Statistically significant, room temperature, age strengthening has been observed in 23 of 25 separate studies conducted in nine different foundries. The increase in strength ranged from 3.3 percent to a high of 13.5 percent. The shape of the aging curve with time is logarithmic with most of the aging occurring during the first ten days of storage. The strength increase is time and temperature dependent and can be accelerated by holding the test bars at temperatures in the range of 185 deg F (70C) to 545 deg F (233C) prior to testing.
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