AL-6XN alloy is metallurgically stable to 1000° F (540° C) and has no phase transformation even after extensive deformation. When exposed to temperatures in the range of 1200-1800° F the opportunity for chi phase formations exists. Chi phase, a chromium-iron-molybdenum compound which is sometimes incorrectly referred to as sigma phase, forms along the grain boundaries depleting the area of molybdenum and chromium reducing the corrosion resistance of the material. In order to help combat chi phase formation, nitrogen was added to the AL-6XN alloy to minimize this formation improving corrosion resistance and increasing strength over a broad range of temperatures, while maintaining the good formability of austenitic stainless steel.
The physical properties of the AL-6XN alloy are similar to those of other austenitic stainless steels (table 1).
Table 1: Comparison of Physical Properties
The elastic modulus values of AL-6XN alloy are lower than those for type 316L stainless steel and Alloy 625. However, these moduli are higher in comparison to such non-ferrous alloys as titanium. The thermal conductivity and coefficient of expansion values are lower than those for type 316L stainless steel but are higher than Alloy 625. Typical physical properties of AL-6XN alloy are presented in table 2.
Table 2: Physical Properties of AL-6XN
Comparative chemistry for AL-6XN alloy vs. 316L stainless steel and other 6% Molybdenum containing products is as follows:
Table 3: Typical Comparative Chemistry
Low copper content gives resistance against chloride corrosion. Cu above 0.75% tends to corrode in high chloride environments. For seawater pitting resistance PREN must be greater than 32.