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To investigate the comprehensive effects of the Al and Zr element contents on the microstructure evolution of the AlNbTiVZr series light-weight refractory high entropy alloys (HEAs), five samples were studied. Samples with different compositions were designated Al1.5NbTiVZr, Al1.5NbTiVZr0.5, AlNbTiVZr, AlNbTiVZr0.5, and Al0.5NbTiVZr0.5. The results demonstrated that the actual density of the studied HEA samples ranged from 5.291 to 5.826 g·cm−3. The microstructure of these HEAs contains a solid solution phase with a BCC structure and a Laves phase. The Laves phase was further identified as the ZrAlV intermetallic compound by TEM observations. The microstructure of the AlNbTiVZr series HEAs was affected by both the Al and Zr element contents, whereas the Zr element showed a more dominant effect due to Zr atoms occupying the core position of the ZrAlV Laves phase (C14 structure). Therefore, the as-cast Al0.5NbTiVZr0.5 sample exhibits the best room temperature compression property with a compression strength (σp) of 1783 MPa and an engineering strain of 28.8% due to having the lowest ZrAlV intermetallic compound area fraction (0.7%), as characterized by the EBSD technique. [ABSTRACT FROM AUTHOR]

The interface microzone characteristics determine the thermophysical properties of diamond/Cu composites, while the mechanisms of interface formation and heat transport still need to be revealed. Here, diamond/Cu-B composites with different boron content were prepared by vacuum pressure infiltration. Diamond/Cu-B composites up to 694 W/(mK) were obtained. The interfacial carbides formation process and the enhancement mechanisms of interfacial heat conduction in diamond/Cu-B composites were studied by HRTEM and first-principles calculations. It is demonstrated that boron can diffuse toward the interface region with an energy barrier of 0.87 eV, and these elements are energetically favorable to form the B4C phase. The calculation of the phonon spectrum proves that the B4C phonon spectrum is distributed in the range of the copper and diamond phonon spectrum. The overlapping of phonon spectra and the dentate structure together enhance the interface phononic transport efficiency, thereby improving the interface thermal conductance. [ABSTRACT FROM AUTHOR]