DETERMINATION OF PRECIPITATE STRENGTH IN ALUMINUM-ALLOY 6056-T6 FROM TRANSMISSION ELECTRON-MICROSCOPY IN-SITU STRAINING DATA

The transmission electron microscopy in-situ straining technique is em ployed to measure the breaking angles of strengthening precipitates in aluminium alloy 6056-T6 as they are sheared by dislocations. The expe rimental determination of the character of bowed dislocation segments when dislocations are pinned on precipitates allows us to calculate th e corresponding line tensions. From this, the maximum forces F-m that precipitates can sustain before being sheared by dislocations are dedu ced. It is suggested that F-m may be regarded as a quantitative parame ter which includes the effects of the various strengthening mechanisms operative in precipitation-hardened alloys. An attempt is made to rel ate the maximum force calculated from in-situ straining data to the ma croscopic yield strength of the material.