In this study, tapered slots with an opening width about 200 μm were artificially fabricated in IN738LC superalloy to imitate service cracks. The 'cracks' were repaired by diffusion brazing with a Ni-Cr-Co-Al-Ta-B filler alloy at 1150°C and then heat treated at 1180°C (HT-A) and 1190°C (HT-B), respectively. A joint with uniform microstructure, chemical composition and hardness was obtained using HT-B. The mechanisms of the borides evolution during homogenisation were discussed. The tensile strength of the HT-B joint tested at 20, 600 and 800°C reached up to approximately 96, 90 and 87% of the base metal, respectively. The fracture modes of the joints tensile tested at various temperatures were discussed.

A three-dimensional aggregate generation and packing algorithm applicable for modeling asphalt mixture with high content of graded aggregates is presented in this paper. In the algorithm, arbitrary-shaped polyhedra are used to model aggregates, so that the effect of aggregate shape on the mechanical performance of asphalt mixture can be considered. The algorithm consists of two steps: Aggregate generation and packing. Polyhedra are created by extending triangular fundaments and treated as visualized aggregates after passing through convex control and sharpness judgment. After that, graded aggregates are taken out from the aggregate base and randomly packed in a given cylindrical or cubical region one by one equiprobably. Overlapping between nearby aggregates is avoided by the help of Boolean partition operation in ANSYS. Finally, some asphalt mixture samples with a given gradation are modeled as examples, and their effective elastic properties and creep behaviors under uniaxial compression are simulated.

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Slots with uneven width were cut by femtosecond laser in small plates of IN738LC superalloy to imitate service cracks. The 'cracks' were repaired by diffusion brazing using BNi-1a or a mixed filler alloy at 1100°C. The joint region was composed of isothermal solidification zone (ISZ), diffusion affected zone (DAZ) and precipitate zone (PZ). The compositions were different between the upper and lower ISZ due to the variation of gap width. The sample, repaired with two kinds of filler metals, had similar DAZ microstructure. PZ of mixed filler alloy bonded sample had a similar microstructure with that of BNi-1a, but less borides. The maximum gap sizes of complete isothermal solidification were almost the same for different filler alloys, followed a square root relationship with time. However, PZ of BNi-1a bonded was larger, resulting from a more base metal dissolution. The relationship between the PZ, ISZ and crack width is discussed.

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