scholarly journals GRAIN BOUNDARY STRUCTURE AND MECHANICAL PROPERTIES OF THE TiAl INTERMETALLIC COMPOUND

1990 ◽  
Vol 51 (C1) ◽  
pp. C1-519-C1-524
Author(s):  
R. M. IMAYEV ◽  
G. A. SALISHCHEV
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compound ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Tial Intermetallic Compound

On the Role of Grain-Boundary Films in Optimizing the Mechanical Properties of Silicon Carbide Ceramics

2004 ◽  
Vol 818 ◽  
Author(s):  
R. O. Ritchie ◽  
X.-F. Zhang ◽  
L. C. De Jonghe
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Carbide ◽  
Grain Boundary ◽  
Elevated Temperatures ◽  
Boundary Structure ◽  
Intergranular Films ◽  
Grain Boundary Structure ◽  
Silicon Carbide Ceramics

AbstractThrough control of the grain-boundary structure, principally in the nature of the nanoscale intergranular films, a silicon carbide with a fracture toughness as high as 9.1 MPa.m1/2 has been developed by hot pressing β-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations. In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features. Elongated SiC grains with 1 nm-wide amorphous intergranular films were believed to be responsible for the in situ toughening of this material, specifically by mechanisms of crack deflection and grain bridging. Two methods were found to be effective in modifying microstructure and optimizing mechanical performance. First, prescribed post-annealing treatments at temperatures between 1100 and 1500°C were seen to cause full crystallization of the amorphous intergranular films and to introduce uniformly dispersed nanoprecipitates within SiC matrix grains; in addition, lattice diffusion of aluminum at elevated temperatures was seen to alter grain-boundary composition. Second, adjusting the nominal content of sintering additives was also observed to change the grain morphology, the grain-boundary structure, and the phase composition of the ABC-SiC. In this regard, the roles of individual additives in developing boundary microstructures were identified; this was demonstrated to be critical in optimizing the mechanical properties, including fracture toughness and fatigue resistance at ambient and elevated temperatures, flexural strength, wear resistance, and creep resistance.

Influence of Annealing on the Microstructure and Mechanical Properties of Electrodeposited Nanocrystalline Nickel

2011 ◽  
Vol 683 ◽  
pp. 103-112 ◽  
Author(s):  
B. Yang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Boundary State ◽  
Microstructure And Mechanical Properties ◽  
Grain Boundary Structure ◽  
Average Grain Size ◽  
Different Grain Size

The evolution of the microstructure and mechanical properties of electrodeposited nanocrystalline Ni with different annealing procedures was studied systematically. For the annealed specimens hardness decreases with increasing average grain size but the dependence changes at different grain size ranges. The specimens annealed at a low temperature show higher hardness compared to the as-deposited nanocrystalline Ni, despite an increased measured average grain size. In association with this hardening an increase in elastic modulus and a decrease in microstrain was observed after annealing. With increasing annealing temperature both the tensile strength and the fracture strain were observed to decrease, this is companied with a transition from ductile to brittle in the fracture surfaces. These results indicated that the mechanical behaviour of nanocrystalline Ni depends not only on the average grain size but also on the grain boundary structure. A change in the grain boundary state arising from annealing may be responsible for the observed increase in hardness and elastic modulus as well as the deterioration of tensile properties.

Mechanism of Surface Dissolution in Dense Hydroxyapatite

2007 ◽  
Vol 121-123 ◽  
pp. 1241-1244 ◽  
Author(s):  
Dong Seok Seo ◽  
Hwan Kim ◽  
Jong Kook Lee
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Xrd Analysis ◽  
Boundary Structure ◽  
Molar Ratio ◽  
Dissolution Mechanism ◽  
Grain Boundary Structure ◽  
High Resolution Tem ◽  
Moisture Protection

In this study, it was demonstrated how second phases with small amount, which are hardly detected by XRD analysis, affect grain boundary dissolution and related mechanical properties of HA. All HA disks sintered at 1200 oC for 2 h in air with under moisture protection were phase pure and had Ca/P molar ratio of 1.67. Following certain period of exposure to the distilled water, the surface dissolution initiated at grain boundaries and particle loosening, subsequently resulting in decrease in mechanical properties of HA. In order to understand the dissolution mechanism, grain boundary structure of HA was identified by transmission electron microscopy (TEM) and high resolution TEM observation. From the analysis, it was found that the non-stoichiometric phase as α-tricalcium phosphate (TCP) transformed from β-TCP was existed at grain boundaries and caused surface dissolution of HA. From the XRD analysis, it was found that (211) and (112) planes of hydroxyapatite were susceptible to dissolution, whereas (300) plane was relatively stable.

Effect of CoO Doping on the Sintering Ability and Mechanical Properties of Y-TZP

2004 ◽  
Vol 449-452 ◽  
pp. 265-268 ◽  
Author(s):  
Tetsuhiko Onda ◽  
H. Yamauchi ◽  
Motozo Hayakawa
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Refinement ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Tetragonal Zirconia ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Boundary Strength

The effect of CoO addition into Y-TZP (Yttria doped Tetragonal Zirconia Polycrystals) was studied on the evolution of its sintering ability, grain size, grain boundary structure and mechanical properties. The doping of a small amount of CoO effectively reduced the sintering temperature. A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth. The hardness and toughness of the CoO doped TZP were about the same as those of undoped TZP. Furthermore, despite the grain refinement, CoO doped TZP did not exhibit improved mechanical properties. This may be suggesting that CoO dopant had weakened the grain boundary strength.

Mechanical properties of nanocrystalline and epitaxial TiN films on (100) silicon

2001 ◽  
Vol 16 (9) ◽  
pp. 2733-2738 ◽  
Author(s):  
H. Wang ◽  
A. Sharma ◽  
A. Kvit ◽  
Q. Wei ◽  
X. Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Single Crystal ◽  
Grain Boundary Sliding ◽  
Boundary Structure ◽  
Triple Junctions ◽  
Tin Films ◽  
Grain Boundary Structure ◽  
Transmission Electron

We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate temperature from 25 to 700 °C during pulsed laser deposition, the microstructure of TiN films changed from nanocrystalline (having a uniform grain size of 8 nm) to a single crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffraction and high-resolution transmission electron microscopy. Hardness measurements were made using nanoindentation techniques. The nanocrystalline TiN contained numerous triple junctions without any presence of amorphous regions. The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sliding, which is particularly relevant in the case of hard materials such as TiN.

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