Base Metal Microstructure Considerations For Aluminum Finishing

摘要

Aluminum components tested and found to be conforming to design specifications may sometimes exhibit finish deficiencies after anodizing in a well controlled process in spite of different lots of conforming material (same alloy and temper) finishing well through the same process. The answer to the problem was found in the overlooked characteristic of microstructure. This paper examines the relationship between temper designations, microstructure, and the precipitation hardening process. Published data and results of a current study will be combined to show that although hardness and chemistry may classify a certain alloy and temper, this data can mask an overaged condition of the aluminum, rendering it not readily processable by standard anodizing. The reactions which occur during aluminum finishing will also be discussed.