MDPI - Publisher of Open Access Journals

17 pages, 7169 KiB

Open AccessArticle

Structural Evolution, Mechanical Properties, and Thermal Stability of Multi-Principal TiZrHf(Ta, Y, Cr) Alloy Films

by Yung-I Chen, Tzu-Yu Ou, Li-Chun Chang and Yan-Zhi Liao

Materials 2025, 18(15), 3672; https://doi.org/10.3390/ma18153672 - 5 Aug 2025

Mixing enthalpy (ΔH_mix), mixing entropy (ΔS_mix), atomic-size difference (δ), and valence electron concentration (VEC) are the indicators determining the phase structures of multi-principal element alloys. Exploring the relationships between the structures and properties of multi-principal element films is a fundamental study. TiZrHf films with a ΔH_mix of 0.00 kJ/mol, ΔS_mix of 9.11 J/mol·K (1.10R), δ of 3.79%, and VEC of 4.00 formed a hexagonal close-packed (HCP) solid solution. Exploring the characterization of TiZrHf films after solving Ta, Y, and Cr atoms with distinct atomic radii is crucial for realizing multi-principal element alloys. This study fabricated TiZrHf, TiZrHfTa, TiZrHfY, and TiZrHfCr films through co-sputtering. The results indicated that TiZrHfTa films formed a single body-centered cubic (BCC) solid solution. In contrast, TiZrHfY films formed a single HCP solid solution, and TiZrHfCr films formed a nanocrystalline BCC solid solution. The crystallization of TiZrHf(Ta, Y, Cr) films and the four indicators mentioned above for multi-principal element alloy structures were correlated. The mechanical properties and thermal stability of the TiZrHf(Ta, Y, Cr) films were investigated. Full article

(This article belongs to the Section Thin Films and Interfaces)

► Show Figures

Figure 1

10 pages, 2561 KiB

Open AccessArticle

Estimation of Shear Modulus and Hardness of High-Entropy Alloys Made from Early Transition Metals Based on Bonding Parameters

by Ottó Temesi, Lajos K. Varga, Xiaoqing Li, Levente Vitos and Nguyen Q. Chinh

Materials 2023, 16(6), 2311; https://doi.org/10.3390/ma16062311 - 13 Mar 2023

Cited by 4 | Viewed by 2410

Abstract

The relationship between the tendencies towards rigidity (measured by shear modulus, G) and hardness (measured by Vickers hardness, HV) of early transition metal (ETM)-based refractory high-entropy alloys (RHEA) and bond parameters (i.e., valence electron concentration (VEC), enthalpy of mixing (ΔH_mix)) was investigated. These bond parameters, VEC and ΔH_mix, are available from composition and tabulated data, respectively. Based on our own data (9 samples) and those available from the literatures (47 + 27 samples), it seems that for ETM-based RHEAs the G and HV characteristics have a close correlation with the bonding parameters. The room temperature value of G and HV increases with the VEC and with the negative value of ΔH_mix. Corresponding equations were deduced for the first time through multiple linear regression analysis, in order to help design the mechanical properties of ETM refractory high-entropy alloys. Full article

(This article belongs to the Special Issue Advances in High Entropy Materials)

► Show Figures

Figure 1

13 pages, 9572 KiB

Open AccessFeature PaperArticle

A Strategic Design Route to Find a Depleted Uranium High-Entropy Alloy with Great Strength

by Weiran Zhang, Yasong Li, Peter K. Liaw and Yong Zhang

Metals 2022, 12(4), 699; https://doi.org/10.3390/met12040699 - 18 Apr 2022

Cited by 8 | Viewed by 3226

Abstract

The empirical parameters of mixing enthalpy (ΔH_mix), mixing entropy (ΔS_mix), atomic radius difference (δ), valence electron concentration (VEC), etc., are used in this study to design a depleted uranium high-entropy alloy (HEA). X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to assess the phase composition. Compression and hardness tests were conducted to select alloy constituents with outstanding mechanical properties. Based on the experimental results, the empirical criteria of HEAs are an effective means to develop depleted uranium high-entropy alloys (DUHEAs). Finally, we created UNb_0.5Zr_0.5Mo_0.5 and UNb_0.5Zr_0.5Ti_0.2Mo_0.2 HEAs with outstanding all-round characteristics. Both alloys were composed of a single BCC structure. The hardness and strength of UNb_0.5Zr_0.5Mo_0.5 and UNb_0.5Zr_0.5Ti_0.2Mo_0.2 were 305 HB and 1452 MPa, and 297 HB and 1157 MPa, respectively. Full article

(This article belongs to the Special Issue Amorphous and High-Entropy Alloy Coatings)

► Show Figures

Figure 1

8 pages, 4419 KiB

Open AccessArticle

The Microalloying Effect of Ce on the Mechanical Properties of Medium Entropy Bulk Metallic Glass Composites

by Yanchun Zhao, Pengbiao Zhao, Wensheng Li, Shengzhong Kou, Jianlong Jiang, Xuejing Mao and Zhuang Yang

Crystals 2019, 9(9), 483; https://doi.org/10.3390/cryst9090483 - 15 Sep 2019

Cited by 11 | Viewed by 2971

Abstract

Novel ultra-strong medium entropy bulk metallic glasses composites (BMGCs) Fe_65.4−xCe_xMn_14.3Si_9.4Cr₁₀C_0.9 and Ti_40−xCe_xNi₄₀Cu₂₀ (x = 0, 1.0), through the martensite transformation induced plasticity (TRIP effect) to enhance both the ductility and work-hardening capability, were fabricated using magnetic levitation melting and copper mold suction via high frequency induction heating. Furthermore, the Ce microalloying effects on microstructure and mechanical behaviors were studied. The Fe-based BMGCs consisted of face-centered cubic (fcc) γ-Fe and body-centered cubic (bcc) α-Fe phase, as well as Ti-based BMGCs containing supercooled B2-Ti (Ni, Cu) and a thermally induced martensite phase B19’-Ti (Ni, Cu). As loading, the TRIP BMGCs exhibited work-hardening behavior, a high fracture strength, and large plasticity, which was attributed to the stress-induced transformation of ε-Fe martensite and B19’-Ti (Ni, Cu) martensite. Ce addition further improved the strengthening and toughening effects of TRIP BMGCs. Adding elemental Ce enhanced the mixing entropy ΔS_mix and atomic size difference δ, while reducing the mixing enthalpy ΔH_mix, thus improving the glass forming ability and delaying the phase transition process, and hence prolonging the work-hardening period before fracturing. The fracture strength σ_f and plastic stress ε_p of Ti₃₉CeNi₄₀Cu₂₀ and Fe_64.4CeMn_14.3Si_9.4Cr₁₀C_0.9 alloys were up to 2635 MPa and 13.8%, and 2905 MPa and 30.1%, respectively. Full article

(This article belongs to the Special Issue Advanced High Temperature Shape Memory Alloys)

► Show Figures

Figure 1

Search Results (4)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (4)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI