Aging Aluminum Alloy 7085 Mold Blocks Part 2: Continuous Non

Aging Aluminum Alloy 7085 Mold Blocks Part II: Continuous Non-Isothermal Aging
J.T. Staley, Sr., E. Austin, D.B. Glanton, B. Godin, and G.

The acceptance of alloy 7085 by the polymer injection molding industry led to increased demands on the aging furnaces at Alcoa's Cleveland Works, so they asked us to develop an even shorter aging practice. We explored the feasibility of combining the stage that nucleates GP zones with the stage that transforms them into h' and h precipitate. We determined the heating rate that allowed GP zones to grow continuously at a rate sufficient to prevent reversion as the temperature increased. We also determined that the kinetics of overaging 7085 during continuous aging could be predicted by integrating effects of isothermal overaging. Where:
YS = yield strength
YSmax = constant
dt = differential time
Fys = AYS exp(Q/RT)
AYS = constant
Q = activation energy
R = gas constant
T = absolute temperature

We determined that a linear heating rate of 25°F/hr. produced target strength in 11.25 hours. Heating rate need not be linear. Depending on the size of the load and the characteristics of the furnace, target properties can be obtained by setting the furnace air temperature at 315 F or higher as long as the heating rate below 300 F is sufficiently low.

Publisher: TMS
Product Format: PDF
Pages: 143-150
Date Published: June 1, 2007
Discounted member price: 10.00
25.00
You could save: 60.0%