Fracture Behavior of Micro-Sized Specimens Prepared From an Amorphous Alloy Thin Film at Ambient and Elevated Temperatures

2001 ◽  
Vol 695 ◽  
Author(s):  
K. Takashima ◽  
R. Tarumi ◽  
Y. Higo
Keyword(s):  
Thin Film ◽  
Fracture Toughness ◽  
Amorphous Alloy ◽  
Cantilever Beam ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Alloy Thin Film ◽  
Type Specimens ◽  
Beam Type

ABSTRACTFracture behavior of micro-sized cantilever beam type specimens prepared from an electroless deposited Ni-P amorphous alloy thin film has been investigated at ambient and elevated temperatures. Cantilever beam type specimens with dimensions of 10 x 12 x 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. The introduction of fatigue pre-crack and fracture toughness tests were carried out using a mechanical testing machine for micro-sized specimens. The temperature of the specimen was controlled from room temperature to 473 K using a newly developed heating system. Compared with room temperature, fracture toughness increased approximately 40 % at 373 K but decreased 19 % at 473 K. The increase of fracture toughness at 373 K is considered to be related with the formation of nano-sized crystals and the decrease of fracture toughness at 473 K is considered to be due to the growth of crystals. It is required to consider the fracture behavior obtained in this investigation when designing actual MEMS devices using electroless deposited amorphous films.

Anisotropic Fracture Behavior of Electroless deposited Ni-P Amorphous Alloy Thin Films

2000 ◽  
Vol 657 ◽  
Author(s):  
Kazuki Takashima ◽  
Akio Ogura ◽  
Yusuke Ichikawa ◽  
Yakichi Higo
Keyword(s):  
Thin Film ◽  
Amorphous Alloy ◽  
Crack Propagation ◽  
Fracture Behavior ◽  
Growth Direction ◽  
Propagation Direction ◽  
Alloy Thin Film ◽  
Anisotropic Fracture ◽  
Crack Propagation Direction ◽  
Fracture Tests

ABSTRACTFracture tests have been carried out for an electroless deposited Ni-P amorphous alloy thin film with different crack growth directions. Cantilever beam type specimens with dimensions of 10 × 10 × 50 μm3 were prepared from a Ni-P amorphous thin film and notches with different directions, which are perpendicular and parallel to the deposition growth direction, were introduced by focused ion beam machining. Fatigue pre-cracks were introduced ahead of the notches. Fracture tests were performed using a mechanical testing machine for micro-sized specimens. Fracture behavior is different between the two types of specimens. As KIC values were not obtained because the criteria of plane strain were not satisfied for this size of the specimen, the provisional fracture toughness KQ values were determined. The KQ value of the specimen with crack propagation direction being perpendicular to the deposition growth direction was 4.2 MPam1/2, while that with crack propagation direction being parallel to the deposition growth direction was 7.3 MPam1/2. This result suggests that the electroless deposited Ni-P amorphous alloy thin film has anisotropic fracture properties.

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.

Ductility and Fracture Behavior of Polycrystalline Ni3Al Alloys

1986 ◽  
Vol 81 ◽  
Author(s):  
C. T. Liu
Keyword(s):  
Fracture Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Grain Shape ◽  
Tensile Ductility ◽  
Dynamic Effect ◽  
Al Alloys ◽  
Gaseous Oxygen ◽  
Comprehensive Review ◽  
Room Temperature Ductility

AbstractThis paper provides a comprehensive review of the recent work on tensile ductility and fracture behavior of Ni3AI alloys tested at ambient and elevated temperatures. Polycrystalline Ni3Al is intrinsically brittle along grain boundaries, and the brittleness has been attributed to the large difference in valency, electronegativity, and atom size between nickel and aluminum atoms. Alloying with B, Mn, Fe, and Be significantly increases the ductility and reduces the propensity for intergranular fracture in Ni3 Al alloys. Boron is found to be most effective in improving room-temperature ductility of Ni3Al with <24.5 at. % Al.The tensile ductility of Ni3Al alloys depends strongly on test environments at elevated temperatures, with much lower ductilities observed in air than in vacuum. The loss in ductility is accompanied by a change in fracture mode from transgranular to intergranular. This embrittlement is due to a dynamic effect involving simultaneously high localized stress, elevated temperature, and gaseous oxygen. The embrittlement can be alleviated by control of grain shape or alloying with chromium additions. All the results are discussed in terms of localized stress concentration and grain-boundary cohesive strength.

The Room Temperature and Elevated Temperature Fracture Toughness Response of Alloy A-286

1978 ◽  
Vol 100 (2) ◽  
pp. 195-199 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Surface Micromorphology ◽  
Second Phase Particles ◽  
The Matrix ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Base Superalloy

The elastic-plastic fracture toughness (JIc) response of precipitation strengthened Alloy A-286 has been evaluated by the multi-specimen R-curve technique at room temperature, 700 K (800°F) and 811 K (1000°F). The fracture toughness of this iron-base superalloy was found to decrease with increasing temperature. This phenomenon was attributed to a reduction in the materials’s strength and ductility at elevated temperatures. Electron fractographic examination revealed that the overall fracture surface micromorphology, a duplex dimple structure coupled with stringer troughs, was independent of test temperature. In addition, the fracture resistance of Alloy A-286 was found to be weakened by the presence of a nonuniform distribution of second phase particles throughout the matrix.

Deformation Behavior of Polycrystalline AZ31 Alloy at Room and Elevated Temperatures

2005 ◽  
Vol 488-489 ◽  
pp. 775-778
Author(s):  
Tsing Zhou ◽  
Goroh Itoh ◽  
Yohei Iseno ◽  
Yoshinobu Motohashi
Keyword(s):  
Deformation Behavior ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Az31 Alloy ◽  
Slip Systems ◽  
Type Specimens ◽  
Rolled Specimen ◽  
Hot Rolled

The hot-rolled and extruded AZ31 specimens are subjected to tensile tests at room and elevated temperatures. At room temperature, the yield stress of the hot-rolled specimen is significantly higher than that of the extruded, the reason for which is related to the different textures developed in the two type specimens, as well as the different slip systems activated. At elevated temperatures, the strain rate sensitivity and the activation energy are obtained to characterize the deformation mechanism of the alloy during the temperature range of 423~573K.

Solidification Processing and Fracture Behavior of RuAl-Based Alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Todd Reynolds ◽  
David Johnson
Keyword(s):  
Solid Solution ◽  
Fracture Toughness ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Volume Fraction ◽  
Solidification Processing ◽  
Ductile Phase

ABSTRACTAlloys of RuAl-Ru were processed using various solidification methods, and the fracture behavior was examined. The fracture toughness values for RuAl-hcp(Ru, Mo) and RuAl-hcp(Ru, Cr) alloys ranged from 23 to 38 MPa√m, while the volume fraction of RuAl ranged from 22 to 56 percent. Increasing the volume fraction of RuAl resulted in a decrease in fracture toughness. The hcp solid solution was shown to be the more ductile phase with a fracture toughness approaching 68 MPa?m, while the B2 solid solution (RuAl) was found to have a fracture toughness less than 13 MPa√m. An alloy of Ru-7Al-38Cr (at.%) that consisted of a hcp matrix with RuAl precipitates had the highest room temperature toughness and the greatest hardness.

Development of Tough and Strong Cubic Titanium Trialuminides

2000 ◽  
Vol 646 ◽  
Author(s):  
Robert A. Varin ◽  
Les Zbroniec ◽  
Zhi Gang Wang
Keyword(s):  
Fracture Toughness ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Fold Increase ◽  
Strength Increase ◽  
Solid Solution Strengthening ◽  
Boron Doped ◽  
Temperature Fracture ◽  
Solution Strengthening ◽  
B Doping

ABSTRACTIn this work, the recent breakthroughs in the understanding of the fracture behavior and fracture toughness of L12-ordered titanium trialuminides are described and discussed. First, it is shown that, as opposed to many other intermetallics and specifically those with an L12 crystal structure, the fracture toughness of L12 titanium trialuminides is insensitive to testing in various environments such as air, water, argon, oxygen and vacuum (∼1.3×10–5 Pa). Second, it is reported here that by increasing the concentration of Ti combined with boron (B) doping, the room temperature fracture toughness of a Mn-stabilized titanium trialuminide can be improved by 100% from ∼4 MPam1/2 to ∼8 MPam1/2 and by 150–250% at 1000°C to ∼(10–12) MPam1/2 with a simultaneous suppression of intergranular fracture (IGF) to ∼(40–50%). Almost three fold increase in yield strength to ∼550 MPa is attained at room temperature for high Ti, boron-doped trialuminides. Both Vickers microhardness and strength increase linearly with increasing concentration of (Ti+B) indicating a classical solid solution strengthening response.

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