The Influence of Second Particals on Grain Boundary Sliding

2014 ◽  
Vol 988 ◽  
pp. 49-55
Author(s):  
Jian Qiang Zhang ◽  
Jun Zhang ◽  
Guo Sen Zhu ◽  
Yan Jun Zheng ◽  
Shao Wei Li ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Boundary ◽  
Slow Rate ◽  
Secondary Electron ◽  
Ambient Pressure ◽  
Grain Boundary Sliding ◽  
Nucleation Sites ◽  
Second Phases ◽  
Boundary Sliding ◽  
Boundary Deformation

The effect of second particles on the grain boundary deformation in 304 type austenitic stainless steel was studied. Flat tensile samples with marker scratches on the surface were strained at slow rate at intermediate temperatures (300-500 °C) at ambient pressure. It seems that the sensitized material decreased creep rate and needed more stress to generate deformation of grain boundary, suggesting Cr carbides decreased the grain boundary sliding. Thus, the resistance to SCC crack propagation could be improved. The Charpy tests suggested that sensitized material had lower fracture toughness; this was due to the GB carbides that acted as nucleation sites for brittle fracture. Characterizations of the tensile samples were carried out using a secondary electron microscope in order to understand whether second phases can affect the creep behavior and grain boundary sliding.

The Effect of Precipitated Phases on Creep Behavior

2014 ◽  
Vol 703 ◽  
pp. 363-369
Author(s):  
Jian Qiang Zhang ◽  
Yan Jun Zheng ◽  
Li Wang ◽  
Shao Wei Li ◽  
Jing Xu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Creep Rate ◽  
Grain Boundary ◽  
Creep Behavior ◽  
Slow Rate ◽  
Grain Boundary Sliding ◽  
Second Phases ◽  
Boundary Sliding ◽  
Precipitated Phases

The effect of precipitated phases on the creep in 300s type austenitic stainless steel used in auto-tailpipe was studied. Flat tensile samples with marker scratches on the surface were strained at slow rate at 400°C. It show that the sensitized material decreased creep rate and needed more stress to generate deformation of grain boundary, suggesting Cr carbides decreased the grain boundary sliding. Thus, the resistance to SCC crack propagation could be improved. Characterizations of the tensile samples were carried out using a SEM in order to understand whether second phases can affect the creep behavior and grain boundary moving.

Fracture Toughness and Internal Friction of GlidCop®Al-25 Alloy

1998 ◽  
Vol 540 ◽  
Author(s):  
S. Tähtinen ◽  
M. Pyykkönen ◽  
S. Smuk ◽  
H. Hänninen ◽  
Y. Jagodzinski ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Boundary Interaction ◽  
Two Component ◽  
Temperature Component ◽  
Boundary Sliding ◽  
Increasing Temperature ◽  
Friction Study

AbstractFracture toughness was found to decrease rapidly with increasing temperature in dispersionstrengthened GlidCop®Al-25 copper alloy both in the as-supplied condition and neutron irradiated to a dose of 0.3 dpa. Internal friction study revealed two-component peak. Grain-boundary sliding was recognized to be responsible for the low-temperature component of the peak, which disappears after irradiation and restores after the heating above 900 K. This points out that the changes in the particle — grain boundary interaction, apparently, due to the defects at the interfaces produced by irradiation are responsible for the drop of fracture toughness in A125 alloy.

Influence of Second Phases on the Superplasticity of Mg-Tm-Y-CeMM Alloys Containing LPSO-Phases

2016 ◽  
Vol 879 ◽  
pp. 1477-1482
Author(s):  
Pablo Pérez Zubiaur ◽  
Judith Medina ◽  
Gerardo Garcés ◽  
Paloma Adeva
Keyword(s):  
Grain Boundary ◽  
Earth Element ◽  
Volume Fraction ◽  
Grain Boundary Sliding ◽  
Metal Alloys ◽  
Lpso Phase ◽  
Transition Metal Alloys ◽  
Sliding Mechanism ◽  
Second Phases ◽  
Boundary Sliding

The effect of the nature of the second phases in extruded Mg-TM-Y-CeMM (TM refers to a transition metal) alloys reinforced by intermetallic MgRE (RE refers to a rare earth element) compounds and LPSO-phase on their superplasticity has been evaluated between 300 and 400°C at the strain rate of 10-4 s-1. The data have been compared with those of alloys containing a similar volume fraction of the LPSO-phase. The results evidence that no superplasticity below 350°C was found in the alloys containing exclusively the LPSO-phase while the alloys containing both MgRE compounds and LPSO-phase deform superplastically by grain boundary sliding from 300°C. These differences are related to the different behaviour of MgRE compounds and LPSO-phase in the course of superplastic regime. MgRE compounds assist to accommodate the deformation more easily than LPSO-phase, reducing tendency to develop cavities and extending the time for the occurrence of necking. The size and volume fraction of the respective phases are critical in order to promote enhanced superplastic behaviour. Maximum elongations are attained in the alloys combining similar volume fractions of MgRE compounds and LPSO-phase in which their size is reduced to the maximum. An increase in the particle size of the second phases, especially in the case of the LPSO-phase, hinders the grain boundary sliding mechanism in the alloys.

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.

INTERNAL FRICTION PEAKS CONNECTED WITH GRAIN BOUNDARY SLIDING IN Al

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-759-C9-764
Author(s):  
E. Bonetti ◽  
A. Cavallini ◽  
E. Evangelista ◽  
P. Gondi
Keyword(s):  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Boundary Sliding
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