YOUNGS MODULUS MEMORY EFFECT DURING THE ANNEALING OF SUBMICROCRYSTALLINE COPPER

The temperature dependence of Young's modulus E(T) in submicrocrystall ine copper has been investigated both on heating and on cooling within a temperature range from 20 to 400-450 degrees C. The copper samples have been subjected to several successive heating-cooling runs with in creasing maximum temperature T-a. At T = T-a the samples were annealed for 2 h. An initial submicrocrystalline structure with a grain size a bout 200 nm has been produced by heavy plastic deformation. An increas e in the modulus during the anneal has been observed. The modulus was measured on rod-shaped samples by a resonance technique at frequencies near 100 kHz. Some of the samples exhibit, after the anneals, a split ting of the resonance curve into several maxima. Moreover, the tempera ture dependences of the additional maxima correspond to the E(T) curve s measured during the previous heating-cooling runs. This memory effec t is discussed.