Jinlai Liu

Intergrowth of P phase with mu phase in a Ru-containing single-crystal Ni-based superalloy

The precipitation of topologically close-packed (TCP) phases in a Ru-containing single-crystal Ni-based superalloy has been investigated. The high-angle annular dark field, selected area electron diffraction, and high-resolution transmission electron microscopy were used to analyze the TCP precipitates in this study. The intergrowth of P phase with µ phase was found. This finding indicates that P phase may nucleate at stacking faults and subsequently grow at the expense of µ phase. The orientation relationship between P and µ phases was and .

Influence of temperature on tensile behavior and deformation mechanism of Re-containing single crystal superalloy

Abstract Tensile properties of a Re-containing single crystal superalloy were determined within the temperature range from 20 to 1 100 °C with a constant strain rate of 1.67×10−4 s−1. From room temperature to 600 °C, the yield strength increases slightly with increasing temperature. The yield strength decreases to a minimum at 760 °C, while a maximum is reached dramatically at 800 °C. The elongation and area reduction decrease gradually from room temperature to 800 °C. Above 800 °C, the yield strength decreases significantly with increasing temperature. The γ′ phase is sheared by antiphase boundary (APB) below 600 °C, while elongated SSF (superlattice stacking fault) is left in γ′ as debris. At 760 °C the γ′ phase is sheared by a/3〈112〉 superpartial dislocation, which causes decrease of yield strength due to low energy of SSF. Above 800 °C, dislocations overcome γ′ through by-passing mechanism.

Plastic deformation inhomogeneity in a single crystal nickel-base superalloy

Extension and compression tests at different temperatures with various strain rates have been carried out on DD8 single crystal superalloys with [0 0 1] [1 1 0] and [1 1 1] orientations. The results show that plastic deformation heterogeneity (P-L effect) occurs in the temperature range from 300 to 700 degreesC at the strain rate of 3.3 x 10(-4) S-1 and also in the strain rate range of 1.3 x 10(-4)-5.3 x 10(-4) S-1 at 700 degreesC for the [0 0 1]-oriented single crystal nickel-base superalloy during extension. The dependence of the plastic deformation inhomogeneity on the crystallographic orientations during compression under the strain rate of 1.0 x 10(-4) S-1 at 550 degreesC were investigated, and the results indicate that the tendency to the plastic deformation inhomogeneity decreases in the order of [0 1 1], [0 0 1] and [1 1 1]. The mechanical tests display that this plastic instability may lead to the catastrophic drop in yield strength of the alloys, but can be removed by a new heat treatment, with which the yield strength can be improved

Effect of ruthenium on γ′ precipitation behavior and evolution in single crystal superalloys

Abstract The effect of Ru on γ′ precipitation behavior and evolution in single crystal superalloys with different Ru contents were investigated by scanning electron microscopy with energy dispersive spectroscopy, 3D atomic probing, differential scanning calorimetry. The results show that the solvus of the γ′ phase decreases gradually with increasing Ru content in the alloys by casting or by the same solution and aging treatments, the alloy with a larger Ru content yields a smaller γ′ phase. The addition of Ru increases the growth rate and coarsening rate of the γ′ phase. Ru mainly distributes in the γ phase, which causes more Re and Mo partition into the γ′ phase, increasing the absolute value of mismatch and the rafting rate of the γ′ phase.

Variation of microstructure by Ru additions in a single crystal Ni based superalloy

Abstract The microstructural variation of three single crystal Ni based superalloys with various Ru contents has been investigated. The as cast, solid solution and fully heat treated microstructures were quantitatively analysed. The size of γ′ phase was decreased both in dendrite core and interdendritic regions with Ru additions after a solid solution heat treatment. Appropriate heat treatment schemes of three alloys were determined in terms of quantitative and qualitative microstructural characterisation. It was found that the size and volume fraction of γ′ phase were decreased, and the width of γ matrix channels was reduced in the dendrite core regions of fully heat treated microstructure with the additions of Ru. Moreover, the well known reverse partitioning occurred with increasing Ru content. The γ/γ′ lattice misfits changed from positive to negative and became more negative with Ru additions. The variation of γ/γ′ lattice misfit was caused by the changes of partitioning ratios of alloying elements via Ru additions.

Precipitation of ß-NiAl/Laves eutectics in a Ru-containing single crystal Ni-Based superalloy

The precipitation of B2 ß-NiAl/C14-Laves eutectics with a volume fraction of ∼0.5% in the interdendritic γ/γ′ eutectic regions of a 3 wt% Ru-containing single crystal Ni-based superalloy has been characterized. It is found that the eutectic reaction Liquid→ß+Laves (C14) takes place at the end of solidification process. Transmission electron microscopy image shows that numerous fine “butterfly-like” Laves precipitates with a size of ∼30 nm are embedded in the coarse blocky ß-NiAl, suggesting a coherent or semi-coherent interface between these two phases. The crystallography relationship of

Effect of Ru on microstructural evolution during heat treatment in single crystal superalloys

(0001)_{Laves} //(\bar 110)_\beta

Effect of ruthenium on tensile properties of a single crystal Ni-based superalloy

and

Role of Re and Co on microstructures and γ′ coarsening in single crystal superalloys

[11\bar 20]_{Laves} //[111]_\beta

Effect of Ru additions on very high temperature creep properties of a single crystal Ni-based superalloy

between Laves and ß-NiAl phase was obtained in terms of selected area electron diffraction patterns. Electron probe microanalysis results reveal that 3 wt% Ru addition makes more Al, Ta and other refractory elements segregate to the interdendritic regions, which is believed to be the main reason for this undesirable eutectic reaction. In addition, the formation of these eutectics is found to be strongly affected by solidification conditions.