Suchergebnisse

In this study, 3D interconnected nanoporous (3DNP) TiVNbMoTa HEAs were synthesized from the (TiVNbMoTa)25Ni75 as-cast precursor alloy using the liquid metal dealloying (LMD). The as-cast precursor demonstrated the initial dendritic microstructure consisting of fcc and hcp phases. At 600 °C after 1 h, tiny ligaments about 10 nm thickness were homogeneously synthesized. At 900 °C, the bulk transformation intensively took place at the original precursor alloy. Specifically, the dendritic morphology of the original phases disappeared, and the fraction of fcc phase decreased from 63% to 20%. This pre-transformation behavior significantly influences the dealloying mechanism. Kurdjumov–Sachs orientation relationship (OR) governed the ligament formation at the prior fcc phase while Pitsch-Schrader (P–S) OR controlled the ligament evolution at the prior hcp phase. An unusual mechanism of two-step dealloying was observed at the fcc phase region when the dealloying rate was decreased at the reaction front. The dissolution of Ni occurs by stepwise transformations of fcc=>hcp=>bcc. The prior fcc grain was transformed to the abnormally large hcp ligaments and tiny bcc ligaments. Then, the abnormal hcp ligaments were further dealloyed to smaller bcc ligaments following the P–S OR. This study pave the way for the design of compositionally complex porous materials with a customized morphology and advanced physical properties by dealloying. © 2021 The Authors. ; This work has supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2021R1C1C1007645 ). I.V. Okulov acknowledges support from German Science Foundation under the Leibniz Program (Grant MA 3333/13-1 ).

Liquid metal dealloying (LMD) has recently attracted significant attention. Because the LMD process enables the production of three-dimensional (3D) interconnected non-noble metallic materials. In addition, the metallic melt medium is useful for the development of heterostructure (HS) metal–metal composites. However, the solidified liquid metal phase (low melting point metals such as Mg, Bi, Sn, or Cu) has a much lower strength than the developed ligament phase (e.g., Fe, FeCr, Ti, etc.). In this study, the soft Mg phase was strengthened by adding alloying element of Ni. A eutectic composition of Mg–10 at.% Ni melt leads to the formation of fine eutectic structure of (Mg–Mg2Ni) within 3D interconnected morphology. This hierarchical heterostructured composite consisted of FeCr ligament and Mg–Mg2Ni lamellar, and a high yield strength of 280 MPa and a noticeable elongation (1.5%) were achieved. The complex 3D morphology of ligament and lamellar geometrically constraint each other, and it prevents the early fracture of brittle Mg–Mg2Ni lamellar phase. The alloy design for the LMD melt gives insights for hierarchical HS materials with outstanding mechanical properties for structural applications. © 2021 The Authors. ; This work was supported by JSPS KAKENHI (Grant Number JP20J14001 ). Yeonbeom Jeong acknowledges the support from the GP-MS at Tohoku University . This work has supported by the National Research Foundation of Korea grant funded by the Korea government(MSIT) (No. NRF-2021R1C1C1007645 ). This work was primarily supported by a Grant-in-Aid for Scientific Research on Innovative Areas "Science of New-Class of Materials Based on Elemental Multiplicity and Heterogeneity (Grant No. 18H05452)" from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT, Japan) (H.K and T.W). This work was performed under the ICC-IMR Program of the Institute for Materials Research, Tohoku University.