Microscale Fracture Toughness Testing of TiAl PST Crystals

2008 ◽  
Vol 1128 ◽  
Author(s):  
Daisuke Miyaguchi ◽  
Masaaki Otsu ◽  
Kazuki Takashima ◽  
Masao Takeyama
Keyword(s):  
Fracture Toughness ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
Type Specimens ◽  
Toughening Mechanisms ◽  
Two Phase ◽  
Fracture Toughness Testing ◽  
Crack Wake ◽  
Toughness Testing

AbstractA microscale fracture testing technique has been applied to examine the fracture properties of lamellar in TiAl PST crystals. Micro-sized cantilever specimens with a size ˜ 10×20×50 μm3 were prepared from Ti-48Al two-phase single crystals (PST) lamellar by focused ion beam (FIB) machining. Notches with a width of 0.5 μm and a depth of 5 μm were also introduced into the specimens by FIB. Two types of notch directions (interlamellar and translamellar) were selected when introducing the notches. Fracture tests were successfully completed using a mechanical testing machine for micro-sized specimens at room temperature. The fracture toughness (KQ) values of the interlamellar type specimens were obtained in the range 1.5–3.6 MPam1/2, while those of the translamellar specimens were 5.0–8.1 MPam1/2. These fracture toughness values are lower than those having been previously reported in conventional TiAl PST samples. For macro-sized specimens, extrinsic toughening mechanisms, including shear ligament bridging, act in the crack wake, and the crack growth resistance increases rapidly with increasing length of crack wake for lamellar structured TiAl alloys. In contrast, the crack length in microsized specimens is only 2–3 μm. This indicates that extrinsic toughening mechanisms are not activated in micro-sized specimens. This also indicates that intrinsic fracture toughness can be evaluated using microscale fracture toughness testing.

Development of Fatigue Pre-Cracking Method into Micro-Sized Specimens for Measuring Fracture Toughness

2002 ◽  
Vol 741 ◽  
Author(s):  
K. Takashima ◽  
S. Koyama ◽  
K. Nakai ◽  
Y. Higo
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
Alloy Thin Film ◽  
Far Field ◽  
Type Specimens ◽  
Beam Type ◽  
Micro Cantilever

ABSTRACTIn our previous investigations [1, 2], we have demonstrated that the introduction of fatigue pre-crack ahead of a notch is required to measure reliable fracture toughness values even for micro-sized specimens. However, it is rather difficult to introduce a fatigue pre-crack into a micro-sized specimen as once a fatigue crack starts to grow then the fatigue fracture occurs within one thousand cycles and this makes it extremely difficult to control fatigue crack length. Therefore, a new fatigue pre-cracking method is required for measuring fracture toughness. In this investigation, a new fatigue pre-cracking method has been proposed for micro-sized specimens and fracture toughness tests were carried out for the micro-sized specimens with fatigue pre-crack. Micro-cantilever beam type specimens with dimensions of 10 × 10 × 50 μm3 were prepared from an electroless deposited Ni-P amorphous alloy thin film and notches were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches by far-field cyclic compression method using a mechanical testing machine for micro-sized specimens (MFT2000). Fracture tests were also carried out using the testing machine. Fatigue pre-cracks with length of 0.2 μm were confirmed on the fracture surfaces ahead of the notches in the far-field cyclically compressed specimens. This indicates that the fatigue pre-cracking method developed in this investigation is promising for measuring accurate fracture toughness for micro-sized specimens for MEMS applications.

The evaluation of the composition dependence of fracture toughness of Al3Nb alloys by using micro-size fracture testing

MRS Advances ◽  
2017 ◽  
Vol 2 (26) ◽  
pp. 1405-1410
Author(s):  
Nobuhiro Matsuzaki ◽  
Ken-ichi Ikeda ◽  
Seiji Miura ◽  
Nobuaki Sekido ◽  
Takahito Ohmura
Keyword(s):  
Fracture Toughness ◽  
Single Crystal ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Two Phase ◽  
Fracture Testing ◽  
Average Value ◽  
Chevron Notch ◽  
Polycrystalline Alloys ◽  
Oxidation Resistant

ABSTRACTAl3Nb is known as a high oxidation resistant material, while it is quite brittle. As the fracture toughness of Al3Nb single crystal and its dependence on the composition are not obtained, the micro-sized fracture testing proposed by Suzuki et al. was performed. Al3Nb single crystal micron-order size cantilevers with a chevron-notch were fabricated in a grain of two-phase polycrystalline alloys by using FIB (Focused Ion Beam). From the load-displacement curves during the bending by a nanoindenter, the average value of fracture toughness of Nb-rich Al3Nb is evaluated to be 2.90 MPam1/2, while the fracture toughness of Al-rich Al3Nb is also evaluated to be 2.82 MPam1/2. From this result, the fracture toughness of Al3Nb is less dependent on its Al/Nb ratio. Furthermore the fracture toughness of Al3 (Nb, V) was evaluated to be 2.82 MPam1/2.The fracture toughness of Al3Nb is seemingly insensitive to V addition.

Fracture Toughness Measurement of a Micro-Sized Single Crystal Silicon

2005 ◽  
Vol 297-300 ◽  
pp. 292-298 ◽  
Author(s):  
Satoru Koyama ◽  
Kazuki Takashima ◽  
Yakichi Higo
Keyword(s):  
Fracture Toughness ◽  
Single Crystal ◽  
Ion Beam ◽  
Testing Machine ◽  
Single Crystal Silicon ◽  
Mems Devices ◽  
Type Specimens ◽  
Crystal Silicon ◽  
Fracture Toughness Measurement ◽  
Toughness Measurement

Reliability is one of the most critical issues for designing practical MEMS devices. In particular, the fracture toughness of micro-sized MEMS elements is important, as micro/nano-sized flaws can act as a crack initiation sites to cause failure of such devices. Existing MEMS devices commonly use single crystal silicon. Fracture toughness testing upon micro-sized single crystal silicon was therefore carried out to examine whether a fracture toughness measurement technique, based upon the ASTM standard, is applicable to 1/1000th sized silicon specimens. Notched cantilever beam type specimens were prepared by focused ion beam machining. Two specimens types with different notch orientations were prepared. The notch plane/direction were (100)/[010], and (110)/[ ＿ ,110], respectively. Fracture toughness tests were carried out using a mechanical testing machine for micro-sized specimens. Fracture has been seen to occur in a brittle manner in both orientations. The provisional fracture toughness values (KQ) are 1.05MPam1/2 and 0.96MPam1/2, respectively. These values meet the micro-yielding criteria for plane strain fracture toughness values (KIC). Fracture toughness values for the orientations tested are of the same order as values in the literature. The results obtained in this investigation indicate that the fracture toughness measurement method used is applicable for micro-sized components of single crystal silicon in MEMS devices.

Micro Fracture Toughness Testing of TiAl Based Alloys with a Fully Lamellar Structure

2004 ◽  
Vol 842 ◽  
Author(s):  
K. Takashima ◽  
T. P. Halford ◽  
D. Rudinal ◽  
Y. Higo ◽  
M. Takeyama
Keyword(s):  
Fracture Toughness ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
High Fracture Toughness ◽  
Fracture Mechanisms ◽  
High Fracture ◽  
Fundamental Information ◽  
Micrometer Scale ◽  
Fully Lamellar

ABSTRACTA micro-sized testing technique has been applied to investigate the fracture properties of lamellar colonies in a fully lamellar Ti-46Al-5Nb-1W alloy. Micro-sized cantilever specimens with a size ≈ 10 × 10 × 50 μm3 were prepared by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 5 μm were also introduced into the micro-sized specimens by focused ion beam machining. Fracture tests were successfully completed using a mechanical testing machine for micro-sized specimens at room temperature. The fracture toughness (KQ) values obtained were in the range 1.4–7 MPam1/2. Fracture surface observations indicate that these variations are attributable to differences in local lamellar orientations ahead of the notch. These fracture toughness values are also lower than those having been previously reported in conventional samples. This may be due the absence of significant extrinsic toughening mechanisms in these micro-sized specimens. Fracture mechanisms of these alloys are also considered on the micrometer scale. The results obtained in this investigation give important and fundamental information on the development of TiAl based alloys with high fracture toughness.

Experiment Research for Fracture Toughness of PAN-Based Carbon Fibers

2011 ◽  
Vol 462-463 ◽  
pp. 1361-1366 ◽  
Author(s):  
Bo Ming Zhang ◽  
Yu Fen Wu
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Carbon Fibers ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
High Strength ◽  
Carbon Filaments ◽  
Fracture Theory ◽  
In Virtue Of

For the sake of the carbon filaments’ fracture toughness, using the focused ion beam (FIB) to etch the carbon fibers and got different tensile strength, and all specimens were stretched on an Instron-type filaments testing machine and got the samples’ tensile strength, The crack-to-mirror size ratio was assumed as a constant, In virtue of Griffith fracture theory, Fracture toughness (KΙC) of representative high-strength type PAN (polyacrylonitrile)-based carbon fibers, Torayca T300 and T800, were estimated to be 1MPam1/2 from the tensile strength vs. fracture mirror size relation.

Fracture Behavior of Micro-Sized Ni-P Amorphous Alloy Specimens

1999 ◽  
Vol 605 ◽  
Author(s):  
Y. Ichikawa ◽  
S. Maekawa ◽  
K. Takashima ◽  
M. Shimojo ◽  
Y. Higo ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Stress Concentration ◽  
Amorphous Alloy ◽  
Fracture Behavior ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
The Other ◽  
Root Radius ◽  
The Difference

AbstractFracture behavior of micro-sized Ni-P Amorphous alloy specimens has been investigated using a newly developed mechanical testing machine. Specimens with dimensions of 10 × 12 × 50 μm were prepared by focused ion beam machining. Two types of specimens with different crack geometries were prepared. One specimen has a notch with root radius is 0.25 μtm and the other has a fatigue pre-crack. The shapes of the loaddisplacement curves are different for each type of specimen. The fracture strength of the specimens with a notch is higher than that with a fatigue pre-crack and the fracture surfaces of the specimens are also different for each type of specimen. This may be due to the difference in stress concentration at the crack (notch) tip, and indicates that even a notch with a root radius of 0.25 μm is not able to be regarded as a crack for micro-sized specimens. Therefore, the introduction of a fatigue pre-crack is essential for the evaluation of fracture toughness for such micro-sized specimens.

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