C.B. Xiao
,
Y.F. Had and X.A. Zhang (Cast Superalloys Lab.
,
Beijing Institute of Aeronautical Materials (BIAM)
,
Beijing 100095
,
China)
金属学报(英文版)
The effect of different amounts of silicon on the microstructure of the yttrium modified Ni3Al base alloy IC6 was studied with transmission electron microscope (TEM). The chemical compositions of phases formed due to the presence of silicon and yttrium were analyzed with energy dispersive spectrum(EDS) technique of electron probe microstructural analysis (EPMA). The results showed that a bulk shape phase rich in Mo and Si was formed in the alloys with addition of 0.10-0.20wt%Si and 0.12wt%Y, and that a needle like phase named Y-NiMo was precipitated in the interdendritic area in the alloy with addition of 0.30wt%Si and 0.12wt%Y besides the formation of the bulk shape phase mentioned above. The stress rupture properties under 1100℃/80MPa and the thermal fatigue properties at 1100℃ were improved by adding 0. 12wt%Y but decreased by adding 0.10-0.30wt%Si and 0.12wt%Y. The addition of 0. 10-0.20wt%Si and 0.12wt%Y has no obvious influence on the tensile properties of alloy IC6 at room temperature (R. T.), 760, and 900℃, respectively.
关键词:
silicon
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null
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null
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null
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Journal of Alloys and Compounds
In this work, the influence of element Y on the mechanical properties of the as-cast Mg-5.5Zn-xY-0.8Zr alloys (with element Y content of 0, 1.08, 1.97 and 3.08 wt.%) has been investigated and compared. The results showed that the alloy with Y content of 1.08 wt.% had the superior tensile strength, but its ductility was the lowest. When Y content reached 1.97 or 3.08 wt.%, the tensile strength of the alloys decreased obviously, but the ductility had a little improvement. X-ray phase analysis showed that when Y content was 1.08 wt.%, the alloy mainly contained I-phase and alpha-Mg matrix, whereas when Y content was 1.97 or 3.08 wt.%, besides I-phase and alpha-Mg matrix, W-phase would be formed. And the diffraction peak of W-phase intensified with the increase of element Y content. Based on fracture observations, the influence of I-phase and W-phase on the mechanical properties of the alloys has been explained, respectively. It revealed that I-phase was closely bonded with the Mg matrix and could effectively retard the basal slip, and then strengthened the alloy greatly. However, W-phase was easily cracked during the tensile process, which degraded the mechanical properties. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
As-cast Mg alloys;mechanical properties;I-phase and W-phase;Mg-Zn-Y-Zr alloy;behavior;phase
Transactions of Nonferrous Metals Society of China
The influence of Zr and Y on the cast microstructure of a nickel-based superalloy was investigated by optical microscopy (OM), scanning electron microscopy(SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD). The gamma+gamma' eutectic volume in the superalloy rises notably with the increase of Zr or Y content. Meanwhile, the morphologies of primary MC carbides change from needle and platelet-like to blocky shape with increasing Zr and Y doped. The XRD results show that the primary MC carbide lattice constant increases with Zr and Y additions, and EPMA investigation shows that the platelet-like MC carbides contain primarily Nb and C, while those carbides in blocky shape have 39.2% Zr and 39.6% Nb in average,. These influences on the cast microstructure can be attributed to the atomic size effects of Zr and Y.
关键词:
yttrium;zirconium;carbides;nickel based superalloys;microstructure;solidification;carbide morphology;mechanical-properties;boron;ni3al;yttrium;sulfur
Journal of Materials Research
Starting with a bulk metallic glass-forming alloy Mg61Cu18Ni6Y11, we prepared in situ composites by increasing the Mg content in a series of alloys, Mg-x(Cu0.51Ni0.17Y0.32)(100)-x (65 <= x <= 90), via copper mold casting of rods 4 mm in diameter. The fully glassy alloy at x 65 showed a compressive fracture strength of 755 MPa but no observable macroscopic plasticity prior to failure. Metallic glass-based composites were formed when the Mg content was increased. For x > 80, the glassy phase no longer existed in the as-cast rods. In the composition range of 80 <= x <= 85, needle-shaped Mg solution with a 14H-type long period stacking (LPS) structure appeared as the primary phase in the as-cast microstructure. On further increase of the Mg content up to x = 90, the solidified primary phase became 2H-Mg, coexisting with the remaining eutectic structure. The best combination of mechanical properties was obtained for the alloy at x = 81.5, which showed a fracture strength of 665 MPa and a compressive plastic strain of 11.6%. The specific strength of this alloy was 2.8 x 10(5) N m kg(-1), much higher than conventional cast magnesium alloys. The mechanical properties are discussed in light of the phase selection and microstructural features uncovered in microscopy examinations.
关键词:
bulk metallic-glass;mg-cu-y;period ordered structure;high-strength;mechanical-properties;enhanced plasticity;matrix composite;amorphous-alloys;room-temperature;ductility
Transactions of Nonferrous Metals Society of China
The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr (mass fraction, %) alloy (GW104 alloy) cast by metal mould casting (MMC) and lost foam casting (LFC) were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of alpha-Mg solid solution, eutectic compound of alpha-Mg+Mg(24)(Gd, Y)(5) and cuboid-shaped Mg(5)(Gd, Y) phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 degrees C for 6 h, while the Mg5(Gd, Y) phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.
关键词:
Mg-Gd-Y-Zr alloy;lost foam casting;metal mould casting;microstructure;mechanical property;age-hardening response;tensile properties
