Up to now, to our best knowledge, the behavioral characteristics of metals in electroplastic state have not been fully exploited
in friction welding process. NNSFC (National Natural Science Foundation of China) approved (Approval No. 50005017) our application for research support and has supported us since 2000 to establish, as one of several important objectives, the physical model for friction welding process of aluminum alloy under electric field. Section 2 establishes in some detail the
kinetic recrystallization model of the friction welding process in external electric field. Subsection 2.1 establishes the relationship, eq. (4), among the initial heat deformation parameters--temperature, stress, and rotation speed--during the initial recrystallization stage. Subsection 2.2 establishes the relationship, eq.(9), among temperature, stress, and strain rate in the quasi steady friction welding stage in external electric field. Section 3 gives experimental results and analyses. Subsection 3.1 points out that the critical flow stress in the initial dynamic recrystallization stage decreases with increasing interface temperature, increasing electric field intensity, and decreasing rotation speed. Subsection 3.2 points out that: (1) the
strain rate sensitivity exponent in the quasi steady friction welding stage increases with increasing electric field intensity at low electric field intensity but decreases gradually with increasing electric field intensity when the electric field intensity exceeds 522V/mm (Fig.2); (2) the apparent activiation energy of the weld metal in the quasi steady friction welding stage decreases with increasing electric field intensity (Fig.3). Table 2 gives the specific forms of eqs.(4) and (9) for Chinese aluminum alloy LY12CZ (approximately equivalent to ASTM 2024 ) for four values of external electric field intensity: 0, 261 V/mm,522 V/mm,783 V/mm.