RESIDUAL ELASTIC STRAIN-MEASUREMENT IN HE AT-TREATED SIC WHISKER A2014 COMPOSITE BY NEUTRON-DIFFRACTION

The residual elastic strains in 22 vol.%SiC whisker/A2014 metal matrix composites made by squeeze-casting were examined using a neutron crys tal diffractometer with a one-dimensional position sensitive detector (PSD) and a neutron time-of-flight diffractometer with two-point detec tors (TOF). The ingot of the sample was hot-extruded, then hot-swaged and finally hot-rolled to sheets of 2 mm in thickness. The hot-rolling was performed either parallel (specimen P) or vertical (specimen V) t o the direction of extrusion. The whiskers are aligned with a little s cattering against the extrusion direction in the specimen P, while the ir orientation distribution is nearly two-dimensionally random in spec imen V. The residual stresses were introduced by rapid quenching from 448 K (T6 heat treatment) or 773 K (solution treatment). SiC whisker a nd A2014 alloy were used as the reference materials. It is found that the residual elastic strains in the samples depend upon the orientatio n distribution of the whiskers. The ratio of residual elastic strains in the T6 treated specimen to those in the solution treated one is abo ut 3.0, which is consistent with the ratio of their temperature gaps u pon quenching. The results by PSD and TOF are found almost identical. The residual elastic strains have been calculated on the basis of Eshe lby's equivalent inclusion and Mori-Tanaka's mean field theories. In t he calculation, the S-dimensional orientation distributions of whisker s obtained from the SEM observations on the two mutually orthogonal pl anes of the specimens were taken into consideration. The calculated re sults were in good agreement with the measurements.