Grain boundary directed spinodal decomposition has a substantial effect on the microstructure evolution and properties of polycrystalline alloys. The morphological selection mechanism of spinodal decomposition at grain boundaries is a major challenge to reveal, and remains elusive so far. In this work, the effect of grain boundaries on spinodal decomposition is investigated by using the phase-field model. The simulation results indicate that the spinodal morphology at the grain boundary is anisotropic bicontinuous microstructures different from the isotropic continuous microstructures of spinodal decomposition in the bulk phase. Moreover, at grain boundaries with higher energy, the decomposed phases are alternating α/β layers that are parallel to the grain boundary. On the contrary, alternating α/β layers are perpendicular to the grain boundary.

The purpose of the work is to design a novel impedance adapter to set up a mono-cone standard field generation system with a large clear time and a large dynamic range. To transform the impedance from 50 Ω (the output impedance of the signal generator) to 75 Ω (the input impedance of the cone), the gradient structures with 11 sections are designed for the impedance adapter. The measured VSWR of the system is below 1.5 from 300 to 2.25 GHz. The insertion loss of the designed is about −35 dB. The system with the designed impedance adapter works well. This is validated by the results of the standard open-air test site in National Institute of Metrology, China. K E Y W O R D S75 Ω, impedance adapter, mono-cone, OTAS, time-domain electromagnetic pulse, traceability