Room Temperature Tensile Ductility in Powder Processed B2 FeAi Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
M. A. Crimp ◽  
K. M. Vedula ◽  
D. J. Gaydosh
Keyword(s):  
Fracture Surface ◽  
Yield Strength ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Yield Stress ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Strengthening Mechanism ◽  
General Yielding

AbstractIt has been shown that it is possible to obtain significant room temperature tensile ductility in FeAl alloys using iron-rich deviations from stoichiometry. A comparison of the room temperature tensile and compressive behaviors of Fe−50at% Al and Fe−40at% Al shows that FeAl is brittle at higher Al contents because it fractures along grain boundaries before general yielding. Lower aluminium contents reduce the yield stress substantially and hence some ductility is observed before fracture.Addition of boron results in measurable improvements in ductility of Fe−40at% Al and is accompanied by an increase in transgranular tearing on the fracture surface, suggesting a grain boundary strengthening mechanism.Increasing the cooling rate following annealing at 1273 K results in a large increase in the yield strength and a corresponding decrease in ductility.

EFFECT OF Al ON MICROSTRUCTURE AND PROPERTIES OF In718 ALLOY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1066-1073
Author(s):  
FANG LIU ◽  
SHULIN YANG ◽  
WENRU SUN ◽  
SHOUREN GUO ◽  
ZHUANGQI HU
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Sharp Decrease ◽  
Compact Form ◽  
Phase Precipitation ◽  
Σ Phase ◽  
Δ Phase

Compared with the conventional In 718 alloy, the addition of Al at the level of 1.24% and 1.50% greatly increases the precipitation of γ′ phase and the compact form of γ″/γ′/γ″ structure, which has been demonstrated in previous studies. The δ phase precipitation at the grain boundaries is noticeably suppressed. Large amount of Laves phase (( Fe , Ni , Cr )2( Nb , Mo )), small amount of M 7 C 3 carbide and σ phase (( Fe , Ni )( Cr , Mo , Nb )) are precipitated at the grain boundaries. After aging at 680°C, the grain boundary precipitates are increased significantly. Large amount needle-like σ phase is precipitated at the grain boundary in the alloy with 1.50% Al . After aging at 680°C for 1000h, the grain boundary precipitates are worsened further, but the coarsening of the compact form γ″/γ′/γ″ is lighter than the γ″ phase in the normal In 718 alloy. The tensile strength at room temperature and 680°C are increased due to Al increasing. While the tensile ductility and impact toughness of the alloy decrease significantly, and a sharp decrease has been found during the long term aging at 680°C. The mechanism by which Al influencing the microstructure and mechanical properties of In 718 alloy is to be discussed.

Room Temperature Tensile Ductility in Polycrystalline B2 NiAl

1988 ◽  
Vol 133 ◽  
Author(s):  
K. Vedula ◽  
K. H. Hahn ◽  
B. Boulogne
Keyword(s):  
Yield Strength ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Lower Yield ◽  
Polycrystalline Alloys ◽  
Lower Yield Strength ◽  
Stoichiometric Alloy

ABSTRACTBinary polycrystalline alloys of B2 NiAl, ranging from 47 to 51.5 at% Al, were prepared by casting and extrusion. These were tested in tension at temperatures ranging from 300 K to 873 K. Significant tensile ductility is observed in the near-stoichiometric alloy at room temperature as well as at 473 K in spite of the presence of only <100> dislocations. This anomaly appears to be related to the recrystallized texture, to the lower yield strength and to the presence of residual dislocations at grain boundaries in this alloy.

Brittle fracture and grain boundary chemistry of microalloyed NiAl

1990 ◽  
Vol 5 (4) ◽  
pp. 754-762 ◽  
Author(s):  
E. P. George ◽  
C. T. Liu
Keyword(s):  
Solid Solution ◽  
Yield Strength ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Fracture Mode ◽  
Tensile Ductility ◽  
Hard Sphere Model ◽  
Strengthening Effect ◽  
Boundary Chemistry

The room-temperature tensile properties, fracture mode, and grain boundary chemistry of undoped stoichiometric NiAl, as well as NiAl doped with boron, carbon, and beryllium, have been investigated, Pure, stoichiometric NiAl fractures with limited tensile ductility in a predominantly intergranular manner. Auger analyses revealed that the grain boundaries in NiAl are extremely clean and free of any segregated impurities, indicating that they are intrinsically brittle. Boron, when added to stoichiometric NiAl at a bulk level of 300 wt. ppm, segregates to the grain boundaries and suppresses intergranular fracture. However, there is no attendant improvement in tensile ductility because boron is an extremely potent solid solution strengthener in NiAl, more than doubling its yield strength. As a result, any potential benefit of improving grain boundary strength is more than offset by the increase in yield strength. Unlike boron, both carbon (300 ppm) and beryllium (500 ppm) are ineffective in suppressing intergranular fracture in NiAl, and Auger analyses of the C-doped alloy revealed that carbon did not affect the fracture mode because it did not segregate to the grain boundaries. Although neither beryllium nor carbon suppressed grain boundary fracture, their effects on the tensile ductility of NiAl were quite different: the ductility of the Be-doped alloy was higher than that of the B-doped alloy because beryllium, unlike boron, has a rather modest strengthening effect in NiAl, whereas the C-doped alloy was brittle like the B-doped alloy, because carbon is a potent solid solution strengthener, just like boron. These observations were rationalized by considering a hard-sphere model for interstitial and substitutional sites in NiAl. It was concluded that boron and carbon occupy interstitial sites, whereas beryllium dissolves substitutionally. In all the alloys that were investigated, the Ni and Al contents of the grain boundaries were not significantly different from the bulk levels, and no evidence was found for B–Ni cosegregation.

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

scholarly journals Microstructure and Enhanced Properties of Copper-Vanadium Nanocomposites Obtained by Powder Metallurgy

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 339 ◽  
Author(s):  
Yong Wang ◽  
Jinguo Wang ◽  
Haohao Zou ◽  
Yutong Wang ◽  
Xu Ran
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Yield Strength ◽  
Grain Boundary ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Copper Matrix ◽  
Dispersion Strengthening ◽  
Annealed Copper ◽  
Grain Boundary Strengthening

Cu-2.4 wt.%V nanocomposite has been prepared by mechanical alloy and vacuum hot-pressed sintering technology. The composites were sintered at 800 °C, 850 °C, 900 °C, and 950 °C respectively. The microstructure and properties of composites were investigated. The results show that the Cu-2.4 wt.%V composite presents high strength and high electrical conductivity. The composite sintered at 900 °C has a microhardness of 205 HV, a yield strength of 404.41 MPa, and an electrical conductivity of 79.5% International Annealed Copper Standard (IACS); the microhardness and yield strength reduce gradually with the increasing consolidation temperature, which is mainly due to the growth of copper grain size. After sintering, copper grain size and V nanoparticle both maintain in nanoscale; the strengthening mechanism is related to grain boundary strengthening and dispersion strengthening, while the grain boundary strengthening mechanism plays the most important role. This study indicates that the addition of small amounts of V element could enhance the copper matrix markedly with the little sacrifice of electrical conductivity.

Effect of Forging Temperature on Microstructure and Tensile Properties in Fe3Al-Based Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
Y. Yang ◽  
W. Yan ◽  
J. N. Liu ◽  
S. Hanada
Keyword(s):  
Plastic Deformation ◽  
Low Temperature ◽  
Yield Strength ◽  
Grain Boundaries ◽  
Tensile Properties ◽  
Room Temperature ◽  
Annealing Treatment ◽  
Different Temperatures ◽  
Local Plastic Deformation ◽  
Strength And Ductility

AbstractForging processes at two different temperatures are performed to examine the relation between the microstructure and room temperature tensile properties in a Ce doped Fe3Al-based alloy. Results show that the microstructure and the ductility are sensitive to the forging temperature before annealing treatment. Higher yield strength and ductility can be obtained through forging at a relatively low temperature of 750°C followed by annealing at 800°C and 500°C. It is suggested that the formation of non-equilibrium grain boundaries and banded subgrains within carbide-free areas along grain boundaries enhances the local plastic deformation and results in the improvement of ductility. During the initial deformation at room temperature <111> slip is predominant for both microstructures.

Precipitation of Copper and Cobalt at Grain Boundaries in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
U. Jendrich ◽  
H. J. Möller
Keyword(s):  
Particle Size ◽  
Mössbauer Spectroscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Cooling Rate ◽  
Polycrystalline Silicon ◽  
Mossbauer Spectroscopy ◽  
Low Energy ◽  
Surface Source ◽  
Mößbauer Spectroscopy

AbstractThe precipitation of copper and (radioactive) cobalt at low energy grain boundaries in polycrystalline silicon and bicrystals is investigated. The metals are diffused in from a surface source between 800 - 1000 °C and the precipitation after cooling down is studied by TEM (for Cu) and Mößbauer spectroscopy (for Co). The precipitates are metal suicides. For copper it is shown that they appear in form of colonies containing hundreds of precipitates with a particle size between 5-60 nm. In the grain boundary they nucleate preferentially at dislocations and steps. The distribution and size of the precipitates depend on the cooling rate after the diffusion. In the vicinity of the grain boundary the volume is depleted from the impurities.

Ductilization of a Ni3(Si,Ti) Intermetallic Alloy by Addition of Interstitial Type Elements

2011 ◽  
Vol 409 ◽  
pp. 321-326
Author(s):  
Hisashi Kosaka ◽  
Yasuyuki Kaneno ◽  
Takayuki Takasugi
Keyword(s):  
Fracture Surface ◽  
Fracture Mode ◽  
Room Temperature ◽  
Tensile Ductility ◽  
Tensile Elongation ◽  
Intermetallic Alloy ◽  
Intermediate Temperature ◽  
Transgranular Fracture ◽  
Ti Alloy ◽  
Brittle Intergranular Fracture

The effect of a concomitant doping of interstitial type elements boron (B) and carbon (C), and boron (B) and nitrogen (N) on tensile properties of a Ni3(Si,Ti) intermetallic alloy was investigated in the temperature range between room temperature and 973 K. It was found that the concomitant doping of (C/B) and (N/B) remarkably improved the intermediate-temperature tensile elongation of the Ni3(Si,Ti) alloy compared with the simple doping of B or C. It was also shown that the fracture surface of the alloy doped with (C/B) and (N/B) exhibited the ductile transgranular fracture mode while that of the alloy doped with only B showed a brittle intergranular fracture mode at 773 K. These results clearly indicate that the concomitant doping of the interstitial type elements are useful for improving the intermediate-temperature tensile ductility of the Ni3(Si,Ti) alloy.

scholarly journals Design and Synthesis of C-O Grain Boundary Strengthening of Al Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 438
Author(s):  
Jianian Hu ◽  
Jian Zhang ◽  
Guoqiang Luo ◽  
Yi Sun ◽  
Qiang Shen ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Grain Boundary ◽  
Pure Aluminum ◽  
Polyvinyl Butyral ◽  
Strengthening Mechanism ◽  
Vertical Tube ◽  
Al Matrix ◽  
Grain Boundary Strengthening

This research presents an approach for C-O grain boundary strengthening of Al composites that used an in situ method to synthesize a C-O shell on Al powder particles in a vertical tube furnace. The C-O reinforced Al matrix composites (C-O/Al composites) were fabricated by a new powder metallurgy (PM) method associated with the hot pressing technique. The data indicates that Al4C3 was distributed within the Al matrix and an O-Al solution was distributed in the grain boundaries in the strengthened structure. The formation mechanism of this structure was explained by a combination of TEM observations and molecular dynamic simulation results. The yield strength and ultimate tensile strength of the C-O/Al composites, modified by 3 wt.% polyvinyl butyral, reached 232.2 MPa and 304.82 MPa, respectively; compared to the yield strength and ultimate tensile strength of the pure aluminum processed under the same conditions, there was an increase of 124% and 99.3%, respectively. These results indicate the excellent properties of the C-O/Al-strengthened structure. In addition, the strengthening mechanism was explained by the Hall–Petch strengthening, dislocation strengthening, and solid solution strengthening mechanisms, which represented contributions of nearly 44.9%, 15.9%, and 16.6% to the total increased strength, respectively. The remaining increment was attributed to the coupled strengthening of the C and O, which contributed 20.6% to the total increase.

Effect of hafnium addition on a Ni-Al-Co Alloy

1990 ◽  
Vol 48 (4) ◽  
pp. 940-941
Author(s):  
L. S. Lin ◽  
G. W. Levan ◽  
S. M. Russell ◽  
C. C. Law
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Yield Strength ◽  
Grain Boundaries ◽  
Ternary Alloy ◽  
Room Temperature ◽  
Gamma Prime ◽  
Room Temperature Ductility ◽  
Appreciable Increase ◽  
Hf Addition

Recent efforts at P&W have shown that the addition of cobalt to binary NiAl results in an appreciable increase in room temperature ductility. One version of this ternary alloy, designated VIM A, has a composition of Ni-30 at.% Al-35 at.% Co. The addition of 0.5 at.% Hf to this alloy (designated VIM AH) results in an improvement in yield strength at 760°C. Room temperature properties were not found to be significantly affected by the Hf addition. This discussion will focus on the microstructures of alloys VIM A and VIM AH and their relationship to the mechanical properties observed in compression at room temperature and 760°C.The addition of hafnium reduced the grain size of VIM AH alloy. After room temperature compression, both alloys show an ordered bcc (B2) matrix and precipitates which are distributed primarily along grain boundaries. These precipitates were identified by microdiffraction to be ordered fcc (L12) gamma prime for VIM A and hexagonal (A3) for VIM AH.

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