The Effect of Sample Preparation upon the Fracture Toughness of Microsized TiAl

2005 ◽  
Vol 297-300 ◽  
pp. 2416-2422 ◽  
Author(s):  
T.P. Halford ◽  
D. Rudinal ◽  
Kazuki Takashima ◽  
Yakichi Higo
Keyword(s):  
Fracture Toughness ◽  
Tial Alloy ◽  
Microelectromechanical Systems ◽  
Elevated Temperatures ◽  
Mems Devices ◽  
Testing Methods ◽  
Preparation Methods ◽  
Micro Scale ◽  
Lamellar Orientation ◽  
Toughness Testing

The effective fracture toughness testing of materials intended for application in MicroElectroMechanical Systems (MEMS) devices is required in order to improve understanding of how they may be expected to perform upon the micro scale. γ-TiAl based materials are being considered for application in MEMS devices required to operate at elevated temperatures. The effect of different preparation methods upon resulting fracture toughness and development of testing methods for these devices is therefore of importance. Micro-sized cantilevers of the γ-TiAl alloy “Alloy 7” (Ti-46Al-5Nb-1W) were therefore prepared using either mechanical or chemical final stage polishing and subsequently used to evaluate fracture toughness. The effectiveness of the evaluation of micro-sized samples of γ-TiAl in this manner is considered, as well as the effects of the different processing methods and variations in properties according to lamellar orientation.

Wafer-Level Strength and Fracture Toughness Testing of Surface-Micromachined MEMS Devices

1999 ◽  
Vol 605 ◽  
Author(s):  
H. Kahn ◽  
N. Tayebi ◽  
R. Ballarini ◽  
R.L. Mullen ◽  
A.H. Heuer
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Microelectromechanical Systems ◽  
Reliability Prediction ◽  
Bend Strength ◽  
Mems Devices ◽  
Wafer Level ◽  
Toughness Testing ◽  
Loading Devices

AbstractDetermination of the mechanical properties of MEMS (microelectromechanical systems) materials is necessary for accurate device design and reliability prediction. This is most unambiguously performed using MEMS-fabricated test specimens and MEMS loading devices. We describe here a wafer-level technique for measuring the bend strength, fracture toughness, and tensile strength of MEMS materials. The bend strengths of surface-micromachined polysilicon, amorphous silicon, and polycrystalline 3C SiC are 5.1±1.0, 10.1±2.0, and 9.0±1.0 GPa, respectively. The fracture toughness of undoped and P-doped polysilicon is 1.2±0.2 MPa√m, and the tensile strength of polycrystalline 3C SiC is 3.2±1.2 GPa. These results include the first report of the mechanical strength of micromachined polycrystalline 3C SiC.

The Fracture Toughness of Polysilicon Microdevices

1998 ◽  
Vol 518 ◽  
Author(s):  
R. Ballarini ◽  
R.L. Mullen ◽  
H. Kahn ◽  
A.H. Heuer
Keyword(s):  
Fracture Toughness ◽  
Microelectromechanical Systems ◽  
Maximum Tensile Stress ◽  
Monotonic Loading ◽  
Modulus Of Rupture ◽  
External Loading ◽  
Mems Devices ◽  
Average Maximum ◽  
Average Modulus ◽  
On Chip

AbstractThe development of polysilicon fracture mechanics specimens with characteristic dimensions comparable to those of typical microelectromechanical systems (MEMS) devices is presented. The notched cantilever specimens are fully integrated with a simultaneously microfabricated electrostatic actuator, which allows on-chip testing of the specimens without the need of an external loading device, and without any possible influences from external sources. Under monotonic loading, the average maximum tensile stress (strength) and average nominal fracture toughness were measured as 4.2 GPa and 3.5 MPa-m½ for boron-doped specimens, and 5.0 GPa and 4.0 MPa-m½ for undoped specimens. An average modulus of rupture of 3.3 GPa and average nominal toughness of 2.7 MPa-m½ were measured for specimens cracked under cyclic resonance loading. The differences between the monotonic loading and cyclic loading data are attributed to fatigue initiation of a sharp crack from the 1 ýtm radius notch. The experimental data is consistent with a critical flaw size in the fabricated devices, a, that is related to the fracture toughness Klc by Klc/a1/2=4600 MPa.

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