The selective corrosion of NiTi alloy was studied using density functional theory calculations, and the dissolution trends of the NiTi-B2 and NiTi-B19’ phases on the initial oxidation stage were compared...

In this paper, the atomic configuration, electronic structure, and work of adhesion for TiN(111)//B2‐NiTi(110) and TiN(111)//B19′‐NiTi(010) interfaces were investigated by first‐principles calculations based on density functional theory (DFT), which aim to provide a theoretical guidance for analyzing the service reliability of TiN films modified NiTi alloy devices. The results of this paper indicated that a hollow‐site stacking structure was formed on the interface when Ti and N were the terminal atoms on two sides. Such interfaces demonstrated a stronger bonding performance and a more stable structure than that with Ni and Ti as the terminal atoms. The work of adhesion of the TiN(111)//B19′‐NiTi(010) interface was 17.47 J/m2, which is greater than the work of fracture of TiN(111) (6.73 J/m2), whereas the work of adhesion of the TiN(111)//B2‐NiTi(110) interface was found to reach 5.49 J/m2, which is lower than the work of fracture of TiN(111). The models of the work of adhesion between the two interfaces indicate that there are significant bond strength changes in the TiN/NiTi interface, when the NiTi substrate undergoes martensitic transformation. The results of this paper contribute significantly to the service reliability analysis of TiN films coated on NiTi alloy devices.

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To investigate the effect of B4C particle size on the microstructure and mechanical properties of B4C/Al composites, and to provide theoretical guidance for the subsequent thermal processing of composites, B4C/Al composites with varying B4C particle sizes (0.2 µm, 0.5 µm, 1 µm, 10 µm) were fabricated using pressureless infiltration. The microstructure of the composites was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the mechanical properties were analyzed by hardness test, three-point bending and high temperature compression. The results indicated that Al3BC and AlB2 were the primary interfacial reaction products in B4C/Al composites, and interface reaction could be alleviated with increasing particle size. B4C/Al composites with larger B4C particle sizes exhibited a relatively uniform and discrete distribution of B4C, while those with smaller B4C particle sizes showed agglomeration of B4C. The Vickers hardness and peak flow stress of B4C/Al composites gradually decreased with the increase of B4C particle size, while the bending strength, flexural modulus, and fracture toughness tended to increase. In addition, when B4C particle size was 10 µm, the composites displayed optimal comprehensive performance with the lowest peak flow stress (150 MPa) and the highest fracture toughness (12.75 MPa·m1/2).

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