Influence of Annealing on Microstructure and Mechanical Properties of Refractory CoCrMoNbTi 0.4 High-Entropy Alloy

  • PDF / 2,787,891 Bytes
  • 15 Pages / 593.972 x 792 pts Page_size
  • 6 Downloads / 289 Views

DOWNLOAD

REPORT


NTRODUCTION

HIGH-ENTROPY alloys (HEAs) have attracted extensive research attention owing to their unique phase constitutes and excellent properties.[1] This new generation of alloy is composed of at least five principal components in equal or close-to-equal atomic percentages, which violates the design concept of conventional alloy, which are based on one or two major elements as their principal constituents. Owing to the high mixing entropy effect, HEAs are favorable for the formation of simple solid solution phases of body-centered cubic (BCC), face-centered cubic (FCC), and/or hexagonal close-packed (HCP) structures.[2–4] In the past several years, considerable experimental results revealed that HEAs exhibit unique performance, such as exceptional thermal stability, high hardness, high strength, outstanding wear resistance, and corrosion resistance, attributed to a combination of special structural and compositional characteristics.[5–8] Thus, HEAs are considered to be a viable alternative to conventional

MINA ZHANG, XIANGLIN ZHOU, WUZHI ZHU, and JINGHAO LI are with the State Key Laboratory for Advance Metals and Materials, University of Science and Technology Beijing, Beijing 10083, People’s Republic of China Contact e-mail: [email protected] Manuscript submitted August 25, 2017.

METALLURGICAL AND MATERIALS TRANSACTIONS A

high-temperature structural materials in various potential applications. Among all reported HEAs, a novel class of HEA systems—refractory HEAs composed of refractory metallic elements—has triggered significant interest to date.[9–11] As already reported in the literature, most refractory HEAs usually form a single solid solution structure and exhibit intriguing elevated-temperature properties. These advantages render refractory HEAs particularly attractive for elevated-temperature applications. For example, a series of novel refractory HEAs with a single-phase BCC structure—NbMoTaW, NbMoTaWV, and TaNbHfZrTi—were first proposed by Senkov et al.[12–14] NbMoTaW and NbMoTaWV exhibit high compression yield strengths up to 405 and 477 MPa at 1873 K (1600 C), respectively, which are much superior to those of most of the existing Ni-based superalloy at high temperature [> 1273 K (1000 C)]. The strength of refractory HEAs at high temperature is attributed not only to the higher melting temperature of their constitutive elements but also the solid-solution-like strengthening.[13] However, the two refractory alloy has high densities—13.75 g/cm3 for NbMoTaW and 12.36 g/cm3 for NbMoTaWV. Subsequently, another refractory HEA, TaNbHfZrTi alloy with a reduced density of q = 9.94 g/cm3, was produced by replacing heavier elements (W, Mo, and V) with lighter elements (Hf, Zr, and Ti). This type of alloy under the as-casting and hot isostatic pressing (HIP) conditions

shows higher compression yield strength (929 MPa) and ductility (e > 50 pct) at room temperature. Unfortunately, its strength at high temperatures rapidly decreases to less than 100 MPa [yield strength = 92 MPa at 1473 K (1200 C)], which may limi

Data Loading...