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.

Example of chromium carbides formed along the grain boundaries depleting the surrounding areas of chromium and molybdenum

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

Alloy	Elastic Modulus		Thermal Conductivity at 212° F		Expansion Coefficient from 77 to 212° F
	psi x 106	MPa	Btu-ft/hr-ft2-°F	W/mK	10-6/°F	10-6/°C
Type 316L	29.0	200	9.2	16.0	8.5	17.3
C-276	29.8	205	6.4	9.9	6.2	11.2
C-22	29.9	206	6.5	10.2	6.9	12.4
Titanium	15.0	103	9.5	16.4	5.0	9.1
Alloy 904L	28.3	195	7.6	13.2	8.3	15.0
AL-6XN	28.3	195	6.8	11.8	8.5	15.3
Alloy 625	29.7	205	6.2	10.7	7.1	12.8
Nickel 200	30.0	207	38.8	67.1	7.4	13.4

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

Property	Value	Units
Density	0.291 8.06	lb/in3 g/cm3
Modulus of Elasticity	28.3 x 106 195	psi GPa
Melting Range	2410 to 2550 1320 to 1400	°F °C
Thermal Conductivity 68 to 212 °F 20 to 100 °C	6.8 11.8	Btu/hr · ft · °F W/mK
Coefficient of Expansion 68 to 212 °F 20 to 100 °C	8.5 15.3	10-6/ °F 10-6/ °C
Specific Heat Capacity	0.11 500	Btu/lb·°F J/kg·K
Electrical Resistivity	535 0.89	Ohm·circ mil/ft µΩm
Magnetic Permeability Fully annealed 0.5" plate 65% cold-worked plate	1.0028 1.0028	Oersted (µ at 200H)
Sealing Temperature	1885 1030	°F °C

Comparative chemistry for AL-6XN alloy vs. 316L stainless steel and other 6% Molybdenum containing products is as follows:

Table 3: Typical Comparative Chemistry

	Chromium	Nickel	Molybdenum	Nitrogen	Copper	PREN
AL-6XN	20%	24%	6.3%	0.22%	0.25-0.75%	44.3
316L	16%	10%	2%	0.05%	0.40%	23.4
254 SMO®	20%	18%	6.3%	0.20%	0.80%	44.0
25-6 MO®	20%	25%	6.5%	0.20%	1.20%	44.7
1925 hMO®	20%	25%	6.5%	0.18%	0.90%	44.3

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.