高熵合金简介
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P is number of phases
Why high entropy effect can simplify the microstructures?
High mixing entropy enhances the mutual solubility among elements, and prevents phase separation into ordered phases or intermetallic compounds.
BCC
FCC
The number of phases is far lower than the maximum
F = C – P + 1 …. The Gibbs phase rule
P = C + 1 F is degree of freedom, C is number of components, and
mix
When entropy increase, Gibbs free energy decrease.
Some intermetallic phases can form in some HE alloys.
Strong bonding between some metallic elements will cause very large heats of formation, so enthalpy can play a more important role.
[5] 維基百科, http://zh.wikipedia.org
Introduction Four major effects Strengthening Mechanism Other features Applications Conclusions
In 1995, the multi-principal-element alloys termed as high-entropy alloys are brought up, which emphasizes their inherent high mBiblioteka Baiduxing entropies.
The high entropy effect plays an important role in simplifying the microstructures.
Form solid solution phases
Such as BCC and FCC rather than ordered phases or intermetallic compounds.
There is high entropy in the alloys.
5 to 13 principle elements (5%≦X≦35%) in the alloys.
The number of alloy systems (7099) are greater than conventional alloys(30).
The lower limit of 5 elements is imposed.
△Smix is high enough to counterbalance the △Hmix
△Gmix = △Hmix -T△Smix
T△S △H mix play an important role than
[2] Jien-Wei YEH, Recent progress in high-entropy alloys, 2006.
[3] Jien-Wei YEH, 從高熵合金探討未來金屬材料發展趨勢, 2006.
[4] Y.J. Zhou , Y. Zhang , T.N. Kim , G.L. Chen, Microstructure characterizations and strengthening mechanism of multi-principal component AlCoCrFeNiTi0.5 solid solution alloy with excellent mechanical properties, 2008.
The high entropy of HE alloy significantly lowers the free energy thus lowering its tendency to order and segregate(solubility ↑) , making solid solution more easily form and more stable than intermetallics or other ordered phases during solidification in this alloys, especially at high temperature.
Having four major effects.
‧ 熱力學上 - High entropy effect (高熵效應) ‧ 動力學上 - Sluggish diffusion effect (遲緩擴散效應) ‧ 晶體結構上 - Lattice distortion effect (晶格扭曲效應) ‧ 性質上 - Cocktail effect (雞尾酒效應)
Such as strong ceramic compounds: Oxides (氧化物), Carbides (碳化物), Nitrides(氮化物), and Silicides (矽化物).
The simple introduction of new century
High Entropy Alloys (HE alloys)
With Multiple Principal Elements
[1] Yeh JW, Chen SK, Lin SJ, Gan JY, Chin TS, Shun TT, Tsau CH, Chang SY, nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts And Outcomes, 2004.
Why high entropy effect can simplify the microstructures?
High mixing entropy enhances the mutual solubility among elements, and prevents phase separation into ordered phases or intermetallic compounds.
BCC
FCC
The number of phases is far lower than the maximum
F = C – P + 1 …. The Gibbs phase rule
P = C + 1 F is degree of freedom, C is number of components, and
mix
When entropy increase, Gibbs free energy decrease.
Some intermetallic phases can form in some HE alloys.
Strong bonding between some metallic elements will cause very large heats of formation, so enthalpy can play a more important role.
[5] 維基百科, http://zh.wikipedia.org
Introduction Four major effects Strengthening Mechanism Other features Applications Conclusions
In 1995, the multi-principal-element alloys termed as high-entropy alloys are brought up, which emphasizes their inherent high mBiblioteka Baiduxing entropies.
The high entropy effect plays an important role in simplifying the microstructures.
Form solid solution phases
Such as BCC and FCC rather than ordered phases or intermetallic compounds.
There is high entropy in the alloys.
5 to 13 principle elements (5%≦X≦35%) in the alloys.
The number of alloy systems (7099) are greater than conventional alloys(30).
The lower limit of 5 elements is imposed.
△Smix is high enough to counterbalance the △Hmix
△Gmix = △Hmix -T△Smix
T△S △H mix play an important role than
[2] Jien-Wei YEH, Recent progress in high-entropy alloys, 2006.
[3] Jien-Wei YEH, 從高熵合金探討未來金屬材料發展趨勢, 2006.
[4] Y.J. Zhou , Y. Zhang , T.N. Kim , G.L. Chen, Microstructure characterizations and strengthening mechanism of multi-principal component AlCoCrFeNiTi0.5 solid solution alloy with excellent mechanical properties, 2008.
The high entropy of HE alloy significantly lowers the free energy thus lowering its tendency to order and segregate(solubility ↑) , making solid solution more easily form and more stable than intermetallics or other ordered phases during solidification in this alloys, especially at high temperature.
Having four major effects.
‧ 熱力學上 - High entropy effect (高熵效應) ‧ 動力學上 - Sluggish diffusion effect (遲緩擴散效應) ‧ 晶體結構上 - Lattice distortion effect (晶格扭曲效應) ‧ 性質上 - Cocktail effect (雞尾酒效應)
Such as strong ceramic compounds: Oxides (氧化物), Carbides (碳化物), Nitrides(氮化物), and Silicides (矽化物).
The simple introduction of new century
High Entropy Alloys (HE alloys)
With Multiple Principal Elements
[1] Yeh JW, Chen SK, Lin SJ, Gan JY, Chin TS, Shun TT, Tsau CH, Chang SY, nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts And Outcomes, 2004.