Dislocation Morphologies in TiB2/NiAl

1990 ◽  
Vol 194 ◽  
Author(s):  
L. Wang ◽  
R. J. Arsenault
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Nickel Aluminide ◽  
Volume Fraction ◽  
High Temperature Strength ◽  
Matrix Composites ◽  
Annealed Condition ◽  
Low Dislocation Density ◽  
Particulate Form ◽  
Nial Matrix

AbstractThe addition of 20 volume percent titanium diboride in particulate form (1-3 μm) to nickel aluminide (TiB2/NiAl) results in a twofold increase in the high temperature strength of NiAl. Theories that have been proposed to account for the high temperature strength of discontinuous reinforced metal matrix composites can not be adequately used as a basis to explain the observed strengthening.An investigation was undertaken of NiAl, 10 V% TiB2/NiAl and 20 V% TiB2/NiAl in the annealed condition and after deformation, allowed to cool slowly. There is a low dislocation density in the annealed samples and the dislocation density did increase slightly as a result of deformation. However, deformation did produce some intriguing dislocation arrangements; for example, it was found that there was a high dislocation density within the TiB2 in the deformed higher volume fraction composites and the dislocation density within NiAl matrix was not uniform.

Damping and Mechanical Properties of (Graphite + 9Al2O3·2B2O3)/Mg Metal Matrix Composites

2004 ◽  
Vol 449-452 ◽  
pp. 657-660
Author(s):  
Il Dong Choi ◽  
Dong Min Kim ◽  
Kyung Mok Cho ◽  
Ik Min Park
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Damping Capacity ◽  
High Temperature Strength ◽  
Al Alloy ◽  
Matrix Composites ◽  
Graphite Particles

Mg alloys have potential to use automotive parts because of their weight and castability. High temperature strength and damping capacity is important to the automotive power train parts. Mg alloy has lower creep and thermal fatique strength but has better damping capacity than Al alloy. It is known that short fiber reinforced Mg metal matrix composites(MMC) exhibits superior high temperature strength and graphite reinforced Mg MMC shows excellent damping capacity. Therefore, in this study, the effect of graphite particles(15-25%) and alborex (9Al2O3ּ2B2O3) whiskers(5-15%) on the damping behavior and mechanical properties of Mg MMC was studied. Graphite particles and alborex whiskers were chosen to increase damping capacity and high temperature strength, respectively. The Mg MMC was fabricated by squeeze casting and the total quantity of reinforcements(graphite + alborex) was maintained to 30 volume percent. The damping capacity of the metal matrix composites was increased and the flexural strength and hardness were decreased with increasing the volume fraction of graphite particles, that is, reducing the volume fraction of alborex whiskers.

Precipitation of NiHfsi phase in NiAl single crystals containing Hf

1995 ◽  
Vol 53 ◽  
pp. 532-533
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
High Temperature Strength ◽  
Bridgman Technique ◽  
Shell Mold ◽  
Third Phase ◽  
Unknown Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

Microstructural characterization of plasma-processed Ti-Al metal matrix composites

1989 ◽  
Vol 47 ◽  
pp. 552-553
Author(s):  
M. G. Burke ◽  
M. N. Gungor ◽  
M. A. Burke
Keyword(s):  
High Temperature ◽  
Titanium Aluminide ◽  
Plasma Processing ◽  
Microstructural Characterization ◽  
High Temperature Strength ◽  
Matrix Composites ◽  
Intermetallic Matrix ◽  
Long Time ◽  
Strength And Stiffness ◽  
Intermetallic Matrix Composites

Intermetallic matrix composites are candidates for ultrahigh temperature service when light weight and high temperature strength and stiffness are required. Recent efforts to produce intermetallic matrix composites have focused on the titanium aluminide (TiAl) system with various ceramic reinforcements. In order to optimize the composition and processing of these composites it is necessary to evaluate the range of structures that can be produced in these materials and to identify the characteristics of the optimum structures. Normally, TiAl materials are difficult to process and, thus, examination of a suitable range of structures would not be feasible. However, plasma processing offers a novel method for producing composites from difficult to process component materials. By melting one or more of the component materials in a plasma and controlling deposition onto a cooled substrate, a range of structures can be produced and the method is highly suited to examining experimental composite systems. Moreover, because plasma processing involves rapid melting and very rapid cooling can be induced in the deposited composite, it is expected that processing method can avoid some of the problems, such as interfacial degradation, that are associated with the relatively long time, high temperature exposures that are induced by conventional processing methods.

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys with Refractory Alloying Elements

2006 ◽  
Vol 510-511 ◽  
pp. 358-361
Author(s):  
Won Yong Kim ◽  
Han Sol Kim ◽  
In Dong Yeo ◽  
Mok Soon Kim
Keyword(s):  
High Temperature ◽  
Volume Fraction ◽  
Lattice Parameter ◽  
Alloying Elements ◽  
Solid Solution Hardening ◽  
High Temperature Strength ◽  
High Temperature Mechanical Properties ◽  
Die Materials ◽  
The Matrix ◽  
Effective Role

We report on advanced Ni3Al based high temperature structural alloys with refractory alloying elements such as Zr and Mo to be apllied in the fields of die-casting and high temperature press forming as die materials. The duplex microstructure consisting of L12 structured Ni3Al phase and Ni5Zr intermetallic dispersoids was observed to display the microstructural feature for the present alloys investigated. Depending on alloying elements, the volume fraction of 2nd phase was measured to be different, indicating a difference in solid solubility of alloying elements in the matrix γ’ phase. Lattice parameter of matrix phase increased with increasing content of alloying elements. In the higher temperature region more than 973K, the present alloys appeared to show their higher strength compared to those obtained in conventional superalloys. On the basis of experimental results obtained, it is suggested that refractory alloying elements have an effective role to improve the high temperature strength in terms of enhanced thermal stability and solid solution hardening.

The Effect of Alloy Addition on the High Temperature Properties of Over-Aged Al-Si(CuNiMg) Cast Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 461-466 ◽  
Author(s):  
Young Hee Cho ◽  
Dae Heon Joo ◽  
Chul Hyun Kim ◽  
Hu Chul Lee
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Volume Fraction ◽  
Metastable Phase ◽  
Intermetallic Phases ◽  
Alloying Elements ◽  
High Temperature Strength ◽  
Transition Elements ◽  
Cast Alloys ◽  
Equilibrium Phases

The role of alloying elements in the improvement of the high temperature strength of Al-12Si(CuNiMg) cast alloys used for automotive piston applications was investigated. The addition of alloying elements such as Mn, Cr, Ti and Ge was studied and the detailed characterization of the composition and morphology of the constituent phases after over aging at 350 for 1000 hrs was performed. The compositions and volume fractions of the equilibrium phases determined by thermodynamic calculation were compared with the experimental results. The addition of transition elements, including Mn, Cr and Ti, increased the volume fraction of the intermetallic phases, which effectively enhanced the high temperature strength of the alloys. Among these transition elements, Mn turned out to be the most effective alloying element. After adding up to 0.5wt% of Mn, a large number of intermetallic phases, α-Al(Mn,Fe)Si as well as fine Al6(Mn,Fe) particles were precipitated and a significant improvement in the elevated temperature properties was achieved. The addition of Ge promoted the precipitation of the θphase (metastable phase, θ-Al2Cu), due to the formation of GeSi precipitates, thereby improved the mechanical properties of the alloy after T6 heat treatment. However, the presence of these GeSi precipitates did not affect the coarsening of the θ phase to form Qphase( Al5Cu2Mg8Si6) during aging and, thus, the elevated temperature properties were not improved by the addition of Ge.

scholarly journals High Temperature Mechanical Properties and Wear Performance of B4C/Al7075 Metal Matrix Composites

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1108 ◽  
Author(s):  
Sangmin Shin ◽  
Donghyun Lee ◽  
Yeong-Hwan Lee ◽  
Seongmin Ko ◽  
Hyeonjae Park ◽  
...  
Keyword(s):  
High Temperature ◽  
Fracture Mechanism ◽  
Room Temperature ◽  
Volume Fraction ◽  
Microstructural Analysis ◽  
Wear Loss ◽  
Matrix Composites ◽  
Pressing Process ◽  
Liquid Pressing Process ◽  
Al Matrix

In this study, high volume fraction B4C reinforced Al matrix composites were fabricated with a liquid pressing process. Microstructural analysis by scanning electron microscope and a transmission electron microscopy shows a uniform distribution of the B4C reinforcement in the matrix, without any defects such as pore and unwanted reaction products. The compressive strength and wear properties of the Al7075 matrix and the composite were compared at room temperature, 100, 200, and 300 °C, respectively. The B4C reinforced composite showed a very high ultimate compression strength (UCS) over 1.4 GPa at room temperature. The UCS gradually decreased as the temperature was increased, and the UCS of the composite at 300 °C was about one third of the UCS of the composite at room temperature. The fractography of the compressive test specimen revealed that the fracture mechanism of the composites was the brittle fracture mode at room temperature during the compression test. However, at the elevated temperature, AMCs had a mixed mode of a brittle and ductile fracture mechanism under the compressive load. The composite produced by a liquid pressing process also showed superior wear resistance compared with the Al matrix. The result of the wear test indicates that the wear loss of the Al matrix at 300 °C was two times higher than that of the AMCs, which is attributed to the formation of a mechanically mixed layer (MML) in the composites at the high temperature.

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