Y. P. Zhang
,
J.X. Zhu
,
Y. Q. Wang and J.Y.Su(Institute of Cast Iron Research
,
Xi'an University of Technology
,
Xi'an 710048
,
China)(Department of Mechanical Engineering
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China)
金属学报(英文版)
This paper deals with an important role of silicon in producing ductile iron with quenched complex structure of bainite and martensite. The samples are cast in permanent mold and quenched in solution of sodium silicate. The result of thc experiments shows that the austenizing temperature should rise with increasing silicon content, otherwise much undissolved ferrite is present in the matrix after quenching. However the undissolvec ferrite can be decreased greatly or even eliminated by adding appropriate amount of ooron. On this condition, the amount of bainite gets increasing and the amount of residual austenite decreasing with the silicon cortent increasing. An approach has also been made to the mechanism of the effect of silicon on the transformation of bainite in ductile iron. The T.T.T. curves measured show that the increase of sllicon content causes the curve to shift to the left. This is quite different from the fact in steel.
关键词:
ductile iron
,
null
,
null
,
null
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 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 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
Qijie ZHAI
,
Li FU
,
Huaying ZHAI
材料科学技术（英文）
Effect of Nb on microstructure and mechanical properties of chilled cast iron at room and elevated temperatures is studied in this research. The results demonstrate that the cast structure and mechanical properties of chilled cast iron at room and elevated temperatures are improved with the addition of trace amount of Nb. However, if Nb was added too much, the cast structure and mechanical properties of chilled cast iron would deteriorate. The suitable content of Nb in chilled cast iron is about 0.05% (mass fraction). Except the dissolution in the matrix of cast iron the excessive Nb will form Nb-rich phases in three morphologies. Those are lumpy NbC, complicated strip-like phase and compound with pearlite structure.
关键词:
Nb
,
null
,
null
,
null
Journal of Alloys and Compounds
This work mainly investigated the mechanical properties of as-cast Mg-Zn-Y-Zr Mg alloys with Zn/Y ratio about 0.97. Tensile results show that when Zn/Y ratio is constant, the alloy (with Zn and Y contents of 3.93 and 4.14 wt.%, respectively) has the highest strength. XRD analysis shows that the alloys are mainly composed of alpha-Mg matrix and W-phase. With the contents of Zn and Y increasing, the diffraction peaks of W-phase are gradually intensified. In addition, microstructure observation indicates that with the increase of Zn and Y contents, the grain boundaries are gradually coarsened by W-phase. Based on the microstructure observation and fracture analysis, the change of the mechanical properties has been explained. (C) 2007 Elsevier B.V. All rights reserved.
关键词:
Mg-Zn-Y-Zr alloys;the mechanical properties;W-phase;icosahedral phase;microstructure;behavior
M. Mostafavi
钢铁研究学报(英文版)
The effects of 2.2% Ni and 0.6% Mo additions on the kinetics, microstructure and mechanical properties of ductile aluminum cast iron were studied in the as-cast and tempered conditions. Test bars machined from cast to size samples, were used for mechanical and metallurgical studies. The results showed that the addition of Ni and Mo to the base iron produces an upper bainitic structure resulting in an increase in strength and hardness. The same trend was shown when the test bars tempered from 300oC in the range of 300 to 400oC. The elongation increased with increasing the temperature from 300 to 400oC. The carbon content of the retained austenite also increased with increasing temperature. The results also showed that the kinetics, microstructure and mechanical properties of this iron are similar to Ni-Mo alloyed silicon ductile iron.
关键词:
Ductile aluminum cast iron;Acicular bainite
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
Journal of Materials Science
The microstructure and mechanical properties of a Mg-1.48Gd-1.13Y-0.16Zr (at.%) alloy in the as-cast, solution-treated, peak-aged and over-aged conditions have been investigated by a combination of thermodynamic calculations and experimental approaches. It is shown that both the Mg(24)(Gd,Y)(5) and cuboid-shaped Mg(5)(Gd,Y) phases exist in the as-cast sample, which is in good agreement with the Scheil solidification model. The former is dissolved during solution treatment, while the latter persists and coarsens. Subsequent artificial ageing results in the formation of metastable beta' precipitates within the alpha-Mg matrix and along the grain boundaries. The peak-aged alloy exhibits maximum ultimate tensile strength and tensile yield strength of 370 and 277 MPa, respectively, at room temperature. Moreover, the strengths decrease gently from room temperature to 250 A degrees C with a gradual increase of elongation. The strengthening contributions to the yield strength are quantitatively evaluated from individual strengthening mechanisms by using measured microstructural parameters. The modelled yield strengths are compared with the experimental results and a reasonable agreement is reached.
关键词:
y-zr alloys;mg-y;wt.percent alloy;precipitation;250-degrees-c;behavior;system;al
