| 摘要 |
The invention provides an aluminum alloy substrate used for magnetic discs, and a method of manufacturing the same. Even if an aluminum alloy substrate is heated to be as high as 500 DEG C, worsening of smoothness and thickening of crystalline grains are prevented. The aluminum alloy substrate comprises 3.5% to 6% by mass of Mg, balance being Al and unavoidable impurities. The variable quantity of the smoothness of the aluminum alloy substrate before and after heating within 10 seconds at a tempetature of 500 DEG C is below 5um, and the variable quantity of the average grain diameter of the aluminum alloy substrate before and after heating within 10 seconds at a tempetature of 500 DEG C is below 10um. According to the method of manufacturing the aluminum alloy substrate used for magnetic discs, pack annealing of the aluminum alloy substrate used for magnetic discs includes the steps of holding the substrate for more than two hours at a temperature of more than 350 DEG C under a condition that the temperature rises into over 350 DEG C at a speed of 2 DEG C per minute, and cooling at a cooling speed of below 2 DEG C per minute.
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