Sintering stress measurement

X-ray residual stress determination was performed on the surface of the samples prepared by HIP sintering. The measured residual stress was compared with the results calculated by the finite element method (FEM). The electrical resistivity was measured by the four probes method on the slices cut from the cylinder samples. In order to inspect the thermal stability, the samples were annealed at 900 °C for 24 hour in vacuum. The microstructure on the section was observed by scanning electron microscope. 

The technique of loading dilatometry, in which a small, controlled uniaxial stress Pj is applied to a powda- compact during sintering has been used to investigate the simultaneous occurrence of densification and creep, as well as their interaction (57,58). Parameters such as the stress intensity factor < > and the sintering stress 2 can be determined from the data. In the experiments, simultaneous measurement of the time-dependent axial and radial strains allows the determination of the... 

Explain the meaning of the term sintering stress. Briefly describe the methods that can be used to measure the sintering stress, indicating the principles on which each method is based, and the advantages and disadvantages of each method. 

The as-grown cells are usually extremely warped toward the cathode side at room temperature. To reduce the warp, the cells are flattened at 1400°C with a distributed load on the surface. The flattening treatment could reduce the warp at room temperature indicating that the sample is in a plastic state at 1400°C. In contrast, it was reported that the sintering of YSZ does not proceed well below 1250°C [25], Thus, it is considered that the temperature at which both the electrolyte and anode are constrained is between 1250°C to 1400°C. When the temperature at which the electrolyte and anode are constrained is assumed to 1400°C, the calculated residual stress is close to the measured value. 

As FGM interlayer, eleven kinds of sintered compacts in which the mixing ratio of beryllium powder and oxygen free copper powder was different, were manufactured by powder metallurgical method, that is, HP and HIP. In this study, to estimate thermal stress at joining interface, thermal conductivity and thermal expansion coefficient of Be/Cu sintered compacts were measured by laser flash method and laser interferometry method, respectively. The characterization on these compacts was performed by using SEM (Scanning Electron Microscope) to investigate distribution of intermetallic phases on these compacts. 

Based on the measured thermomechanical properties and the microstructure of the graded layer of TiC-NiaAl functionally graded material, using the analysis method, the interface residual thermal stress of TiC-NiyAl sphere in the sintering process was calculated. The relationship between the stress and the content of NiyAl was presented. The results show that the failure mechanics of TiC-NijAl composite may be different in different content of NiyAl. 

SVI should be measured in both machine and transverse directions to determine the extent of isotropy in the tube. If the SVI values are very low (< 1 %) in both directions or equal, the sample is isotropic. This means that the sample has been adequately sintered and stresses have been relieved. If the values are both high, sintering has been poor. If the transverse value is high and the machine direction value is low, then orientation is primarily in the machine direction and it is unbalanced. 

---