Creep-rupture properties and grain-boundary sliding in wrought cobalt-base HS-21 alloys at high temperatures

1992 ◽  
Vol 27 (10) ◽  
pp. 2636-2640 ◽  
Author(s):  
M. Tanaka ◽  
H. Iizuka ◽  
F. Ashihara
Keyword(s):  
Grain Boundary ◽  
High Temperatures ◽  
Grain Boundary Sliding ◽  
Creep Rupture ◽  
Boundary Sliding ◽  
Rupture Properties ◽  
Cobalt Base

Simulation of Microcrack Propagation in Creeping Polycrystals Due to Diffusive Grain Boundary Cavitation

1994 ◽  
Vol 47 (1S) ◽  
pp. S122-S131 ◽  
Author(s):  
M. W. D. van der Burg ◽  
E. van der Giessen
Keyword(s):  
Grain Boundary ◽  
Life Time ◽  
Grain Boundary Sliding ◽  
Creep Rupture ◽  
Network Modelling ◽  
Microcrack Propagation ◽  
Polycrystalline Aggregates ◽  
Boundary Sliding ◽  
Creep Deformations ◽  
Excessive Number

Creep rupture in random polycrystalline aggregates is investigated numerically in terms of multi-grain cell studies using a Delaunay network modelling technique. The model involves a representation of the crystalline aggregate by means of special purpose elements attributed to each grain facet. These Delaunay elements account for elastic and creep deformations of the grains, free grain boundary sliding, as well as for the nucleation and diffusive growth of grain boundary cavities until coalescence leads to a facet microcrack. Damage accumulation is simulated numerically, until an excessive number of microcracks cause des-integration of the polycrystal. Primary attention is on the influence of randomness in the microstructure on creep rupture, either in terms of random variations of the size and shape of hexagonal grains, or in terms of random variations in the nucleation properties of grain boundaries. It is found that randomness always tends to decrease the life time. In particular, it is found that the life time depends sensitively on random variations of the geometry of the microstructure.

Creep rupture strength and grain-boundary sliding in austenitic 21 Cr-4Ni-9Mn steels with serrated grain boundaries

1988 ◽  
Vol 23 (2) ◽  
pp. 621-628 ◽  
Author(s):  
Manabu Tanaka ◽  
Ohmi Miyagawa ◽  
Tsuneaki Sakaki ◽  
Hiroshi Iizuka ◽  
Fumio Ashihara ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rupture Strength ◽  
Grain Boundary Sliding ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Boundary Sliding

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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