TOPOGRAPHICAL FEATURE OF HIGH JcYBa2Cu3Ox SUPERCONDUCTOR

1991 ◽  
Vol 05 (12) ◽  
pp. 843-847 ◽  
Author(s):  
A. S. LIU ◽  
H. T. REN ◽  
L. XIAO
Keyword(s):  
Directional Solidification ◽  
Growth Direction ◽  
Random Structure ◽  
Bulk Materials ◽  
Large Plate ◽  
Conduction Plane ◽  
Topographical Feature ◽  
Parallel Growth

Melt-textured growth of polycrystalline YBa 2 Cu 3 O x superconductor using directional solidification created a compact texture consisting of large plate-shaped crystals aligned preferentially parallel to the a – b conduction plane and many ordered parallel growth steps perpendicular to the growth direction of the YBa 2 Cu 3 O x crystal. The new microstructure, which completely substitutes the previous granular and random structure in the sintered bulk materials, exhibits significantly enhanced transport J c values of 23800 A/cm 2 at 77 K and in a H = 2 Tesla field.

Mechanical properties of NiAl-Mo composites produced by specially controlled directional solidification

2012 ◽  
Vol 1516 ◽  
pp. 255-260 ◽  
Author(s):  
G. Zhang ◽  
L. Hu ◽  
W. Hu ◽  
G. Gottstein ◽  
S. Bogner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Directional Solidification ◽  
Creep Resistance ◽  
Room Temperature ◽  
Growth Direction ◽  
Nominal Composition ◽  
Potential Candidate ◽  
In Situ Composites

ABSTRACTMo fiber reinforced NiAl in-situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification (DS) using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. In these composites, single crystalline Mo fibers were precipitated out through eutectic reaction and aligned parallel to the growth direction of the ingot. Mechanical properties, i.e. the creep resistance at high temperatures (HT, between 900 °C and 1200 °C) and the fracture toughness at room temperature (RT) of in-situ NiAl-Mo composites, were characterized by tensile creep (along the growth direction) and flexure (four-point bending, vertical to the growth direction) tests, respectively. In the current study, a steady creep rate of 10-6s-1 at 1100 °C under an initial applied tensile stress of 150MPa was measured. The flexure tests sustained a fracture toughness of 14.5 MPa·m1/2at room temperature. Compared to binary NiAl and other NiAl alloys, these properties showed a remarkably improvement in creep resistance at HT and fracture toughness at RT that makes this composite a potential candidate material for structural application at the temperatures above 1000 °C. The mechanisms responsible for the improvement of the mechanical properties in NiAl-Mo in-situ composites were discussed based on the investigation results.

Resistivity Distribution Characteristics of Metallurgical Silicon Ingot after Directional Solidification

2011 ◽  
Vol 675-677 ◽  
pp. 109-112
Author(s):  
Shu Ang Shi ◽  
Wei Dong ◽  
Shi Hai Sun ◽  
Yi Tan ◽  
Guo Bin Li ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Vertical Section ◽  
Growth Direction ◽  
Silicon Ingot ◽  
Metallurgical Silicon ◽  
High Impurity ◽  
Polarity Transition ◽  
High Impurity Concentration ◽  
Solid Liquid Interface ◽  
Solid Liquid

The distribution of resistivity, impurity and polarity in multicrystalline silicon ingot prepared by directional solidification method was detected. The effect of impurity distribution on resistivity was also researched. The results show that the shapes of equivalence line of resistivity in the cross section and vertical section of the silicon ingot depend on the solid-liquid interface. The resistivity in the vertical section increases with the increasing of solidified height at the beginning of solidification and reaches to maximum at the polarity transition point, then decreases rapidly with the increasing of solidified height and tends to zero on the top of the ingot because of the high impurity concentration. Study proves that the variation of resistivity in the vertical section is mainly relevant to the concentration distribution of the impurities such as Al, B and P in the growth direction.

Grain Competition Mechanism of a Ni3Al-Based Single Crystal Superalloy IC6SX

2013 ◽  
Vol 747-748 ◽  
pp. 797-803 ◽  
Author(s):  
Li Wu Jiang ◽  
Shu Suo Li ◽  
Mei Ling Wu ◽  
Ya Fang Han
Keyword(s):  
Single Crystal ◽  
Directional Solidification ◽  
Processing Parameters ◽  
Growth Direction ◽  
Selection Method ◽  
Single Crystal Superalloy ◽  
Competitive Growth ◽  
Deviation Angle ◽  
Spiral Grain ◽  
Competition Mechanism

The grain competitive growth and elimination during the directional solidification of a Ni3Al-base single crystal superalloy IC6SX prepared by spiral grain selection method was studied systematically. The experimental results revealed that there were 5 kinds of mechanism during the grain competitive growth and elimination. The grains with preferred growth direction and smaller deviation angle to growth direction have stronger competitiveness, and the mutual thwarting of dendrites played an important role in the processing of grains competitive growth. The results can explain the competitive growth mechanism during the directional solidification and can be used to optimize processing parameters to lay an important foundation for improving preparation processes of single crystal superalloys.

Deformation of Diffusion-Bonded Bi-Pst and Directionally Solidified Crystals of TiAl

1996 ◽  
Vol 460 ◽  
Author(s):  
K. Kishida ◽  
D. R. Johnson ◽  
Y. Shimada ◽  
Y. Masuda ◽  
H. Inui ◽  
...  
Keyword(s):  
Directional Solidification ◽  
Diffusion Bonding ◽  
Flow Behavior ◽  
Lamellar Microstructure ◽  
Growth Direction ◽  
Current Status ◽  
Directionally Solidified ◽  
Lamellar Orientation ◽  
Columnar Grain ◽  
And Diffusion

ABSTRACTWith a data base now available on the microstructural characteristics and the deformation, fracture and macroscopic flow behavior of polysynthetically twinned (PST) crystals of γ/α2 TiAl-base alloys, an approach to achieve a good combination of strength, ductility and toughness in γ/α2 TiAl-base alloys was proposed using directional solidification (DS) techniques to produce a columnar grain material with the lamellar orientation aligned parallel to the growth direction. Such alignment of the lamellar microstructure was recently accomplished in γ/α2 TiAl-base alloys of near equiatomic compositions using an appropriately oriented seed crystal from the Ti-Al-Si system.At the same time, bi-PST crystals, each containing a planar boundary parallel to the loading axis were prepared by directional solidification and diffusion bonding of two PST crystals. Such bi-PST crystals were deformed in tension at room temperature and their deformation behavior was examined in terms of the compatibility requirements imposed at the grain boundary and the interaction of the two component PST crystals.In this paper, (i) the current status of our DS processing efforts, (ii) some results of microscopic characterization of grain boundaries in diffusion bonded bi-PST crystals and (iii) results of deformation experiments of bi-PST crystals prepared by DS processing and diffusion bonding, will be reported.

Tilted Dendritic Growth Dynamics and Dendrite to Degenerate Seaweed Transition in Directional Solidification: Insights from Phase-Field Simulations

2018 ◽  
Vol 15 ◽  
pp. 128-153
Author(s):  
Hui Xing ◽  
Xiang Lei Dong ◽  
Jian Yuan Wang ◽  
Ke Xin Jin
Keyword(s):  
Directional Solidification ◽  
Misorientation Angle ◽  
Phase Field ◽  
Dendritic Growth ◽  
Growth Dynamics ◽  
Growth Direction ◽  
Primary Spacing ◽  
Stability Range ◽  
Spacing Selection ◽  
Pulling Velocity

In this paper, we review our results from phase field simulations of tilted dendritic growth dynamics and dendrite to seaweed transition in directional solidification of a dilute alloy. We focus on growth direction selection, stability range and primary spacing selection, and degenerate seaweed-to-tilted dendrite transition in directional solidification of non-axially orientated crystals. For growth direction selection, the DGP law (Phys. Rev. E, 78 (2008) 011605) was modified through take the anisotropic strength and pulling velocity into account. We confirm that the DGP law is only validated in lower pulling velocity. For the stability range and primary spacing selection, we found that the lower limit of primary spacing is irrelative to the misorientation angle but the upper limit is nonlinear with respect to the misorientation angle. Moreover, predicted results confirm that the power law relationship with the orientation correction by Gandin et al. (Metall. Mater. Trans. A. 27A (1996) 2727-2739) should be a universal scaling law for primary spacing selection. For the seaweed-to-dendrite transition, we found that the tip-splitting instability in degenerate seaweed growth dynamics is related to the M-S instability dynamics, and this transition originates from the compromise in competition between two dominant mechanisms, i.e., the macroscopic thermal field and the microscopic interfacial energy anisotropy.

Multi-phase field simulation of competitive grain growth for directional solidification

2021 ◽  
Author(s):  
Chang-sheng Zhu ◽  
Zi-hao Gao ◽  
Peng Lei ◽  
Li Feng ◽  
Bo-rui Zhao
Keyword(s):  
Heat Flow ◽  
Grain Boundary ◽  
Directional Solidification ◽  
Phase Field ◽  
Flow Direction ◽  
Orientation Angle ◽  
Growth Direction ◽  
Model Alloy ◽  
Competitive Growth ◽  
Multi Phase

Abstract The multi-phase field model of grain competitive growth during directional solidification of alloy was established, solving multi-phase field models for thin interface layer thickness conditions, grain boundary evolution and grain elimination during the competitive growth of SCN-0.24wt% camphor model alloy bi-crystals were investigated, the effects of different crystal orientations and pulling velocities on grain boundary microstructure evolution were quantitatively analyzed. The results show that in the competitive growth of convergent bi-crystals, when favorably oriented dendrites are in the same direction as the heat flow and the pulling speed is too large, the orientation angle of the bi-crystal from small to large is the normal elimination phenomenon of the favorably oriented dendrite blocking the unfavorably oriented dendrite, and the grain boundary is along the growth direction of the favorably oriented dendrite, and when the pulling speed becomes small, the grain boundary shows the anomalous elimination phenomenon of the unfavorably oriented dendrite eliminating the favorably oriented dendrite. In the process of competitive growth of divergent bi-crystal, when the growth direction of favorably oriented dendrites is the same as the heat flow direction and the orientation angle of unfavorably oriented grains is small, the frequency of new spindles of favorably oriented grains is significantly higher than that of unfavorably oriented grains, and as the orientation angle of unfavorably oriented dendrites becomes larger, the unfavorably oriented grains are more likely to have stable secondary dendritic arms, which in turn develop new primary dendritic arms to occupy the liquid phase grain boundary space, but the grain boundary direction is still parallel to favorably oriented dendrites. In addition, the tertiary dendritic arms on the developed secondary dendritic arms may also be blocked by the surrounding lateral branches from further developing into nascent main axes, this blocking of the tertiary dendritic arms has a random nature, which can have an impact on the generation of nascent primary main axes in the grain boundaries.

Alignment of the lamellar orientation of multi-component TiAl alloys by directional solidification (DS) and mechanical properties of DS ingots

2002 ◽  
Vol 753 ◽  
Author(s):  
Y. Omiya ◽  
S. Muto ◽  
T. Yamanaka ◽  
D. R. Johnson ◽  
H. Inui ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Directional Solidification ◽  
Lamellar Structure ◽  
Growth Direction ◽  
Alloying Elements ◽  
Tial Alloys ◽  
Creep Properties ◽  
Lamellar Orientation ◽  
Loading Axis ◽  
Better Than

ABSTRACTBy using an appropriately oriented seed from the TiAl-Si system (Ti-43Al-3Si), the TiAl/Ti3Al lamellar structure has been successfully aligned parallel to the growth direction for TiAl ingots of the Ti-Al-Nb, Ti-Al-Nb-Si, Ti-Al-Ta-Si systems on the basis of the recently proposed method to predict the appropriate compositions. The Al equivalents for Nb and Ta are reevaluated in order to extend the proposed method to large addition (above a several at. %) of these alloying elements. These DS ingots with the lamellar structure all aligned parallel to the loading axis exhibit creep properties far better than conventionally produced TiAl ingots so far reported.

Synthesis of Unidirectionally Solidified Y‐Ba‐Cu‐0 Bulk Superconductors with High Critical Current Densities

1989 ◽  
Vol 169 ◽  
Author(s):  
E. Yanagisawa ◽  
S. Kondoh ◽  
J. Shimoyama ◽  
J. Kase ◽  
T. Matsubara ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Current ◽  
Applied Magnetic Field ◽  
Bulk Materials ◽  
Large Plate ◽  
Bulk Superconductors ◽  
Plate Shape ◽  
Current Densities ◽  
Melt Solidification

Abstract(Y,Ho)‐Ba‐Cu‐0 superconductors with the high critical current densities (Jc) in an applied magnetic field have been synthesized by a unidirectional melt solidification method. Melt solidified bulk materials are composed of large plate‐shape (Y,Ho)Ba2Cu3Oy crystals which contain small (∼5 um) particles of (Y.Ho)2BaCuO5. The Jc value of the melt solidified (Y,Ho)‐Ba‐Cu‐0 sample is ∼10000 A/cm2 at 77K, H = IT and this value is much higher than the value of 4200 A/cm2 of the melt solidified Y‐Ba‐Cu‐O sample.

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