Transverse Mechanical Behavior of High-Strength Monocarbide Eutectics

1981 ◽  
Vol 12 ◽  
Author(s):  
M.F.X. Gigliotti ◽  
M. R. Jackson ◽  
S. W. Yang ◽  
M. F. Henry ◽  
D. A. Woodford
Keyword(s):  
Mechanical Behavior ◽  
Grain Boundaries ◽  
Fracture Resistance ◽  
High Strength ◽  
Growth Axis ◽  
The Matrix ◽  
Solidification Processes ◽  
Eutectic Systems

Superalloy eutectics strengthened with monocarbide whiskers are highly anisotropic in strength. Mechanical behavior transverse to the growth axis is governed largely by the fracture resistance of the matrix grain boundaries. While the matrices of these eutectics are essentially columnar grained superalloys, there are significant differences between d.s. superalloys and superalloy-monocarbide eutectics. These differences arise, in part from different solidification processes and from the alloying limitations in eutectic systems.

Distribution of Mo at Grain Boundary of 1300MPa CrMo Steel

2005 ◽  
Vol 475-479 ◽  
pp. 109-112
Author(s):  
W.G. Yang ◽  
L.N. Zhang ◽  
X. Zhang ◽  
W.J. Hui
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Fracture Resistance ◽  
High Strength ◽  
Average Content ◽  
Delayed Fracture ◽  
Bonding Force ◽  
Research Results ◽  
Mapping Analysis ◽  
Crmo Steel

TEM, EDS and STEM were used to investigate distribution of Mo element in new CrMo steel ADF1 which is applied to 1300MPa high strength bolts with superior delayed fracture resistance. Research results reveal that Mo easily concentrates at grain boundaries. According to refined EDS point and mapping analysis, the region of Mo segregation at grain boundary is about several nanometers wide, and distribution of Mo along the grain boundary is not uniform. The average content of Mo at grain boundary is about double of that in grain area. Concentration of Mo can increase the bonding force of grain boundary, and this is of advantage to the improvement of strength and delayed fracture resistance of the new CrMo steel.

High Strength Mg-Zn-Y-Ce-Zr Alloy Bars Prepared by RS and Extrusion Technology

2005 ◽  
Vol 488-489 ◽  
pp. 495-498 ◽  
Author(s):  
Xuefeng Guo ◽  
Jacob Kinstler ◽  
Lilia Glazman ◽  
Dan Shechtman
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Submicron Particles ◽  
Commercial Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Matrix ◽  
Extrusion Technology ◽  
Scanning Electron ◽  
Zr Alloy

Based on the commercial alloy ZK60 which contains 6%Zn, high strength Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr magnesium alloy bars of 10 to 50 mm in diameters were prepared by rapid solidification (RS) and extrusion processes （RSE）. For those RSE solid bars, the ultimate tensile strengths steadily maintain on a level of 490 to 520 MPa, the elongations are between 6 to 10%. The HV50 hardness is between 85 and 90. In order to reveal materials microstructures both RS ribbons and RSE solid bars, the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy was analyzed with an optical microscopy (OM), a scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an X-ray diffraction apparatus. It was found that the microstructure of the RS ribbon consists of super saturated (Mg) solid solution; thermally stable Mg3Y2Zn3 (W) and Mg7Ce2 intermetallic compound particles which uniformly dispersed interior grains and W and Mg7Ce2 compound networks at grain boundaries. After extrusion, the microstructure of RSE Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr solid bar consists of the same phases as the RS ribbons. The networks existing at RS ribbon’s grain boundaries were break up into submicron particles and dispersed uniformly on the matrix formed after extrusion.

Effect of Heat Treatment Conditions on Microstructures and Mechanical Properties of Cu-9Ni-6Sn-0.22Nb Alloy

2021 ◽  
Vol 904 ◽  
pp. 124-130
Author(s):  
Si Yang Xu ◽  
Ying Long Li ◽  
Mu Xin Zhang ◽  
Yi Fu Jiang ◽  
Hua Ding
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Electrical Conductivity ◽  
Grain Boundaries ◽  
Spinodal Decomposition ◽  
Ageing Time ◽  
High Strength ◽  
Ageing Temperature ◽  
Treatment Conditions ◽  
The Matrix

Due to its high strength, excellent electrical conductivity and high resistance to stress corrosion, Cu-Ni-Sn alloy has been selected as a kind of advanced metal material which can be used as the manufacture of springs, connectors, bearings and so on. In addition, the addition of Nb can efficiently improve the comprehensive properties of the alloy. In the present work, the effect of heat treatment conditions on microstructure and mechanical properties were studied in a Cu-9Ni-6Sn-0.22Nb alloy by means of optical microscopy (OM), transmission electron microscopy (TEM), tensile test and microhardness tests. The results show that before ageing, a large number of fine γ precipitates with DO22 type structure are distributed on the matrix. With the prolongation of ageing time, the ultimate tensile strength (UTS), yield strength (YS) and Vickers hardness increased firstly, and then decline. The reason can be attributed to the occurrence of spinodal decomposition and the formation of discontinuous precipitation (DP). At first, spinodal decomposition induced the enhanced interaction between dislocations and internal stress field, resulting in an increase of mechanical properties. Then the increased DP at grain boundaries leads to the decline of strength in the material. Finally, the relationship between the microstructure and the electrical conductivity was also analyzed, and the results show that the electrical conductivity increased with ageing time/ageing temperature increasing for the present alloy. Through the analysis of Matthiessen’ s rule, the variation of electrical resistivity depends on precipitates, solute atoms, dislocations, vacancies and grain boundaries, and the precipitates play an important role among them. Besides, more precipitates improve electrical conductivity. Therefore, the increase of ageing time/ageing temperature induced the increase of DP, resulting in an increase of electrical conductivity.

Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Diffraction effects from inclined grain boundaries in polycrystalline thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 420-421
Author(s):  
C.B. Carter ◽  
A.M. Donald ◽  
S.L. Sass
Keyword(s):  
Thin Film ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Foil Surface ◽  
Thin Foils ◽  
The Matrix ◽  
Firm Basis ◽  
Diffraction Patterns ◽  
Wave Matching ◽  
Diffraction Effects

Using thin-film gold bicrystals with the boundary plane parallel to the foil surface, it has been shown(l,2) that networks of grain boundary dislocations can act as diffraction gratings and give rise to subsidiary reflections close to the matrix reflections in electron diffraction patterns. Recently several groups of workers(3-5) have shown that inclined boundaries in polycrystalline specimens also produce extra reflections which may be due to the periodic nature of the boundaries. In general grain boundaries in polycrystalline specimens will be steeply inclined to the foil surface and additional reflections due to wave matching at the boundary(6) will also be present. The diffraction technique has the potential for providing detailed information on the structure of inclined boundaries (see, for example (5)), especially for the case where the image contains no useful information. In order to provide a firm basis for this technique, the geometry of the diffraction effects expected from inclined boundaries and the influence of these effects on the appearance of images will be examined.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

Precipitation on Low Angle Boundaries in Al-Zn-Mg

1980 ◽  
Vol 38 ◽  
pp. 374-375
Author(s):  
Diane M. Vanderwalker
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Boundary Structure ◽  
Aircraft Industry ◽  
Precipitate Free Zone ◽  
High Angle ◽  
Adjacent Region ◽  
Free Zone ◽  
Widespread Interest

There is a widespread interest in understanding the properties of Al-base alloys so that progress can be made toward extending their present applications in the aircraft industry. Al-Zn-Mg is precipitation hardened to gain its high strength; however, during aging the formation of heterogeneous precipitates on the grain boundaries creates a precipitate-free zone in the adjacent region. Since high angle grain boundaries are not easily characterized, it is difficult to establish a relationship between the precipitate and the boundary structure. Therefore, this study involves precipitation on low angle grain boundaries where the boundary and the precipitate can be fully analyzed.

Effect of High Strength Structural Steel Structural State on Fracture Resistance

Metallurgist ◽  
2021 ◽  
Author(s):  
V. N. Zikeev ◽  
O. N. Chevskaya ◽  
A. R. Mishet’yan ◽  
V. G. Filippov ◽  
A. B. Korostelev
Keyword(s):  
Structural Steel ◽  
Structural State ◽  
Fracture Resistance ◽  
High Strength

MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg-Ag ALLOY WITH TRACE Zr ADDITION DURING TWO-STEP HOMOGENIZATION

2009 ◽  
Vol 23 (06n07) ◽  
pp. 855-862 ◽  
Author(s):  
FEIYUE MA ◽  
ZHIYI LIU
Keyword(s):  
Melting Point ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Cast Alloy ◽  
Scanning Calorimetry ◽  
Zr Addition ◽  
Homogenization Time ◽  
The Matrix ◽  
Higher Temperature ◽  
Lower Temperature

The microstructural evolution in an Al - Cu - Mg - Ag alloy with trace Zr addition during homogenization treatment was characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). It was shown that the low-melting-point phase segregating toward grain boundaries is Al 2 Cu , with a melting point of 523.52°C. A two-step homogenization process was employed to optimize the microstructure of the as-cast alloy, during which the alloy was first homogenized at a lower temperature, then at a higher temperature. After homogenized at 420°C for 6 h, Al 3 Zr particles were finely formed in the matrix. After that, when the alloy was homogenized at an elevated temperature for a longer time, i.e., 515°C for 24 h, most of the precipates at the grain boundaries were removed. Furthermore, the dispersive Al 3 Zr precipitates were retained, without coarsening greatly in the final homogenization step. A kinetics model is employed to predict the optimal homogenization time at a given temperature theoretically, and it confirms the result in present study, which is 420°C/6h+515°C/24h.

Microstructures and Mechanical Behavior of Bulk Nanocrystalline γ–Ni–Fe Produced by a Mechanochemical Method

2002 ◽  
Vol 17 (5) ◽  
pp. 991-1001 ◽  
Author(s):  
X. Y. Qin ◽  
J. S. Lee ◽  
C. S. Lee
Keyword(s):  
Yield Strength ◽  
Mechanical Behavior ◽  
Light Emission ◽  
Hot Isostatic Pressing ◽  
Microstructural Analysis ◽  
High Strength ◽  
Compression Tests ◽  
Mechanochemical Method ◽  
Force Microscopy ◽  
Bulk Nanocrystalline

The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.

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