, ICSAM-2000 Materials Science Forum, 357-3 (2001) 507.

    80

    84

    1. R. S. Mishra, R. Z. Valiev, S. X. McFadden and A. K. Mukherjee, “Tensile Superplasticity in Nanocrystalline Nickel Aluminide” Materials Science and Engineering A, A252 (1998) 174.

    80

    83

    1. R. S. Mishra, R. Z. Valiev, S. X. McFadden, R. K. Islamgaliev and A. K. Mukherjee, “High strain rate superplasticity from nanocrystalline Al alloy 1420 at low temperatures,” Philosophical Magazine A, 81 (2001) 37.

    73

    71

    1. R. S. Mishra and A. B. Pandey, "Some observations on the high-temperature creep behaviour of 6061 Al-SiC composites," Metallurgical Transactions A, 21A (1990) 2089.

    73

    99

    1. I. Charit and R. S. Mishra, “High strain rate superplasticity in a commercial 2024 Al alloy via friction stir processing,” Materials Science and Engineering A, A359 (2003) 290.

    72

    70

    1. R. S. Mishra, T. R. Bieler and A. K. Mukherjee, “Mechanism of high strain rate superplasticity in aluminum alloy composites,” Acta Metallurgica et Materialia., 45 (1997) 561.

    70

    65

    1. R. S. Mishra, C. E. Lesher and A. K. Mukherjee, “High pressure sintering of nanocrystalline -Al2O3,” J. American Ceramic Society, 79 (1996) 2989.

    66

    66

    1. R. S. Mishra, V. V Stolyarov, C. Echer, R. Z. Valiev, A. K. Mukherjee, “Mechanical behavior and superplasticity of a severe plastic deformation processed nanocrystalline Ti-6Al-4V alloy,” Materials Science and Engineering, A298 (2001) 44.

    57

    51

    1. R. S. Mishra, J. Schneider, J. F. Shackelford and A. K. Mukherjee, "Plasma activated sintering of nanocrystalline -Al2O3," NanoStructured Materials, 5 (1995) 525.

    55

    52

    1. S. Ranganath and R. S. Mishra, "Steady state creep behavior of particulate reinforced titanium matrix composites," Acta Metallurgica et Materialia, 44 (1996) 927.

    52

    56

    1. Z. Y. Ma, R. S. Mishra, M. W. Mahoney, and R. Grimes, “High strain rate superplasticity in friction stir processed Al-Mg-Zr alloy,” Materials Science and Engineering A, A351 (2003) 148.

    51

    46

    1. S. R. Sharma, Z. Y. Ma and R. S. Mishra, “Effect of friction stir processing on fatigue behavior of A356 alloy,” Scripta Materialia, 51 (2004) 237.

    48

    43

    1. I. Charit, R. S. Mishra and M. W. Mahoney, “Multi-sheet structures in 7475 aluminum by friction stir welding in concert with post-weld superplastic forming,” Scripta Materialia, 47 (2002) 631.

    47

    44

    1. Z. Y. Ma, R. S. Mishra and M. W. Mahoney, “Superplasticity in cast A356 induced via friction stir processing,” Scripta Materialia, 50 (2004) 931.

    46

    41

    1. A. B. Pandey, R. S. Mishra and Y. R. Mahajan, "High temperature creep of Al-TiB2 particulate composites," Materials Science and Engineering A, A189 (1994) 95.

    45

    46

    1. A. B. Pandey, R. S. Mishra and Y. R. Mahajan, "Creep behaviour of an aluminium-silicon carbide particulate composite," Scripta Metallurgica, 24 (1990) 1565.

    45

    56


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