Ductility Improvement of Direct-Cast Gamma TiAl-Based Alloy Sheet

1996 ◽  
Vol 460 ◽  
Author(s):  
Toshihiro Hanamura ◽  
Keizo Hashimoto
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Particle Dispersion ◽  
Alloy Sheet ◽  
High Temperature Strength ◽  
High Oxygen Content ◽  
Room Temperature Ductility ◽  
Average Grain Size ◽  
The Matrix

ABSTRACTFor improving the room temperature tensile ductility of direct-cast gamma TiAl sheets without affecting their high-temperature strength, direct sheet casting with T1B2 particle dispersion is employed and conducted. The T1B2 addition and rapid cooling results in the formation of a fine equiaxed grain microstructure with an average grain size of ∼10μm, contributing to the increase in the room temperature ductility to 2.1% with the high-temperature tensile strength kept at about 200MPa. This improvement of room-temperature ductility is attributable to the following fact. The high oxygen content of this material, about 2500wt. ppm, is not harmful to the tensile ductility when the oxygen is in the solid solution of the 0:2 lamellar phase or in oxide particles, which are fine enough not to cause brittleness to the matrix. From these findings, a principle is proposed that oxygen is not harmful to the ductility of gamma TiAl when its microstructure containing oxygen is fine enough.

Ductility and Strength in Mo Modified TiAl

1990 ◽  
Vol 213 ◽  
Author(s):  
T. Maeda ◽  
M. Okada ◽  
Y. Shida
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Single Phase ◽  
Tensile Ductility ◽  
Rupture Strength ◽  
High Temperature Strength ◽  
Duplex Structure ◽  
Annealed Condition ◽  
Mean Grain Size ◽  
Ternary Additions

ABSTRACTAn investigation has been made on the effect of ternary additions of Mo and other elements on the room temperature tensile ductility and high temperature strength, including creep rupture strength in TiAl based alloys. Mo modified Ti-rich TiAl in an annealed condition exhibited higher tensile ductility at room temperature than other well-known Cr or Mn modified alloys, this resulting from the refinment of mean grain size in the duplex structure of lamellar (γ+α2) and single phase (γ) rather than the crystalline tetragonality of the γ phase. Moreover, creep strength in as cast Ti-rich TiAl is improved with the addition of Mo, and lowered with the addition of Mn. These results suggest that Mo modified Ti-rich TiAl can enhance, the potential of TiAl as a high temperature material more than other ternary modified TiAl.

Influence of Interfacial Characteristics on the Mechanical Properties of Continuous Fiber Reinforced Nial Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
Randy R. Bowman
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Thermal Cycling ◽  
Oxidation Resistance ◽  
Cyclic Oxidation ◽  
Room Temperature ◽  
Matrix Cracking ◽  
High Temperature Strength ◽  
Interfacial Bond ◽  
The Matrix

ABSTRACTAs part of a study to assess NiAl-based composites as potential high-temperature structural materials, the mechanical properties of polycrystalline NiAl reinforced with 30 vol.% continuous single crystal Al2O3 fibers were investigated. Composites were fabricated with either a strong or weak bond between the NiAl matrix and Al2O3 fibers. The effect of interfacial bond strength on bending and tensile properties, thermal cycling response, and cyclic oxidation resistance was examined. Weakly-bonded fibers increased room-temperature toughness of the composite over that of the matrix material but provided no strengthening at high temperatures. With effective load transfer, either by the presence of a strong interfacial bond or by remotely applied clamping loads, Al2O3 fibers increased the high-temperature strength of NiAl but reduced the strain to failure of the composite compared to the monolithic material. Thermal cycling of the weakly-bonded material had no adverse effect on the mechanical properties of the composite. Conversely, because of the thermal expansion mismatch between the matrix and fibers, the presence of a strong interfacial bond generated residual stresses in the composite that lead to matrix cracking. Although undesirable under thermal cycling conditions, a strong interfacial bond was a requirement for achieving good cyclic oxidation resistance in the composite. In addition to the interfacial characterization, compression creep and room temperature fatigue tests were conducted on weakly-bonded NiAl/Al2O3 composites to further evaluate the potential of this system. These results demonstrated that the use of A12O3 fibers was successful in improving both creep and fatigue resistance.

Mechanical Properties and Microstructure of Certain Niaico(Hf) Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
S. M. Russell ◽  
C. C Law ◽  
L. S. Lin ◽  
G. W. Levan
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Martensitic Transformation ◽  
Low Temperatures ◽  
Creep Resistance ◽  
Room Temperature ◽  
Hexagonal Structure ◽  
High Temperature Strength ◽  
Room Temperature Ductility ◽  
Poor Creep Resistance

AbstractCobalt-modified NiAl alloys are being studied for their potential for room temperature ductility and toughness. An alloy of Ni - 29.3 a/o Al - 36.7 a/o Co has shown improved toughness and ductility with respect to binary NiAl alloys due in part to a stress-induced martensitic transformation. Furthermore, the cobalt additions have altered the slip behavior to {110}<111> type from {110} <001> for binary NiAl alloys. Hafnium was added to improve the alloy's relatively poor creep resistance and high temperature strength. Hf was found to be insoluble in the NiAlCo alloy and formed precipitates with a hexagonal structure. The Hfmodified alloy had improved high temperature strength. In addition, the Hf apparently changed the creep mechanism resulting in poorer creep resistance at low temperatures, but improved creep resistance at higher stresses and temperatures.

IMPROVEMENT OF AMBIENT DUCTILITY AND TOUGHNESS BY Γ PHASE PRECIPITATION IN NIAL-CR(MO)/NB ALLOYS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2898-2903 ◽  
Author(s):  
LINZHI TANG ◽  
SHUSUO LI ◽  
SHENGKAI GONG
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Compression Test ◽  
Room Temperature ◽  
High Temperature Strength ◽  
Phase Precipitation ◽  
Room Temperature Ductility ◽  
Type Phase

Effects of different ratios of Ni to Al on the ductility and toughness of Ni 33+ x Al 28- x Cr 30 Mo 4 Nb 5 ( x =0, 6, 9, 12) alloys are investigated. High temperature compression test is also conducted. The results show that with ratio of Ni to Al up to 1.77, γ phase precipitation result in ductility and fracture toughness enhanced at room temperature. The reinforced Cr 2 Nb -type phase and γ phase benefit for the high temperature strength and room temperature ductility, respectively.

Control of interfacial reactions and strength of the SiC/SiC joints brazed with newly-developed Co-based brazing alloy

2007 ◽  
Vol 22 (10) ◽  
pp. 2727-2736 ◽  
Author(s):  
Hua-Ping Xiong ◽  
Wei Mao ◽  
Yong-Hui Xie ◽  
Bo Chen ◽  
Wan-Lin Guo ◽  
...  
Keyword(s):  
High Temperature ◽  
Reaction Layer ◽  
Joint Strength ◽  
Room Temperature ◽  
Temperature Stability ◽  
High Temperature Strength ◽  
Bend Strength ◽  
High Temperature Stability ◽  
The Matrix ◽  
Point Bend

Co-based brazing alloy CoFeNi(Si, B)CrTi was designed for SiC joining. The periodic banded reaction structure that existed at the interface between SiC and the traditional Ni-based or Co-based braze has been eliminated by the new brazing alloy. The maximum room-temperature four-point bend strength of 161 MPa was achieved for SiC/SiC joint under the optimum brazing condition of brazing filler thickness of 120 μm, brazing temperature of 1150 °C, and brazing time of 10 min. The corresponding reaction layer of the SiC/SiC joint is composed of multilayer silicides and TiC band, and many small TiC particles are scattered throughout the matrix of the central part of the joint. The joints thus exhibit stable high-temperature strength. It is believed that the formation of TiC in the joint contributes not only to the elimination of the periodic banded reaction structure, but also to the high joint strength and the high-temperature stability.

Mechanical Properties of Dispersion-Hardened P/M Al-Mn-Cu-Mg-Zn Alloys at Elevated Temperature

2006 ◽  
Vol 519-521 ◽  
pp. 419-424
Author(s):  
Hiroki Adachi ◽  
Kozo Osamura ◽  
Jun Kusui
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Intermetallic Phase ◽  
Peak Level ◽  
Rietveld Analysis ◽  
Intermetallic Phases ◽  
Age Hardening ◽  
High Temperature Strength ◽  
The Matrix ◽  
Zn Alloys

In order to improve the high-temperature strength of an Al-Cu-Mg alloy, Mn was added at supersaturation to form a high-density dispersion of an intermetallic phase. In the P/M Al-3.6Mn- 6.4Cu-3.6Zn-1.7Mg alloy (mass%), rod-like Al-Mn-Cu-Zn quaternary intermetallic phases (Q phase) several hundred nanometers in length were dispersed in the matrix. The chemical composition of the Q phase was determined by TEM/EDX to be 78.8Al-12Mn-8Cu-1.2Zn (at%). The crystal system, space group, and lattice parameters of the unit cell were identified to be orthorhombic, Cmcm and a = 0.76, b = 2.11, c = 1.25 nm, respectively, by Rietveld analysis. Since the matrix of the alloy obtained was of the Al-Cu-Mg-(Zn) system, age-hardening occurred by formation of a GPB zone at room temperature and 448 K. At the peak level of age-hardening at room temperature, the tensile strength at room temperature was 704 MPa, and the elongations were 8.0%. The high temperature strengths at 523 and 573 K were 319 and 141 MPa, respectively, and the elongations were 17 and 34%, respectively.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

ALCHEMI of B2-Ordered Fe50Al45Me5 alloys

1996 ◽  
Vol 54 ◽  
pp. 548-549
Author(s):  
Ian M. Anderson
Keyword(s):  
Room Temperature ◽  
Iron Aluminide ◽  
Low Density ◽  
Intermetallic Alloys ◽  
Practical Applications ◽  
Alloying Additions ◽  
Site Distribution ◽  
Good Corrosion Resistance ◽  
Room Temperature Ductility ◽  
The Matrix

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.

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