THE EFFECT OF APPLIED STRESS ON THE DECOMPOSITION OF COPPER-15 NICKEL-8 TIN SPINODAL ALLOYS.

摘要

The effect of applied stress on spinodal decomposition in Cu-15w/oNi-8w/oSn alloys was investigated at various aging temperatures and stress. A diffractometer equipped with a graphite monochromator was built for strong intensities with very low background intensities compared with a conventional diffractometer, which is required for measuring the sidehand of the decomposed structure. A stress-aging technique was developed by employing a high-density infrared radiant heating furnace inside the Instron universal testing machine, which made it possible to heat and quench the specimen extremely fast under applied stress. Good agreement between experiment and theory was obtained regarding the effect of applied stress on the decomposition of the alloys. As the aging temperature approached the critical temperature of 505(DEGREES)C, the anisotropy among the three equivalent composition modulations of the stress aged specimen becomes pronounced. The wavelength of the 001 modulation along the stress axis was smaller than that of the 100 or 010 modulation perpendicular to the stress axis. The growth rate of the modulation along the stress axis was also enhanced due to an applied tensile stress. SAD patterns showed direct evidence of the anisotropy effect of the applied stress to the composition modulation. A theoretical model based on micromechanics concepts was employed to explain the experimental results.