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The micromorphology and the concentration o massive precipitates produced by twin-roll casting(TRC processes without and with multi-electromagnetic fields fo Al–Zn–Mg–Cu alloy at 670 °C were investigated in detai by means of optical microscopy(OM) and electron probe micro analyzer(EPMA). The results clearly show tha under a 0.2 T static magnetic field, the macro-segregation bands are remarkably alleviated according to the order o uniform static magnetic field, half-wave oscillating elec tromagnetic field as well as alternating oscillating elec tromagnetic field, as compared with the non-field TRC process(B = 0). Moreover, under the alternating oscillat ing electromagnetic TRC process, almost all segregation bands disappear. Additionally, through the observation on a smaller scale, the netlike precipitates elongated and broken by electromagnetic force, and replaced by numerous bulk depositions. EPMA analysis shows that the added atoms are diffused from deposition to a(Al) matrix, resulting in that the solute concentration in and around the precipitates is tending toward uniformity and stability.
The micromorphology and the concentration of massive precipitates produced by twin-roll casting (TRC processes without and with multi-electromagnetic fields fo Al-Zn-Mg-Cu alloy at 670 ° C were investigated in detai by means of optical microscopy (OM) and electron probe micro analyzer (EPMA). The results clearly show tha under a 0.2 T static magnetic field, the macro-segregation bands are remarkably alleviated according to the order o uniform static magnetic field, half-wave oscillating elec tromagnetic fields as well as alternating oscillating elec tromagnetic field, as compared with the non-field TRC process (B = 0). Moreover, under the alternating oscillatcting electromagnetic TRC process, almost all segregation bands disappear. elongated and broken by electromagnetic force, and replaced by numerous bulk depositions. EPMA analysis shows that the added atoms are diffused from deposition to a (Al) matrix, resulting in that the solute concentration in and around the precipitates is tending toward uniformity and stability.