Computer experiment on superposition of strengthening effects of different particles
Particle-hardening materials, particularly high strength aluminum alloys, usually contain two or more types of second-phase particles. While the strengthening effect of mono-dispersed particles has been studied extensively and hence well formulated, a rational and consolidated evaluation of superposed hardening effects of different particle mixtures is still an open problem both experimentally and theoretically. A computer simulation technique is utilized to examine the details of the problem. The technique developed is based on the circle-rolling approach of Morris et al. The strengthening stress {tau}{sub p} due to the mixture of different particles is determined by examination of a dislocation-slip process through the particles on one slip plane and along one slip direction under the action of an applied shear stress {tau}. Two kinds of particle mixtures are investigated. One consists of hard or unshearable point-like particles and soft or shearable point-like ones. The other is a mixture of two types of unshearable plate-like particles. The simulation results indicate that the superposition law can be well described by an equation {tau}{sup {alpha}} = n{sub {Alpha}}{sup {alpha}/2}{tau}{sub {Alpha}}{sup {alpha}} + n{sub {Beta}}{sup {alpha}/2}{tau}{sub {Beta}}{sup {alpha}} where n{sub {Alpha}} and n{sub {Beta}} are the density fractions of {Alpha}- and {Beta}-particles, {tau}{sup {Alpha}} and {tau}{sub {Beta}} the strengthening stresses due to pure {Alpha}- and {Beta}-particles, and the exponent {alpha} varies between 1.0 and 2.0. Application to the spherical precipitates predicts that a bi-modal particle size distribution can give rise to about an 8% increment in strengthening stress with regard to a single size distribution that is normally produced by conventional aging. Calculated values using the simulation method compare favorably with those determined experimentally.
- OSTI ID:
- 353465
- Journal Information:
- Acta Materialia, Vol. 47, Issue 6; Other Information: PBD: 23 Apr 1999
- Country of Publication:
- United States
- Language:
- English
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