Microstructural investigations on a series of (Ti70.5Fe29.5)100−xSnx alloys with x=5, 7, and 9 reveal that Sn addition is effective in introducing both structural and spatial heterogeneities in ultrafine eutectic composites stemming from a large temperature difference between two eutectic temperatures upon solidification. The microstructural heterogeneities in these ultrafine eutectic composites strongly enhance the room temperature compressive plasticity up to ∼15.7%.

Systematic investigations on the microstructural evolution of a bimodal eutectic (Ti70.5Fe29.5)91Sn9 ultrafine composite containing Ti3Sn dendrites upon compression reveal that local deformation of the dendrites dominates the early stage of deformation with a plastic strain of εp=5.8%. After further deformation (εp=10.2%), a wavy propagation of shear bands indicative of dissipation of the shear stress is caused by a rotation of the coarse eutectic structure along the interfaces of the bimodal eutectic structure.

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Pressure-induced polymerization (PIP) of metal acetylides is a novel method to synthesize a metal−carbon framework and polycarbide materials with unique structures and properties. However, the pressure required for the PIP of C 2 2− is too high for large-scale synthesis. In this work, we investigated the PIP of monosodium acetylide (NaC 2 H) by performing in situ Raman spectroscopy, infrared spectroscopy, X-ray diffraction, and impedance spectroscopy up to 30 GPa and ex situ gas chromatography−mass spectrometry on the recovered sample. NaC 2 H experiences a phase transition at 7 GPa and polymerizes at 14 GPa, which is the lowest PIP pressure of acetylide to date and already in the working range of a large volume press. At the reaction threshold, the nearest intermolecular C•••C distance is about 2.9 Å, which is almost the same as that of CaC 2 and indicates a topochemical initiation. The PIP is mainly a free radical addition process. The termination of the free radicals limits the composition of the produced polycarbide anions C x H y n− within x − 2 ≤ y + n ≤ x + 2. Our work discloses the threshold of the intermolecular distance for the PIP of acetylide and proposes the reaction mechanism, which furthers the investigation of its high-pressure chemical reaction.