A Review of Different Creep Mechanisms in Mg Alloys Based on Stress Exponent and Activation Energy

Athul, Karuna Ratnakaran; Pillai, U.T.S.; Srinivasan, A.; Pai, B.C.

doi:10.1002/adem.201500393

Cited by 78 publications

(26 citation statements)

References 102 publications

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“…However, any interpretation solely based on microstructure fails to explain the observed improvement in the creep lifetime in Mg–Nd–Zn. Reasonable explanations must also consider vacancy interaction with precipitates and solutes, and acceleration of dislocation climb over impeding precipitates, driven by enhanced vacancy diffusion at high homologous temperature, and activated cross-slip of screw dislocations 10 – 13 .…”

Section: Resultsmentioning

confidence: 99%

“…Stress–temperature combinations that cause creep in Mg alloys during service, e.g., in automotive engine, powertrain applications for example, largely occur via dislocation climb, activated cross-slip, and/or grain boundary sliding 10 – 13 . Consequently, in the case of Mg alloys, the strategy for precipitation hardening typically selects alloying elements (with lower solubility in Mg, e.g., rare earth elements 10 , 18 ) that form precipitates in high number densities on the dominant slip systems 20 – 22 .…”

Section: Introductionmentioning

confidence: 99%

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Exceptional increase in the creep life of magnesium rare-earth alloys due to localized bond stiffening

et al. 2017

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Several recent papers report spectacular, and unexpected, order of magnitude improvement in creep life of alloys upon adding small amounts of elements like zinc. This microalloying effect raises fundamental questions regarding creep deformation mechanisms. Here, using atomic-scale characterization and first principles calculations, we attribute the 600% increase in creep life in a prototypical Mg–rare earth (RE)–Zn alloy to multiple mechanisms caused by RE–Zn bonding—stabilization of a large volume fraction of strengthening precipitates on slip planes, increase in vacancy diffusion barrier, reduction in activated cross-slip, and enhancement of covalent character and bond strength around Zn solutes along the c-axis of Mg. We report that increased vacancy diffusion barrier, which correlates with the observed 25% increase in interplanar bond stiffness, primarily enhances the high-temperature creep life. Thus, we demonstrate that an approach of local, randomized tailoring of bond stiffness via microalloying enhances creep performance of alloys.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exceptional increase in the creep life of magnesium rare-earth alloys due to localized bond stiffening

et al. 2017

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“…Under steady-state creep condition, the steadystate creep rate, _ e s , can be described as a function of stress, r, and temperature, T, at elevated temperatures: 18 _ e s ¼ Ar n exp À Q=RT ð Þ ð 1Þ where A is a dimensionless material constant, n is the stress exponent, Q is the activation energy for creep and R is the gas constant. At a given temperature, most of the creep deformations of polycrystalline alloys follow a power-law relationship: _ e s ¼ kr n ð2Þ where k is a constant.…”

Section: Resultsmentioning

confidence: 99%

The Role of Second Phases on the Creep Behavior of As-Cast and Hot-Extruded Mg-Ca-Zr Alloys

You

Huang

Dieringa

et al. 2019

JOM

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The effect of second phases on the creep behavior of Mg-Ca-Zr alloys was investigated. Casting and hot-extrusion processes were performed to prepare Mg-xCa-0.5Zr (x = 0 wt.%, 0.3 wt.% and 0.6 wt.%) alloys with different morphologies and distributions of second phases. The as-cast microstructures of Mg-Ca-Zr alloys consisted of an Mg matrix and coarse Mg 2 Ca intermetallic compounds distributed at the grain boundaries. The hot-extruded microstructures exhibited finer Mg 2 Ca spherical particles and precipitates distributed homogeneously inside the matrix and along the grain boundaries. The results of creep tests suggested that the viscous glide of dislocation and dislocation climb were the dominant creep mechanisms of Mg-Ca-Zr alloys crept at 200°C. The creep property was strongly related to the morphology and distribution of the Mg 2 Ca phases. The finer and more homogeneously distributed particles showed a better strengthening effect than the coarser intermetallic compounds distributed along the grain boundaries.

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“…(1) the standard load transducer (2) high load transduce (3), optical camera and (4) [42,46]; (c) to determine the activation volume V*; (d) The activation volume V* as a function of Zn content from current work and in [44]. [132,133]. [2-1-10] zone axis with diffraction vector g1= [1][2][3][4][5][6][7][8][9][10][11][12]; [1-21-3] zone axis with (b) g2= [1101]; (c) g3= [1][2][3][4][5][6][7][8][9][10][11] and (d) g= [1][2][3][4][5][6][7][8][9][10][11].…”

Section: Fig 312: Fib-based Lift-out Process and Annular Milling Fomentioning

confidence: 99%

High-throughput screening of strength and creep properties in Mg-Zn alloys

Li¹

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Looking back to the four years and three months that my Ph.D. journey took at IMDEA Materials Institute and the Polytechnic University of Madrid, I wish to express my sincerest and deepest gratitude to many people who offered me their support and help since the first day I arrived at IMDEA. First of all, I would like to express my most sincere gratitude to my supervisor Dr. Jon Molina. We did not even have a Skype meeting before and we only met after two months since I arrived at IMDEA. Thanks for your trust, for providing me with the opportunity to work in your group and for guiding me fully and patiently along this journey. At the beginning, I was new to the nanomechanical field, but you explained patiently the fundamental theory to me and checked the work carefully during each meeting. Gradually, you gave me a lot of freedom and your passion encouraged me to get deeper and deeper into the field. You helped me overcoming the difficulties and avoiding the mistakes that we often make when we work in a quick, eager and impetuous way, without deeper thinking. I still remember one day clearly, when you made me realize how natural aging at room temperature could influence the results on supersaturated Mg-Zn solid solutions. This made us introduce the topic of Zn distribution by studying the diffusion couple in the as-quenched, room aged and peak aged conditions. I also want to thank you for teaching me to think in a critical way, to improve my scientific writing and to help me differentiate between experimental evidence and mere speculation. Many thanks for all your wisdom guidance and continuous encouragement to help me grow during my study and work at IMDEA. Without your scholarly inputs and valuable guidance, this thesis would have not been possible. Your passion and solid background in materials science inspire me to continue working on materials research in the future. I feel so grateful and fortunate for having been working under your supervision and for growing up in our pleasant and exciting group. I also own my most sincere thanks to my other supervisor, Dr. Yuwen Cui, with whom I worked since I joined IMDEA Materials. Despite your departure one year later to Nanjing Tech University, you have remained deeply involved in my thesis. Your guidance, great patience and insightful vision was essential to introduce me in the field of high-throughput development of Mg alloys. I also wish to thank IMDEA Materials Institute for offering me such a fantastic environment for scientific research. I'm grateful for the financial support from the China Scholarship Council. My special thanks go to my colleagues: Dr. Miguel Monclus, thanks for your assistance with performing nanomechanical tests, which were always very timeconsuming; and Dr. Miguel Castillo, thanks for your help with the TEM characterizations and for training in the FIB. Special thanks to Dr. Lingwei Yang and Dr. Chuanyun Wang. You two taught and helped me a lot in micropillar testing and TEM lamellar preparation and also helped me analyse the data even during...

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A Review of Different Creep Mechanisms in Mg Alloys Based on Stress Exponent and Activation Energy

Cited by 78 publications

References 102 publications

Exceptional increase in the creep life of magnesium rare-earth alloys due to localized bond stiffening

Exceptional increase in the creep life of magnesium rare-earth alloys due to localized bond stiffening

The Role of Second Phases on the Creep Behavior of As-Cast and Hot-Extruded Mg-Ca-Zr Alloys

High-throughput screening of strength and creep properties in Mg-Zn alloys

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