CONTROLLING EMBRITTLEMENT AT GRAIN BOUNDARIES IN INTERMETALLIC COMPOUNDS

1988 ◽  
Vol 49 (C5) ◽  
pp. C5-811-C5-821 ◽  
Author(s):  
T. TAKASUGI
Keyword(s):  
Grain Boundaries ◽  
Intermetallic Compounds

Effects of Ca and RE Additions on the Precipitation and Microstructure of As-Cast AZ91 Alloy

2017 ◽  
Vol 865 ◽  
pp. 30-35 ◽  
Author(s):  
Li Fu ◽  
Qi Chi Le ◽  
Pei Li Gou ◽  
Xi Bo Wang ◽  
Xuan Liu
Keyword(s):  
Intermetallic Compound ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Lamellar Structure ◽  
Az91 Alloy ◽  
Sem Images ◽  
Xrd Pattern ◽  
Microstructure Changes ◽  
Polygonal Structure ◽  
Cast Alloys

The effect of Ca and RE metal additions on the precipitation and microstructure of as-cast AZ91 alloy was systematically investigated. It was found that Ca and RE additions could result in phase and microstructure changes. The XRD pattern showed the crystallite phase of as-cast AZ91 alloys consists of α-Mg matrix and β-Mg17Al12, however, after adding 1.5wt. % Ca and 0.8wt. % RE (0.5wt. % Sm and 0.3wt. % La), peaks coincident with Al2Ca, Al2Sm and Al11La3 intermetallic compounds were found, suggesting the generation of relative precipitates. The SEM images indicated that in as-cast alloys, the Al2Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al2Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al11La3 intermetallic compound was located at grain boundaries with a needlelike structure. These intermetallic compounds could reduce the amount of β-Mg17Al12 and refine the microstructure of as-cast AZ91 alloy.

Fracture Modes in Ll2 Compounds

1988 ◽  
Vol 133 ◽  
Author(s):  
C. L. Briant ◽  
A. I. Taub
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Fracture Modes ◽  
Beneficial Effects ◽  
Boron Segregation ◽  
Total Composition ◽  
Carbon Additions

ABSTRACTThis paper reports a study of grain boundary segregation and fracture modes in Ll2 intermetallic compounds. Data obtained on Ni3A1, Ni3Si, Ni3Ga, Ni3Ge, and Pt3Ga will be presented. It will be shown that the amount of boron segregation and its ability to improve cohesion depends on the total composition of the compound. The beneficial effects of boron can be counteracted by the presence of borides on the grain boundaries. Carbon additions also produce some improvement in ductility in Ni3Si.

Mechanisms of ductility improvement in L12 compounds

1988 ◽  
Vol 3 (3) ◽  
pp. 426-440 ◽  
Author(s):  
Osamu Izumi ◽  
Takayuki Takasugi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Present Article ◽  
Electronic Structures ◽  
Alloying Effect ◽  
Test Environment ◽  
Materials Development

The present article first describes some characteristics of structure, chemistry, and electronic (bond) nature for grain boundaries in the A3B Li2-type intermetallic compounds. Next, the phenomenological aspects for the grain boundary brittleness of the Li2-type intermetallic compounds are reviewed with respect to the combination of the constituent atoms, the alloying effect, the stoichiometry effect, and a role of impurity or gaseous atoms. It is emphasized that the brittleness of grain boundaries in the intermetallic compounds is directly controlled by the atomistic and electronic structures at grain boundary regions. Based on these systematic investigations, it is suggested that the brittleness of the Li2-type intermetallic compounds can be manipulated by appropriate control of composition and the corresponding electrochemical bond environment at grain boundary planes and by control of test environment. Furthermore, some examples of the materials development are described.

Formation of a ternary silicide for Ni/Ti/Si (100) and Ni/TiSi2 structures

1989 ◽  
Vol 4 (5) ◽  
pp. 1218-1226 ◽  
Author(s):  
M. Setton ◽  
J. Van der Spiegel ◽  
B. Rothman
Keyword(s):  
Activation Energy ◽  
Phase Separation ◽  
High Temperature ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Ternary Phase ◽  
Metal Silicide ◽  
Mobile Species ◽  
Metal Bilayers ◽  
Ternary Silicide

Phase formation was studied for Ni/Ti/Si and Ni/TiSi2 structures processed by vacuum RTP. Intermetallic compounds Ni3Ti and Ti2Ni form sequentially above 425 °C for metal bilayers Ni/Ti on Si, as Ni diffuses into Ti. When the temperature reaches 550 °C, Si becomes mobile and diffuses into the Ni–Ti compound, resulting in the growth of a ternary phase Ti4Ni4Si7, (V phase). If Ni is in excess with respect to this ternary silicide, a separate layer of Ni silicide grows between the substrate and the V phase, due to the fact that Ni is the main diffusing species. For the case of an excess Ti, the Si atoms are the most mobile species during Ti silicidation. Below 700 °C, TiSi2 grows with a C 49 structure whereas a mixture of TiSi2 C 54 and V phase forms at high temperature, without phase separation in distinct layers. Ni is also a fast diffuser in TiSi2. The activation energy for the diffusion along the grain boundaries of the Ti silicide is about 1.25 ± 0.2 eV. For these Ni/TiSi2 samples too, the same V phase starts to grow at the metal/silicide interface.

Grain Boundaries, Trace Elements, and Fracture of Intermetallic Compounds

1994 ◽  
Vol 364 ◽  
Author(s):  
Hui Lin ◽  
Easo P. George ◽  
David P. Pope
Keyword(s):  
Trace Elements ◽  
Grain Boundaries ◽  
Intermetallic Compounds

Thermal Stress and Texture Development in a Cu/Nb Composite between 4K and 1273 K

2005 ◽  
Vol 495-497 ◽  
pp. 1687-1692
Author(s):  
Wen-Hai Ye ◽  
Hans Georg Priesmeyer ◽  
Heinz Günter Brokmeier
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Research Program ◽  
Linear Accelerator ◽  
Thermal Stresses ◽  
The Other ◽  
Texture Development ◽  
Long Time

Cu-Nb composites are characterized by some special properties, which were discussed since a long time by many different authors [1, 2, 3, and 4]. For manufacturing linear accelerator units it is a great advantage that Cu-Nb don’t form intermetallic compounds. One of the basic questions during application is the influence of the thermal expansion of copper and niobium. Thermal expansion of Cu-Nb was widely discussed by Nadeau and Ferrari [5]. Our research program consists of investigations on Cu50%-Nb50% composites and on Cu-Nb tubes, which on one hand have different textures and on the other hand the grain boundaries are much different in the composite with a curling microstructure and in co-extruded tubes. The present paper will concentrate on thermal stresses and the texture behavior in the temperature range 4K -1273K.

Semi-Solid Processing and Properties of RE-Containing Mg Alloys

2016 ◽  
Vol 256 ◽  
pp. 75-80 ◽  
Author(s):  
Shu Sen Wu ◽  
Xiao Gang Fang ◽  
Shu Lin Lü ◽  
Li Zhao ◽  
Jing Wang
Keyword(s):  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Average Particle Size ◽  
Acoustic Streaming ◽  
Mg Alloys ◽  
Average Particle ◽  
Squeeze Pressure ◽  
Semi Solid ◽  
T Phase ◽  
Zr Alloy

The RE-containing Mg alloys usually have big RE-rich intermetallic compounds distributed along grain boundaries. In this paper, a 3 wt.% RE containing Mg alloy is processed by combination of semi-solid slurry-making with ultrasonic vibration (UV) and squeeze casting. Results show that good semi-solid slurry with fine and spherical primary α-Mg particles can be obtained due to the effects of the cavitation and acoustic streaming induced by UV, and the average particle size and average shape factor are about 30 μm and 0.70 respectively. The RE-rich intermetallic compounds are refined and uniformly distributed along grain boundaries. With the increase of squeeze pressure from 0 MPa to 200 MPa during the casting of semi-solid slurry, the tensile strength and the elongation of the as-cast samples are increased continuously, which reach 182 MPa and 8.4% respectively. The microstructure is also analyzed with SEM, TEM, XRD and EDS, and the phase constitutions of this Mg-RE-Zn-Y-Zr alloy are mainly α-Mg matrix, α-Zr, W phase (Mg3Zn2Y3), I phase (Mg3Zn6Y) and T phase ((La,Ce)(Mg1-xZnx)11). The mechanism of refinement of RE-rich intermetallic compounds is also discussed.

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