REDUCTION OF AVIATION ALUMINUM PRECIPITATION HARDENING PROCESS TIME

Various types of thermal treatments based on aluminum alloy Precipitation hardening process, are designed to provide alloys different properties depending on its future use. This project will examine the process of artificial Precipitation hardening T6, in purpose to improve the mechanical properties and obtaining maximum strength for aluminum alloy 7075. Project goals where to perform a shortened heat treatment (T6) for aluminum alloy 7075 in variable thicknesses using 2 steps treatment, while maintaining the mechanical properties required by the standard. If the experiment succeed, applying the proposed process to the specification (AMS2770M). According to AMS 2770M, in order to reach the maximum mechanical of 7075 alloy, the precipitation hardening process (T6) should be at temperature of 121^oC for 23-25 hours. Based preliminary trials that were analyzed in JMP statistical, it was discovered that the process time can be reduced by dividing the process into two steps of in different duration and temperature. The first step is 107^oC for 3 hours, and the second is 160^oC for 5 hours. By using the new process, the total process time will be shortened significantly. After determining the statistical sample size, nine different types of Thermal treatment were performed as described above. Furthermore, six different thicknesses tested in the range of 0.050"-0.125". Finally, mechanical properties, electrical conductivity and corrosion resistance were tested (720 samples). All of the test results applied the standard demand. Then, were statistically analyzed and the highest confidence level (99.95%) was received. Hence, we can conclude that this process is a worthy alternative to the existing process. Consequently, application was field to the Engineering Division in the Israel Aerospace Industry to approve the proposed alternative process.

Nizan Ashkenazi and Shachar Levy equally contributed to this abstract.