Time dependence of gamma gamma lattice mismatch in creep deformed single crystal superalloy SC16 at 1173 K

The profiles of 001 and 002 reflections have been measured at 1173 K as a function of time by means of X ray diffraction XRD on tensile creep deformed specimens of single crystal superalloy SC16. Decrease in line width full width at half maximum FWHM by about 7 and increase in peak position by about 3x10 4 degrees was detected after 8.5x104 s. Broadening of the 002 peak profile indicated a more negative value of the lattice misfit after the same time period. The results are discussed in the context of the anisotropic arrangement of dislocations at the amp; 61543; amp; 61487; amp; 61543; interfaces during creep and their rearrangement during the thermal treatment at 1173

Temperature dependence of x ray intensity profile FWHM of the gamma phase in the creep deformed single crystal superalloy SC16

High resolution diffraction using synchrotron x ray radiation was applied to study amp; 947; precipitates with an L12 superlattice crystal structure in the single crystal superalloy SC16 after creep deformation at 1223 amp; 8201;K with a creep strain of 0.5 for tensile and compressive loads, respectively. The measurements of full width at half maximum FWHM of 001 and 100 amp; 947; superlattice reflections were performed at various temperatures from ambient temperature to 1173 amp; 8201;K in vacuum. The experimental results revealed that the FWHM of both reflections decrease with increasing temperature. It is well known that changes in particle size and lattice distortion in materials could lead to a variation of FWHM. The observed behaviour is discussed in the light of both the above mentioned aspects. The decrease in the peak width is mainly attributed to the temperature dependence of the internal strain stat

Temperature dependence of lattice distortion in strongly creep deformed single crystal superalloy SC16

Specimens of single crystal superalloy SC16 have been pre deformed at 1223 K to strain of 15 under tensile load of 150 MPa. The profiles of the 001 superlattice reflection of the gamma precipitate phase as well as the profiles of the 002 reflections of the fcc matrix phase and of gamma precipitate phase have been measured between RT and 1073 K by means of X ray diffraction XRD . From these measurements the lattice distortion of the gamma precipitates and the lattice misfit between gamma and gamma phase have been determined as a function of temperature. The width of the 001 reflection as well as the lattice misfit decreased as a function of temperature. The results are ascribed to the anisotropic arrangement of dislocations at the gamma gamma interfaces and to the different thermal expansion coefficients of the gamma and gamma phase. A comparison of lattice misfit with previous measurements on moderately strained specimens suggests that the measured changes in lattice structure are predominantly created in stage I of creep deformatio

Lattice distortion in gamma precipitates of single crystal superalloy SC16 under creep deformation

Specimens of single crystal superalloy SC16 were creep deformed at 1223 K along [001] up to 0.5 creep strain using stresses of 150 MPa and 150 MPa, respectively. Line widths and peak positions of superlattice reflections were measured by means of X ray diffraction parallel and perpendicular to the load axis in the temperature range between 293 K and 1173 K. The line widths were found to decrease with the increase of temperature for both directions on the two specimens after tensile and compressive creep deformation. After both kinds of creep deformation the crystal lattice showed tetragonal distortion which decreased with increasing temperature. The tetragonality after tensile creep deformation was larger than unity while it was smaller than unity after compres sive creep deformation. The peak positions and widths restored after cooling back to room tempera ture. The experimental results can qualitatively be explained by the creation of dislocations during deformation and their anisotropic arrangement at the Gamma Gamma Prime interface