Hydrogen embrittlement of C40 transition-metal disilicides
- PDF / 1,008,712 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 117 Downloads / 216 Views
Delin Pu1
1
School of Materials Science and Engineering, State Key Lab of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China a) Address all correspondence to this author. e-mail: [email protected] Received: 16 April 2019; accepted: 15 May 2019
The improvement of hydrogen embrittlement (HE) is a key problem for transition-metal silicides. Although C40 TMSi2 disilicides are attracted candidates for ultrahigh-temperature applications, the HE mechanism of TMSi2 is unclear. Importantly, the role of hydrogen on the structural configuration, elastic modulus, and hardness of TMSi2 is entirely unknown. To reveal the HE, we study the role of hydrogen in TMSi2 (TM = Nb, Mo, and W) based on the first-principles calculations. Four H-doped sites are considered in detail. The calculated results show that hydrogen is favorable to occupy the octahedral interstitial site because the C40 TMSi2 layered structure is favorable to absorb hydrogen. H-doping results in lattice expansion of c-axis compared with the aaxis and b-axis. H-doping obviously reduces the elastic modulus and hardness of TMSi2 due to the interaction between hydrogen and TMSi2. In addition, H-doping changes the electronic properties of MoSi2 and WSi2.
Introduction High-temperature structural materials are widely used in aeronautics and astronautics due to the high melting point, high-temperature strength, and excellent thermal stability [1, 2, 3, 4, 5, 6, 7, 8]. However, the harmful influence of hydrogen on the phases and the related mechanical properties of hightemperature structural materials severely hinders the development of the future high-temperature structural materials because hydrogen in high-temperature structural material destroys the cohesive force among atoms and thus results in hydrogen embrittlement (HE) [9, 10, 11, 12, 13, 14]. Therefore, the improvement of HE becomes a key problem for hightemperature structural material. To promote the development of high-temperature structural materials, it is necessary to reveal their mechanism of HE. In particular, we should explore the improvement of HE to meet the requirement of future high-temperature structural materials. Among the previously reported high-temperature structural materials, the hexagonal C40 transition metal disilicides (such as NbSi2, MoSi2, and WSi2) have received great attention because of their high melting point, superior mechanical properties, high thermal conductivity, excellent oxidation, and corrosion resistances etc. [15, 16, 17, 18, 19, 20, 21, 22,
ª Materials Research Society 2019
23, 24]. For example, the hexagonal C40 NbSi2 shows better oxidation resistance at the range of temperature (1000– 1450 °C) due to the formation of SiO2 particle [25, 26]. In particular, the first-principles calculations have shown that the calculated shear modulus, bulk modulus, and Young’s modulus of NbSi2 are 142 GPa, 174 GPa, and 335 GPa, respectively, which are larger than that of the other Nb–Si compounds [27]. The recent experimental works have sho
Data Loading...
