Investigation on Additional Hardening Mechanisms in Off-Stoichiometric Al-Rich Ni3Al Alloys in Terms of Anti-Site Defect Configuration

2002 ◽  
Vol 753 ◽  
Author(s):  
Seiji Miura ◽  
Satoshi Takizawa ◽  
Yoshinao Mishima ◽  
Tetsuo Mohri
Keyword(s):  
Flow Stress ◽  
Stoichiometric Composition ◽  
Strengthening Mechanism ◽  
Size Difference ◽  
Atomic Size ◽  
Hardening Mechanism ◽  
Atomic Size Difference ◽  
Hardening Mechanisms ◽  
Rich Side ◽  
Additional Hardening

ABSTRACTOne of the unsettled issues of the mechanical properties of L12-Ni3Al compound is the effect of off-stoichiometry on the 0.2% flow stress at low temperature region. 0.2% flow stress at 77 K increases as deviating from the stoichiometric composition to both Ni-rich and Al-rich sides, but in Al-rich side the increasing rate is higher. According to the XRD results for the binary Ni3Al alloys, however, the composition dependence of the lattice constant is the same in both sides of the stoichiometric composition, which implies that the magnitude of lattice strain induced at off-stoichiometric composition is symmetrical. And it is not rational to associate the strengthening mechanism to a sole effect of isotropic strain due to an atomic size difference. In this study, attempts are made to explain the additional strengthening in Al-rich alloys in terms of the tetragonal distortion hardening mechanism, which arises from anisotropic atomic configuration around an anti-site Al atom.

scholarly journals Phase selection motifs in High Entropy Alloys revealed through combinatorial methods: Large atomic size difference favors BCC over FCC

2019 ◽  
Vol 166 ◽  
pp. 677-686 ◽  
Author(s):  
Sebastian Alexander Kube ◽  
Sungwoo Sohn ◽  
David Uhl ◽  
Amit Datye ◽  
Apurva Mehta ◽  
...  
Keyword(s):  
Size Difference ◽  
High Entropy Alloys ◽  
Atomic Size ◽  
Phase Selection ◽  
High Entropy ◽  
Atomic Size Difference ◽  
Combinatorial Methods

Reassessing the atomic size effect on glass forming ability: Effect of atomic size difference on thermodynamics and kinetics

2016 ◽  
Vol 69 ◽  
pp. 123-127 ◽  
Author(s):  
Hyung-Seop Han ◽  
Nayoung Park ◽  
Jin-Yoo Suh ◽  
Ho-Seok Nam ◽  
Hyun-Kwang Seok ◽  
...  
Keyword(s):  
Size Effect ◽  
Glass Forming Ability ◽  
Size Difference ◽  
Atomic Size ◽  
Glass Forming ◽  
Thermodynamics And Kinetics ◽  
Atomic Size Difference

Atomic Size Effects on the Composition Range of Binary Amorphous Alloys

1986 ◽  
Vol 80 ◽  
Author(s):  
S. H. Liou ◽  
C. L. Chien
Keyword(s):  
Size Effects ◽  
Amorphous Alloys ◽  
Composition Range ◽  
Equilibrium Phase ◽  
Size Difference ◽  
Atomic Size ◽  
Atomic Size Difference ◽  
Metal Metal ◽  
Quench Method

AbstractWe have studied a number of binary metal-metal and metalloid alloy systems made by a single vapor quench method under very consistent conditions. In each case, amorphous alloys are found in one continuous composition range (Xmin<x<xXmax) regardless of the number of eutectic points in the equilibrium phase diagrams. It is found that the atomic size difference is the single most important factor in the quantitative determination of the composition range.

scholarly journals Effect of Atomic Size Difference on the Microstructure and Mechanical Properties of High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 967 ◽  
Author(s):  
Chan-Sheng Wu ◽  
Ping-Hsiu Tsai ◽  
Chia-Ming Kuo ◽  
Che-Wei Tsai
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Grain Growth ◽  
Size Difference ◽  
High Entropy Alloys ◽  
Atomic Size ◽  
High Entropy ◽  
Microstructure And Mechanical Properties ◽  
Atomic Size Difference ◽  
Fcc Phase

The effects of atomic size difference on the microstructure and mechanical properties of single face-centered cubic (FCC) phase high-entropy alloys are studied. Single FCC phase high-entropy alloys, namely, CoCrFeMnNi, Al0.2CoCrFeMnNi, and Al0.3CoCrCu0.3FeNi, display good workability. The recrystallization and grain growth rates are compared during annealing. Adding Al with 0.2 molar ratio into CoCrFeMnNi retains the single FCC phase. Its atomic size difference increases from 1.18% to 2.77%, and the activation energy of grain growth becomes larger than that of CoCrFeMnNi. The as-homogenized state of Al0.3CoCrCu0.3FeNi high-entropy alloy becomes a single FCC structure. Its atomic size difference is 3.65%, and the grain growth activation energy is the largest among these three kinds of single-phase high-entropy alloys. At ambient temperature, the mechanical properties of Al0.3CoCrCu0.3FeNi are better than those of CoCrFeMnNi because of high lattice distortion and high solid solution hardening.

Solid Solution Formation Criteria for High Entropy Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 1337-1339 ◽  
Author(s):  
Yong Zhang ◽  
Yun Jun Zhou
Keyword(s):  
Solid Solution ◽  
Enthalpy Of Mixing ◽  
Atomic Ratio ◽  
Size Difference ◽  
Atomic Size ◽  
Solid Solution Formation ◽  
Absolute Value ◽  
High Entropy ◽  
Solution Formation ◽  
Atomic Size Difference

The solid solution formation criteria for the equi-atomic ratio alloys were discussed. It is found that higher entropy of mixing (Smix>1.61R), less atomic size difference (δ<4.6), and near zero of the absolute value of the enthalpy of mixing (-2.685δ-2.54<Hmix <-1.28δ+5.44 KJ/mol) facilitate the formation of solid solution for the multi-principle components equi-atomic alloys.

Crystal to Glass Transition and Melting in Two Dimensions

1993 ◽  
Vol 321 ◽  
Author(s):  
M. Li ◽  
W. L. Johnson ◽  
W. A. Goddard
Keyword(s):  
Glass Transition ◽  
Intermediate Phase ◽  
Orientational Order ◽  
Finite Size ◽  
Two Dimensions ◽  
Size Difference ◽  
Two Dimensional ◽  
Atomic Size ◽  
Bond Orientational Order ◽  
Dynamics Simulations

ABSTRACTThermodynamic properties, structures, defects and their configurations of a two-dimensional Lennard-Jones (LJ) system are investigated close to crystal to glass transition (CGT) via molecular dynamics simulations. The CGT is achieved by saturating the LJ binary arrays below glass transition temperature with one type of the atoms which has different atomic size from that of the host atoms. It was found that for a given atomic size difference larger than a critical value, the CGT proceeds with increasing solute concentrations in three stages, each of which is characterized by distinct behaviors of translational and bond-orientational order correlation functions. An intermediate phase which has a quasi-long range orientational order but short range translational order has been found to exist prior to the formation of the amorphous phase. The destabilization of crystallinity is observed to be directly related to defects. We examine these results in the context of two dimensional (2D) melting theory. Finite size effects on these results, in particular on the intermediate phase formation, are discussed.

Defect Structure of β NiAl Using the BFS Method for Alloys

1995 ◽  
Vol 408 ◽  
Author(s):  
Guillermo Bozzolo ◽  
Carlos Amador ◽  
John Ferrante ◽  
Ronald D Noebe
Keyword(s):  
Point Defects ◽  
Stoichiometric Composition ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
New Approach ◽  
Al Content ◽  
Steep Decrease ◽  
Basic Features ◽  
And Behavior ◽  
Rich Side

AbstractThe semiempirical BFS method for alloys is generalized by replacing experimental input with firstprinciples results thus allowing for the study of complex systems. In order to examine trends and behavior of a system in the vicinity of a given point of the phase diagram a search procedure based on a sampling of selected configurations is employed. This new approach is applied to the study of the/3 phase of the Ni-Al system, which exists over a range of composition from 45–60 at. % Ni. This methodology results in a straightforward and economical way of reproducing and understanding the basic features of this system. At the stoichiometric composition, NiAl should exist in a perfectly ordered B2 structure. Ni-rich alloys are characterized by antisite point defects (with Ni atoms in the Al sites) with a decrease in lattice parameters. On the Al-rich side of stoichiometry there is a steep decrease in lattice parameter and density with increasing Al content. The presence of vacancies in Ni sites would explain such behavior. Recent X-ray diffraction experiments suggest a richer structure: the evidence, while strongly favoring the presence of vacancies in Ni sites, also suggests the possibility of some vacancies in Al sites in a 3:1 ratio. Moreover, local ordering of vacant sites may be preferred over a random distribution of individual point defects.

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