The mechanical behavior and microstructural evolution during high temperature tensile deformation of recrystallizedNi3Al polycrystals doped with boron were investigated as functions of initial grain size, tensile strain rate and temperature. Inorder to obtain more precise information on the deformation mechanism, tensile specimens were rapidly quenched immediatelyafter deformation at a cooling rate of more than 2000Ks−1, and were then observed by transmission electron microscopy (TEM).Mechanical tests in the range of 923K to 1012K were carried out in a vacuum of less than 3×10−4 Pa using an Instron-typemachine with various but constant cross head speeds corresponding to the initial strain rates from 1.0×10−4 to 3.1×10−5s−1.After heating to deformation temperature, the specimen was kept for more than 1.8ks before testing. The following results wereobtained: (1) Flow behavior was affected by initial strain size; with decreasing initial grain size, the level of a stress peak inthe true stress-true strain curve decreased, the steady state region was enlarged and elongation increased. (2) On the basis ofTEM observation of rapidly quenched specimens, it was confirmed that dynamic recrystallization certainly occurred ondeformation of fine-grained (3.3µm) and intermediate-grained (5.0µm) specimens at an initial strain rate of 3.1×10−5s−1 andat 973K. (3) There were some dislocation-free grains among the new recrystallized grains. The obtained results suggest thatboth dynamic recrystallization and grain boundary sliding are operative during high temperature deformation.

• Oh, Chang-Sup
• Han, Chang-Suk | Han, Chang-Suk