Fracture Behavior of Micro-Sized Specimens Prepared from a TiAl Thin Foil

2003 ◽  
Vol 795 ◽  
Author(s):  
K. Takashima ◽  
T. P. Halford ◽  
D. Rudinal ◽  
Y. Higo ◽  
P. Bowen
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Testing Machine ◽  
Lamellar Microstructure ◽  
Thin Foil ◽  
Type Specimens ◽  
Thin Foils ◽  
Fracture Tests ◽  
Micro Cantilever ◽  
Fully Lamellar

ABSTRACTFracture tests have been carried out on micro-sized specimens prepared from a fully lamellar γ-TiAl based alloy thin foil. Micro cantilever beam type specimens with dimensions = 50 × 10 × 20 μm were prepared from one lamellar colony of the thin foil by focused ion beam machining. Notches with a width of 0.5 μm and a depth of 10 μm were also introduced into the micro-sized specimens by focused ion beam machining. Notch directions were introduced into samples in order to select the trans- and inter-lamellar directions, respectively. Fracture tests were carried out using a mechanical testing machine for micro-sized specimens. Fracture tests for the micro-sized specimens were performed successfully, showing the fracture behaviour to be dependent upon the notch orientation. The fracture toughness of specimens with a notch direction perpendicular to the lamellar direction was 4.7 – 6.9 MPam1/2, while that with a notch direction in the inter-lamellar direction was 1.4 – 2.7 MPm1/2. This indicates that the orientation of the lamellar microstructure greatly affects the fracture properties of micro-sized components prepared from fully lamellar γ-TiAl based alloy thin foils. It is required to consider the results obtained in this investigation when designing actual micro scale structures using TiAl thin foils.

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.

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.

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.

Fatigue Testing Machine of Micro-Sized Specimens for MEMS Applications

1999 ◽  
Vol 605 ◽  
Author(s):  
Y. Higo ◽  
K. Takashima ◽  
M. Shimojo ◽  
S. Sugiura ◽  
B. Pfister ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Fatigue Testing ◽  
Ion Beam ◽  
Testing Machine ◽  
Load Cell ◽  
Fatigue Properties ◽  
Type Specimens ◽  
New Type ◽  
Beam Type ◽  
Magnetostrictive Actuator

AbstractA new type of fatigue testing machine for micro-sized specimens for MEMS applications has been developed. This fatigue testing machine consists of a magnetostrictive actuator which is able to impart small displacements to a specimen upto 20 νm with resolution of 5 nm. The actuator is connected to a metal shaft and a diamond tip of 5 νm in radius is attached to the end of the shaft. Small displacements are applied to the specimen through the diamond tip. This makes it possible to construct a high stiffness loading fixture. The magnitude of load applied to the specimen is measured by a strain gauge type load cell with a load resolution of 10 νN. The specimen stage and load cell can be moved to adjust the loading position precisely by a stepping motor at a translation resolution of 0.1 νm. Cantilever beam type specimens with dimensions of 10 × 12 × 50 νm3 were prepared from a Ni-P amorphous thin film by focused ion beam machining. Very small cyclic load (ΔP = 0.1 - 40 mN) was able to be applied to the specimen successfully. This machine appears to be promising for evaluation of fatigue properties for micro-sized specimens for MEMS applications.

Microscale Fracture Testing of Mg-Zn-Y

2009 ◽  
Vol 1225 ◽  
Author(s):  
Shun Matsuyama ◽  
Tetsuya Sakamoto ◽  
Masaaki Otsu ◽  
Kazuki Takashima ◽  
Yoshihito Kawamura
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Focused Ion Beam ◽  
Volume Fraction ◽  
Ion Beam ◽  
Testing Machine ◽  
Alloy Specimen ◽  
Testing Technique ◽  
Lpso Phase ◽  
Fracture Tests

AbstractA microfracture testing technique was applied for investigating the fracture properties of Mg-Zn-Y alloys with a long-period stacking ordered (LPSO) phase. Microsized cantilever beam specimens with dimensions ≈ 10×20×50 μm3 were prepared from Mg-Zn-Y alloys by focused ion beam (FIB) machining. Notches with widths of 0.5 μm and depths of 3.5–5 μm were also introduced into the specimens by FIB machining. In this study, three types of Mg-Zn-Y alloys―Mg99.2Zn0.2Y0.6, Mg97Zn1Y2, and Mg88Zn5Y7―were used. Fracture tests were successfully conducted using a mechanical testing machine for microsized specimens at room temperature. The fracture toughness values (KIC) could not be obtained as the specimen size was too small to satisfy the plane strain condition. Hence, provisional KQ values were considered. The KQ values of the Mg97Zn1Y2 alloy were 0.8–1.2 MPam½, and those of the Mg88Zn5Y7 alloy were 1.2–3.0 MPam½. As the fracture in the Mg99.2Zn0.2Y0.6 alloy specimen occurred in a ductile plastic deformation, it was impossible to evaluate KQ values of this specimen. The increasing volume fraction of the LPSO phase indicates that the fracture toughness of Mg-Zn-Y alloys increases in LPSO phase.

Characterisation of Fracture and HAC Resistance of an Individual Microstructural Constituent with Micro-Cantilever Testing

2016 ◽  
Vol 713 ◽  
pp. 66-69
Author(s):  
Walter Costin ◽  
Olivier Lavigne ◽  
Andrei G. Kotousov
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Plastic Hinge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Ferrous Alloys ◽  
Microstructural Constituent ◽  
Macro Scale ◽  
Micro Cantilever ◽  
Hinge Model

This paper focuses on the application of miniaturized fracture tests to evaluate the fracture and hydrogen assisted cracking (HAC) resistance of a selected microstructural constituent (acicular ferrite, AF) which only occurs in microscopic material volumes. Site-specific Focused Ion Beam (FIB) micro-machining was used to fabricate sharply notched micro-cantilevers into a region fully constituting of AF. The micro-cantilevers were subsequently tested under uncharged and hydrogen charged conditions with a nanoindenter. The load displacement curves were recorded and analysed with a simplified plastic hinge model for the uncharged specimen, as AF demonstrated an essentially ductile behaviour. The simplified model assisted with FE simulations provided values of the critical plastic crack tip opening displacement (CTOD). A value of the conditional fracture toughness was thereby determined as 12.1 MPa m1/2. With LEFM, a threshold stress intensity factor, Kth, to initiate hydrogen crack propagation in AF was found to range between 1.56 MPa m1/2 and 4.36 MPa m1/2. All these values were significantly below the corresponding values reported for various ferrous alloys in standard macro-tests. This finding indicates that the fracture and HAC resistance at the micro-scale could be very different than at the macro-scale as not all fracture toughening mechanisms may be activated at this scale level.

scholarly journals MODELING OF MONOCRYSTALLINE MAGNESIUM MICROBEAM BENDING

2018 ◽  
Vol 15 ◽  
pp. 69-73
Author(s):  
Jiří Němeček ◽  
Jan Maňák ◽  
Jiří Němeček
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Deformation Energy ◽  
Displacement Curve ◽  
Fe Model ◽  
Cantilever Beams ◽  
Elastoplastic Behavior ◽  
Load Displacement ◽  
Micro Cantilever

This paper presents a numerical simulation of a micro-scale experiment on a magnesium alloy. Micro cantilever beams were fabricated using Focused Ion Beam technology in a single crystal of Mg. The cantilever beams have dimensions in the order of a few micrometers and a pentagonal cross section. Nanoindenter was used for cantilever beam bending and load-displacement curve was received. Cantilevers with two different crystallographic orientations were chosen for the experiment. Three dimensional numerical FE model with elastoplastic behavior respecting crystal anisotropy was used to fit experimental load displacement curves. Strengths and deformation energy were evaluated from the models for each cantilever.

Effect of gallium focused ion beam milling on preparation of aluminium thin foils

2010 ◽  
Vol 240 (3) ◽  
pp. 227-238 ◽  
Author(s):  
K.A. UNOCIC ◽  
M.J. MILLS ◽  
G.S. DAEHN
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Thin Foils ◽  
Focused Ion Beam Milling

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.

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