Correlations to improve room temperature ductility of refractory complex concentrated alloys

Author(s):  
O.N. Senkov ◽  
D.B. Miracle ◽  
S.I. Rao
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.


Author(s):  
Ian M. Anderson

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.


1989 ◽  
Vol 4 (6) ◽  
pp. 1347-1353 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth ◽  
C. T. Liu

The elastic properties of nickel beryllide have been evaluated from room temperature to 1000 °C. The room temperature modulus is measured to be 186 GPa, which is relatively low by comparison with other B2 aluminides such as NiAl and CoAl. Hardness measurements were carried out on specimens that had compositions over the range from 49 to 54 at. % Be, using both a Vickers microhardness tester and a nanoindentor. It was found that the hardness of NiBe exhibits a minimum at the equiatomic composition. This behavior is similar to that of aluminides of the same crystal structure, e.g., NiAl and CoAl. The effect of interstitial oxygen on the hardness of NiBe has also been studied and the results show that the presence of oxygen in NiBe can cause a significant increase in hardness. It is demonstrated that the hardness increase for the off-stoichiometric compositions is primarily caused by interstitial oxygen and can only be attributed partially to anti-site defects generated in off-stoichiometric compositions. Nickel beryllides appear to have some intrinsic room temperature ductility, as evidenced by the absence of cracking near hardness indentations.


2010 ◽  
Vol 528 (1) ◽  
pp. 355-362 ◽  
Author(s):  
Satoshi Emura ◽  
Kaneaki Tsuzaki ◽  
Koichi Tsuchiya

JOM ◽  
1985 ◽  
Vol 37 (4) ◽  
pp. 36-40 ◽  
Author(s):  
Anthony J. Bryhan

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2757 ◽  
Author(s):  
Ning Cui ◽  
Qianqian Wu ◽  
Zhiyuan Yan ◽  
Haitao Zhou ◽  
Xiaopeng Wang

In this paper, the microstructure, deformability, tensile properties, and phase hardness of the Ti–43Al–2Cr–0.7Mo–0.1Y alloy with a high β phase content were investigated. Microstructural analysis showed that the β phase precipitated not only at the colony boundaries but also inside the lamellae due to its high content. A high-quality forging stock was prepared through one-step noncanned forging. The total deformation reached above 80%, suggesting that the alloy has good hot deformability compared to other TiAl alloys. The deformed microstructure was composed of fine and equiaxed grains due to dynamic recrystallization. The high β phase content was shown to contribute to the decomposition of the initial coarse lamellae. Tensile testing showed that the alloy has good room-temperature ductility, even if the β phase content reaches above 20%. This is inconsistent with a previous study that showed that a large amount of the hard β phase is detrimental to the room-temperature ductility of TiAl alloys. Nanoindentation testing showed that the hardness of the β phase in the current alloy is about 6.3 GPa, which is much lower than that in the Nb-containing TiAl alloys. Low hardness benefits the compatible deformation among various phases, which could be the main reason for the alloy’s good room-temperature ductility. Additionally, the influence of various β stabilizers on the hardness of the β phase was also studied. The β phase containing Nb had the highest hardness, whereas the β phase containing Cr had the lowest hardness.


2010 ◽  
Vol 638-642 ◽  
pp. 1439-1444
Author(s):  
Masuo Hagiwara ◽  
Tomoyuki Kitaura

The grain sizes of two kinds of orthorhombic alloys, namely (O+B2) Ti-22Al-11Nb-2Mo -1Fe and (O+2) Ti-27.5Al-13Nb have been successfully reduced by the addition of trace boron (B) (less than 0.12 wt.%). For example, the grain size in the B2 solution-treated condition was reduced from 1 mm to 80 m by the addition of 0.05% B for both alloys. The tensile elongation of Ti-22Al-11Nb-2Mo-1Fe at room temperature and 650C was increased from 0.3% to 4.3%, and from 8.2% to 30.3%, respectively, by the addition of 0.10% B. Ti-27.5Al-13Nb also showed an improved room temperature ductility by the minor B addition.


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