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One-Minute Mentor: AerMet Alloys
April 16, 2018
Source: ASM International
The graph shows a comparison of AerMet alloys and maraging steels in terms of (a) ductility vs. specific strength and (b) Charpy V-notch impact toughness vs. specific strength. The family of AerMet alloys provides a good combination of high strength and toughness that makes them attractive for aerospace applications.
Specific strength (ultimate tensile strength/density) compares favorably with maraging steels and titanium alloys. In particular, the gap between ultimate tensile strength and yield strength is indicative of better ductility and toughness for a given specific strength which makes the AerMet alloys very suited to applications that requires high toughness and fatigue tolerance in combination with high strength.
AerMet 100. The AerMet 100 alloy was developed in response to a need from McDonnell Douglas and the U.S. Navy for a stronger and tougher material for the landing gear of the F/A 18 E/F fighter aircraft. The Navy wanted an alloy that could be a drop-in replacement for 300M, but with twice the fracture toughness. The AerMet 100 alloy met the requirements of the Navy with its minimum ultimate tensile strength of 1930 MPa (280 ksi) and minimum fracture toughness of 110 MPa (100 ksi, and as such the “100” in AerMet 100 stands for a fracture toughness of 100 ksi The patent for AerMet 100 specifies double vacuum processing and reduction of impurity elements to extremely low levels. In addition, the presence of silicon and manganese, both of which are present in HY 180 and AF 1410, are reduced to levels less than 0.01 wt%. This alloy is not subject to the same restrictions as AF1410 and thus may be considered a substitute.
Like other carbon-bearing high-strength alloys, heat treatment should take place in a neutral atmosphere furnace, salt bath, or vacuum to prevent decarburization.
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