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Post-bond heat treatment (PBHT) is an effective way to improve the bonding quality of a brazed joint. Herein, brazing of a nickel-based single crystal superalloy is carried out using a Ni-Cr-Co-B-Si-Al-Ti-W-Mo filler alloy, and the microstructure and creep property of the brazed joint are systematically investigated using scanning electron microscopy (SEM), Thermo-Calc software, an electron probe micro-analyzer (EPMA), X-ray diffractometer, confocal scanning laser microscope (CSLM), and transmission electron microscopy (TEM). The results reveal that the as-prepared joint only consists of an isothermally solidified zone (ISZ) and an athermally solidified zone (ASZ), where the cubic γ′ phase is observed in the ISZ, and skeleton-like M3B2, γ + γ′ eutectic and reticular G phases are observed in the ASZ. Furthermore, the γ + γ′ eutectic and G phases disappear and the M3B2 alters from a skeleton-like to block-like shape in the ASZ after PBHT. Meanwhile, some lath-like M3B2 phases are precipitated at the edge of the ISZ and several M3B2 phases are precipitated in the base metal, forming a new zone in the brazed joint, namely at the diffusion affected zone (DAZ). Owing to the removal of low melting point eutectics from the as-prepared joint, the creep life also increases from 188 h to 243 h after PBHT. The current work provides a method for the optimization of brazed joints based on the Ni-based single crystal superalloy. [ABSTRACT FROM AUTHOR]

Sn60Pb40 alloy powders were fabricated using the planar flow casting (PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigated. It is observed that the environment of ambient gas in the atomization box has great effects on the morphology of the alloy powders. The microstructures of Sn60Pb40 alloy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated α solid solution and β solid solution. The microstructures of small size powders are extraordinarily undeveloped dendritic eutectic, in which the large majority of the α phase appears nearly spherical, evidently since the cooling rate is higher and the under-cooling is larger. As for the large size powders, since the cooling rate and undercooling are relatively low, lamellar α phase apparently increases in the eutectic microstructures of these powders, and there is even typical lamellar eutectic structure clearly observed in some micro-areas. After remelting tests by DTA, the microstructures of small size powders are transformed, which become composed of large crumby α phase and eutectic (α+β), while those of large size powders change into classical tin-lead structures of primary α phase plus lamellar eutectic (α+β). By studying the microstructures of tin-lead alloy powders, a model has been proposed to predict the microstructure formation of Sn60Pb40 alloy powders. [ABSTRACT FROM AUTHOR]

In this work, the effects of annealing temperatures and time on the microstructure and soft magnetic properties of (Fe 0.83 B 0.11 Si 0.02 P 0.03 C 0.01) 99.5 Cu 0.5 nanocrystalline alloy were investigated using a new rapid annealing process. The results show that at each annealing temperature, there exists an annealing time for optimum soft magnetic properties. The annealing temperature and time were further optimized, and excellent properties with high saturation magnetic induction B s of 1.79 T and low coercivity H c of 2.7 A/m were obtained by annealing at 431 °C for 150 s. A microstructure consisting of uniform and fine α-Fe(Si) grains with high number density and high crystallization volume fraction was found to be the key to ensure high B s and low H c. However, with increasing annealing time, it was found that α-Fe(Si) grains existed aggregation phenomenon (in the form of high-angle grain boundaries), with the simultaneous precipitation of Fe-B compound precipitated in the residual amorphous matrix. This not only causes the uneven distribution of nanocrystals, but also destroys the competitive effect between nanocrystals and the stability of the structure, thus deteriorating the soft magnetic properties. [ABSTRACT FROM AUTHOR]

In this paper, cryogenic treatment (at 77K) was first applied to solve the problem of strength and plasticity balance of body-centered cubic (BCC) type Al 1.4 CrFe 2 Ni 2 high entropy alloy (HEA). The microstructure and mechanical properties of the HEAs after cryogenic treatment was studied systematically. The results show that cryogenic treatment has an intensive effect on the nanophases (B2), dislocations and mechanical properties. The nanophase is refined to 126.05 nm with cryogenic treatment for 24 h, which is 42.7% lower than the matrix alloy. The number of the nanophase is increased by 60%. With the increasing of cryogenic treatment time, the dislocation morphology evolves from short linear shape to long curved shape and ring shape in turn, and the dislocation density increases significantly. Al 1.4 CrFe 2 Ni 2 HEA exhibits excellent mechanical properties (480 HV hardness and 3107 MPa fracture strength) after cryogenic treatment for 24 h, which increase 9.1% and 24.33% than the matrix alloy (440 HV and 2499 MPa) while maintain high fracture strain, up to 40.8%. This is attributed to the volume shrinkage and lattice distortion superposition of HEAs cause the extrusion effect between grains. Under the effect of cryogenic treatment, the internal stress increased with volume shrinkage and the dislocation strengthening obviously. [ABSTRACT FROM AUTHOR]

• The trajectories for optimized B s and H c determined by both annealing temperature and time were established. • A relatively larger B s up to 1.74 T and lower H c of 4.9 A/m were found for the present alloy compared to the nanocrystalline alloys with similar Fe content. • It is found that the precipitated α -Fe (Si) grain number density is the main factor to determine the B s A (Fe 0.83 B 0.11 Si 0.02 P 0.03 C 0.01) 99.5 Cu 0.5 glass former was formulated based on Fe 83 B 11 Si 2 P 3 C 1 alloy and a new rapid annealing method was employed to investigate both the temperature and time effect on the improvement of soft magnetic properties of the amorphous alloy ribbon. The results show that the interval between the first and second crystallization temperature is enlarged by Cu addition. There exists an optimal annealing time corresponding to the optimal B s and H c for the ribbon annealed at each temperature. The maximum B s up to 1.74 T and the minimum H c of 4.9 A/m were obtained for the ribbon annealed at 426 °C for 150 s. The grain number density of precipitated α -Fe(Si) is the main factor in determining the B s. Compared to other nanocrystalline alloys with similar Fe content, the present alloy ribbon annealed by the new method shows a higher B s and a lowest H c , which makes it a promising soft magnetic material used in the field of electrical and electronic industries. [ABSTRACT FROM AUTHOR]

The influences of minor amounts of scandium on the microstructure and mechanical properties of as-cast ZA27 alloy have been experimentally investigated. The experimental results show that as far as the Sc addition is individually concerned, the refinement result of the as-cast ZA27 alloy with 0.5wt.%Sc addition is comparatively better. After alloying with minor amounts of Sc, the coarse dendrites of the ZA27 alloy are refined and transformed into the uniform and small equiaxed grain microstructure; also the eutectics among the grain boundaries become finer. The test results of mechanical properties show that the tensile strength and hardness of the as-cast ZA27 alloy containing 0.5wt.%Sc approach 495 MPa and 120.2 HB, increase by 28.5% and 33.1%, respectively, compared with those of the ZA27 alloy with no addition of Sc element, while the elongation of the alloy is improved to 7.6% from 2.7%. The SEM, EDAX and XRD analyses show that in the ZA27 alloy, the trace element Sc combines with Al to form the square AI3Sc phase particles, which serve as heterogeneous nuclei, facilitating the refinement of the microstructure and the improvement of the mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]