Particle-size-distribution effects in precipitation hardening. Third annual progress report, February 1, 1971-December 31, 1971
Technical Report
·
OSTI ID:6422644
Theoretical work on the diffusion-controlled coarsening of spherical precipitates, grain-boundary precipitates, and fibers in unidirectionally solidified eutectics was completed. Several theoretical problems involving nearest neighbor particle spacings were solved and a unified method for describing the theoretical cumulative distribution functions associated with the three coarsening processes was developed. Experimental data on the coarsening of ..gamma..' precipitates in aged Ni-Cr-Al alloys show that there is no effect of volume fraction on the ..gamma..' coarsening kinetics, in contradiction to our earlier work on these same alloys. The new results are a consequence of improved statistical measurements and computer processing of the raw data. The initial observations on ..gamma..' coarsening in bimodal distributions are described. It is shown that a minimum ..gamma..' coarsening in bimodal distributions are described. It is shown that a minimum ..gamma..' particle spacing for the class I precipitates (which form on aging at 800/sup 0/C) is necessary in order for class II ..gamma..' precipitates (which form on reaging at 600/sup 0/C) to exist. For small spacings the ..gamma..' particle size distributions remain unimodal. Reasons for this behavior are discussed. Results on sinusoidal aging of ..gamma../..gamma..' alloys show that sinusoidal aging accelerates the growth rate of the average ..gamma..' particle. The influence of amplitude and frequency is described.
- Research Organization:
- California Univ., Los Angeles (USA). School of Engineering and Applied Science
- DOE Contract Number:
- AT03-76ER70172
- OSTI ID:
- 6422644
- Report Number(s):
- UCLA-ENG-7214; UCLA-34P172-7
- Country of Publication:
- United States
- Language:
- English
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