THE INVESTIGATION ON LAMELLAR MICROSTRUCTURE TRANSFORMATION AND STABILITY IN TIAL BASED INTERMATELLICS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2279-2284
Author(s):  
WEI ZHANG ◽  
YUE MA ◽  
SHENGKAI GONG
Keyword(s):  
Lamellar Structure ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Microstructure Transformation ◽  
Β Phase ◽  
Microstructure Stability ◽  
The Stability ◽  
Fully Lamellar

Microstructure stability in fully lamellar (FL) structure TiAl based intermatellics have been studied. The experiment results have shown that the smaller the lamellar spacing is, the more instable the lamellar structure is. The distinct lamellar spheroidization occurs at 1150°C holding for 24h. This phenomena may be caused by lamellar coarsening and decomposition. The linear residual β phase distributed in the Ti -47 A 1-2 Cr -2 Nb alloy may prevent lamellar spheroidization and improves the stability of lamellar structure significantly.

Effect of B Addition on Thermal Stability of Lamellar Structure in Ti-47Al-2Cr-2Nb Alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Y. Yamamoto ◽  
N. D. Evans ◽  
P. J. Maziasz ◽  
C. T. Liu
Keyword(s):  
Thermal Stability ◽  
Lamellar Structure ◽  
Lamellar Microstructure ◽  
Dominant Mode ◽  
Microstructural Change ◽  
Β Phase ◽  
B Additions ◽  
Discontinuous Coarsening ◽  
Fully Lamellar ◽  
Thermal Stability Of

ABSTRACTThermal stability of fully lamellar microstructures in Ti-47Al-2Cr-2Nb (at.%) alloys with and without B additions has been evaluated in the temperature range of 800 to 1200°C. The alloy with 0.15B exhibits an α2 + γ fully lamellar microstructure containing ribbon-like structures (TiB2+β) inside the lamellar colonies. During aging at 800 and 1000°C, β particles surrounded by γ grains form adjacent to the ribbon-like structures. The formation of these grains is attributed to the precipitation of thin plate-like β phase along {1100} within the TiB2 ribbon particles, resulting in the loss of α2 plates around the ribbon-like structure by scavenging Ti. This allows coarsening γ lamellar plates to form new γ grains, and then the ribbon-like structure completely dissolves to leave only β particles. At 1200°C, discontinuous coarsening (DC) of the lamellae becomes the dominant mode of microstructural change for all the alloys. However, the ribbon-like structures in the alloy with B additions play a role in pinning the DC cells, which leads to higher thermal stability of the lamellar microstructure in that alloy.

C11b/C40 Lamellar Structure in a Ta-added Molybdenum Disilicide

2000 ◽  
Vol 646 ◽  
Author(s):  
Fu-Gao Wei ◽  
Yoshisato Kimura ◽  
Yoshinao Mishima
Keyword(s):  
Mechanical Properties ◽  
Orientation Relationship ◽  
Binary Alloy ◽  
Lamellar Structure ◽  
Molybdenum Disilicide ◽  
Lamellar Microstructure ◽  
Polycrystalline Alloys ◽  
Lamellar Interface ◽  
Fully Lamellar ◽  
Microstructural Control

ABSTRACTC11b/C40 fully lamellar microstructures, similar to the well-known TiAl/Ti3Al lamellae, were obtained in Ta- and Nb-added MoSi2 polycrystalline alloys in a previous work. In the present study, the crystallography of the lamellar structure is investigated in a MoSi2-15mol%TaSi2 pseudo-binary alloy after homogenized at 1400°C for 168h, in order to provide some useful parameters for microstructural control to improve mechanical properties. The orientation relationship between C11b and C40 phases and its three distinct variants were identified. Coherency of the lamellar interface is analyzed in comparison with the TiAl/Ti3Al lamellae. Approach to modify the C11b/C40 lamellar microstructure to increase its coherency is discussed based on the results obtained.

scholarly journals Stability of a Lamellar Structure – Effect of the True Interlamellar Spacing on the Durability of a Pearlite Colony / Stabilność Struktury Płytkowej – Wpływ Rzeczywistej Odległości Międzypłytkowej Na Trwałość Kolonii Perlitu

2015 ◽  
Vol 60 (4) ◽  
pp. 2499-2504 ◽  
Author(s):  
A. Czarski ◽  
T. Skowronek ◽  
P. Matusiewicz
Keyword(s):  
Lamellar Structure ◽  
Structural Unit ◽  
Lamellar Microstructure ◽  
Interlamellar Spacing ◽  
Metal Alloys ◽  
Lamellar Morphology ◽  
The Subject ◽  
Pearlite Colony ◽  
The Stability ◽  
Lamellar Pearlite

A lamellar microstructure is, beside a granular and dispersive one, the most frequently observed microstructure in the case of metal alloys. The most well-known lamellar microstructure is pearlite, a product of a eutectoidal transformation in the Fe-Fe3C system. The lamellar morphology of pearlite - cementite and ferrite lamellae placed interchangeably within one structural unit described as a colony - is dominant. The durability of the lamellar morphology is much diversified: in the microstructure of spheroidizingly annealed samples, one can observe areas in which the cementite is thoroughly spheroidized, next to very well-preserved cementite lamellae or even whole colonies of lamellar pearlite. The mentioned situation is observed even after long annealing times. The causes of such behaviour can vary. The subject of the previous work of the authors was the effect of the orientation between the ferrite and the cementite on the stability of the lamellar morphology. This work constitutes a continuation of the mentioned paper and it concerns the effect of the true interlamellar spacing on the stability of the lamellar morphology of cementite.

The Study on TiAl Based Alloy Blade Casting Structure by Bottom Pouring Vacuum Casting

2012 ◽  
Vol 503-504 ◽  
pp. 400-403
Author(s):  
Xi Cong Ye ◽  
Wei Guang Zhao ◽  
Wen Jun Liu ◽  
Shuang Qing Tang ◽  
Zi Fan Fang
Keyword(s):  
Lamellar Structure ◽  
Lamellar Spacing ◽  
Alloy Structure ◽  
Vacuum Suction ◽  
Vacuum Casting ◽  
Grain Sizes ◽  
Bottom Position ◽  
Blade Casting ◽  
Bottom To Top ◽  
Fully Lamellar

In this paper, the bottom pouring vacuum suction casting is used, and the TiAl-based alloy blade with a certain flexivity, the brim thickness 1.5mm, and the blade Falcon with high 8mm, width 10mm, length 27mm was obtained. The structures of this blade are studied. The grain sizes are different from bottom to top, in bottom position, the blade leaves structure have the equiaxed, and the central part have the columnar crystals. The TiAl-based alloy structures have fully lamellar. Comparing with different position structures, the bottom position TiAl based alloy structure have the least lamellar space, is about 0.13μm; the average space of top lamellar structure is about 0.38μm; the central region of the lamellar spacing slightly larger than the bottom area.

The Yield Stress of the Fully-Lamellar Microstructure

1996 ◽  
Vol 460 ◽  
Author(s):  
Y. Q. Sun
Keyword(s):  
Grain Size ◽  
Yield Stress ◽  
Multilayer Structure ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Lamellar Thickness ◽  
Polycrystalline Microstructure ◽  
Fully Lamellar ◽  
The Relationship ◽  
Lamellar Interfaces

ABSTRACTThis paper is an inquiry into the relationship between the yield stress and the two length parameters in the fully-lamellar polycrystalline microstructure, the grain-size dCB and the lamellar thickness dLM. Deformation in the multilayer structure is assumed to proceed by dislocations propagating in the formation of a succession of mutually interacting pileups, blocked at the lamellar interfaces and piled-up ultimately against the grain boundary. An important case suggested is a yield stress independent of the grain size, sensitive only to the lamellar spacing.

On the Effects of Interstitial Elements on Microstructure and Properties of Ternary and Quaternary TiAl based alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Jean-Pierre Chevalier ◽  
Mélanie Lamirand ◽  
Jean-Louis Bonnentien
Keyword(s):  
Yield Stress ◽  
Fracture Strain ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Quaternary Alloys ◽  
Ultra High Purity ◽  
C And N ◽  
Fully Lamellar ◽  
Kinetics Of ◽  
Interstitial Elements

ABSTRACTTi-Al-Cr ternary and Ti-Al-Cr-Nb quaternary alloys have been studied as a function of initial purity and added interstitial content. Using strict clean processing together with either ultra high purity or commercial purity alloys, the effects of interstitial elements (essentially O, but also C and N) on microstructure and hardness, yield stress and fracture strain have been studied for both fully lamellar microstructures and duplex microstructures. The results are clear and similar trends are observed : as long as they do not precipitate, these stabilise the lamellar microstructure and affect the kinetics of the α-γ phase tranformation, leading to a higher than equilibrium value for the α2 phase for continuous cooling. Both the lamellar spacing and the α2 phase fraction correlate with increased hardness and yield stress, and also with decreasing fracture strain. The effects are significant.

scholarly journals Control of the Lamellar Structure and Analysis of Tensile Properties of TiC/Ti-6Al-3Sn-9Zr-1.5Mo Composite Produced by In Situ Casting Technique

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 160
Author(s):  
Dongdong Zhu ◽  
Duo Dong ◽  
Li Liu ◽  
Xiaohong Wang ◽  
Jiqiu Qi
Keyword(s):  
Heat Treatment ◽  
Ambient Temperature ◽  
Tensile Properties ◽  
Lamellar Structure ◽  
Tensile Elongation ◽  
Lamellar Microstructure ◽  
Casting Technique ◽  
Heat Treated ◽  
Fully Lamellar

In the present paper, new heat treatment was performed on 10 vol.% TiC/Ti-6Al-3Sn-9Zr-1.5Mo composite fabricated by an in situ casting technique. The aim is to obtain fully lamellar structure in matrix, control the lamellar structure quantitatively and understand the variation of the tensile properties of as-cast and heat-treated composites. For as-cast composite, matrix exhibited fully lamellar structure with some extent of basket-weave characteristics, and reinforcement was mainly in fine rod and strip shape. After β heat treatment, matrix microstructure was refined visibly. As the new cooling method was employed, wider α lath in matrix was obtained. The composite with very fine lamellar structure showed better yield strength (YS) in comparison with that with coarse lamellar microstructure below 650 °C. At 700 °C, fine grain strengthening cannot exert effective influence on tensile strength. It is proved that the enhanced YS is mainly ascribed to the refinement of α lath at ambient temperature. The heat-treated composites with wider α lath displayed excellent ductility at ambient temperature. Above 600 °C, the effect of α phase size on tensile elongation was negligible in the heat-treated composites, since matrix was softened.

Microstructural Effect on Environmental Embrittlement of Isothermally Forged TiAl-Based Intermetallic Alloys

2002 ◽  
Vol 753 ◽  
Author(s):  
T. Takasugi ◽  
T. Tsuyumu ◽  
Y. Kaneno ◽  
H. Inoue
Keyword(s):  
Tensile Strength ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Testing Temperature ◽  
Intermetallic Alloy ◽  
Dual Phase ◽  
Intermetallic Alloys ◽  
Environmental Embrittlement ◽  
Fully Lamellar ◽  
Microstructural Effect

ABSTRACTThe TiAl-based (Ti-46Al-7Nb-1.5Cr (at%)) intermetallic alloy was tensile tested in vacuum and air as a function of temperature to investigate microstructural effect on the moisture-induced embrittlement. The reduction in tensile strength (or elongation) due to testing in air diminishes as testing temperature increases. From the fracture strength (or elongation)-temperature curves, it was found that the near gamma grain microstructure was most resistant, and the dual-phase microstructure most susceptible to moisture-induced embrittlement. Also, the moisture-induced embrittlement of the TiAl-based intermetallic alloy with fully lamellar microstructure depends on the lamellar spacing, and reduced with decreasing lamellar spacing.

Interfacial strengthening of β phase in a fully lamellar structure of TiAl alloy containing W

2005 ◽  
Vol 85 (7) ◽  
pp. 377-385 ◽  
Author(s):  
H. Zhu * ◽  
D. Y. Seo ◽  
K. Maruyama ◽  
P. Au
Keyword(s):  
Lamellar Structure ◽  
Tial Alloy ◽  
Β Phase ◽  
Fully Lamellar
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