Polikristal FeNiCrCoCu Yüksek Entropili Alaşımının Mukavemet-Süneklik Davranışına Tane Büyüklüğünün Etkisi

Öz

Polikristal nano tel FeNiCrCoCu yüksek entropili alaşımının (YEA) mukavemet-süneklik davranışına tane büyüklüğünün etkisi moleküler dinamik (MD) benzetimi kullanılarak 300 K sıcaklık değerinde model sisteme tek eksenli çekme deformasyonu uygulanarak incelendi. Gömülmüş Atom Metodu (GAM), model sistemdeki atomlar arası kuvvetlerin belirlenmesinde kullanıldı. Tane büyüklüğünün mukavemet-süneklik, Young modülü, akma gerilimi, kopma ve boyun verme gerinimi değerleri üzerinde etkili olduğu belirlendi. Farklı tane büyüklüklerine sahip YEA model sistemlerin hepsinin uygulanan çekme deformasyon işlemi sonucu yüksek süneklik gösterdiği tespit edildi. Ortak komşu analiz yöntemi (Common Neighbor Analysis-CNA) kullanılarak YEA sistemindeki mikro yapısal değişimler ve deformasyon mekanizmaları incelendi. Gerilim-gerinim analizleri sonucu tane boyutunun kritik bir eşik değerinin üzerinde, model sistemde Hall-Petch (HP) güçlendirmesinin hâkim olduğu, ancak bu kritik boyutun altındaki ince taneli yapılarda ise ters HP davranışı tespit edildi. Mukavemet-süneklik arasındaki ilişkide tane büyüklüğünün ve bunun sonucunda farklı plastik deformasyon mekanizmalarının önemli bir etkiye sahip olduğu belirlendi. Özellikle deformasyon ikizleri, yüksek mukavemet ile yüksek sünekliğin aynı anda sağlanmasında belirleyici bir rol oynamaktadır. Bu sonuçlar, FeNiCrCoCu model alaşım sisteminin hem yüksek mukavemet hem de yüksek süneklik sergileyen etkili bir mekanik performansa sahip olduğunu ve tane mühendisliğinin yüksek performanslı YEA’ların tasarımında büyük bir öneme sahip olduğunu göstermektedir.

Anahtar Kelimeler

• Yüksek entropili alaşım
• Polikristal
• Süneklik
• Moleküler dinamik
• Hall-Petch

Effect of Grain Size on the Strength-Ductility Behavior of Polycrystalline FeNiCrCoCu High Entropy Alloy

Öz

The effect of grain size on the strength-ductility behavior of polycrystalline nanowire FeNiCrCoCu high-entropy alloy (HEA) was investigated using molecular dynamics (MD) simulation by applying uniaxial tensile deformation to the model system at a temperature of 300 K. The Embedded Atom Method (EAM) was used to determine the interatomic forces in the model system. Grain size was found to influence the strength–ductility relationship, Young’s modulus, yield stress, fracture strain, and necking strain values. In addition, all HEA model systems with different grain sizes exhibited high ductility under the applied tensile deformation. The microstructural changes and deformation mechanisms in the HEA system were investigated using the Common Neighbor Analysis (CNA) method. Stress-strain analyses revealed that above a critical threshold of grain size, Hall-Petch (HP) reinforcement predominated in the model system, but in fine-grained structures below this critical size, the inverse HP behavior was observed. It was determined that grain size and, consequently, different plastic deformation mechanisms have a significant effect on the relationship between strength and ductility. Deformation twins, in particular, play a crucial role in achieving both high strength and high ductility simultaneously. These results demonstrate that the FeNiCrCoCu model alloy system exhibits high mechanical performance, combining high strength and ductility, and highlight the significant importance of grain engineering in the design of high-performance HEAs.

Anahtar Kelimeler

• High entropy alloys
• Polycrystalline
• High ductility
• Molecular dynamics
• Hall-Petch

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