Alloying behavior and thermal stability of mechanically alloyed nano AlCoCrFeNiTi high-entropy alloy
- PDF / 987,939 Bytes
- 9 Pages / 584.957 x 782.986 pts Page_size
- 91 Downloads / 219 Views
FOCUS ISSUE
NANOCRYSTALLINE HIGH ENTROPY MATERIALS: PROCESSING CHALLENGES AND PROPERTIES
Alloying behavior and thermal stability of mechanically alloyed nano AlCoCrFeNiTi high-entropy alloy Vikas Shivam1,a)
, Yagnesh Shadangi1, Joysurya Basu1, Nilay Krishna Mukhopadhyay1
1
Department of Metallurgical Engineering, Indian Institute of Technology (BHU), Varanasi 221005, India Address all correspondence to this author. e-mail: [email protected]
a)
Received: 4 September 2018; accepted: 21 December 2018
In this investigation, we have reported the alloying behavior, phase evolution, and thermal stability of equiatomic AlCoCrFeNiTi high-entropy alloy (HEA). The 40 h milled powder shows good chemical homogeneity with agglomerated particles varying in the range of ∼3–18 lm. The formation of a nanostructured single-phase BCC (a = 2.85 ± 0.01 Å) was observed along with the minor tungsten carbide (WC) phase that formed due to contamination during milling. Thermal stability of the alloy has been studied using dynamic differential scanning calorimetry (DSC) thermogram and in situ X-ray diffraction. It has been found that this HEA is stable up to 600 °C (873 K). Consolidated samples at 1000 °C (1273 K) showed the transformation of body centered cubic (BCC) phase into the B2 (a = 2.87 ± 0.03 Å) phase co-existing with minor hexagonal WC (a = 2.90 Å, c = 2.83 Å) phase.
Introduction The design of the conventional alloys was primarily based on one or two principal alloying elements along with the addition of a few other minor elements to tailor the microstructures and their properties. The understanding of alloy design has been advanced by the seminal work of Cantor et al. [1] and Yeh et al. [2] by advocating a new class of materials, known as highentropy alloys (HEA). The name “high-entropy alloy” is justified due to higher mixing entropy compared with the conventional alloys for stabilizing the solid solution phase. This new class of alloys has received considerable attention due to its interesting novel properties compared with the conventional alloys [3]. HEAs generally should contain at least five principal alloying elements whose atomic concentration varies in the range of 5–35% [4]. Due to the presence of multi-principal elements, these alloys exhibit high-entropy (configurational) effect, favoring the formation of simple solid solution (body centered cubic (BCC)/face centered cubic (FCC)/hexagonal close packed (HCP)) phases [5]. A solid solution phase is understood to conform to the crystal structures resemble one of their parent structure in which the metal atoms are present in proportion to their concentration. However, the stability of the simple solid solution phases over a wide range of temperature is a major concern. It has been found that these simple solid
ª Materials Research Society 2019
solution phases can decompose into the other phases, including intermetallic phases, when exposed to prolonged heat treatment [6, 7]. HEAs possess good properties, i.e., high hardness, high strength, excellent thermal
Data Loading...
