Fatigue Crack-Growth Resistance of Aluminum Alloys Under Spectrum Loading. Volume 2. Aluminum Lithium Alloys

摘要

The objective of this program is to develop metallurgical guidelines and test methodologies for selection and development of spectrum fatigue-resistant, high-strength aluminum alloys of aircraft structural application. This volume (II) describes the results of characterizations of six experimental alloys containing substantial amounts of lithium. Chemistry, temper, and grain structure were varied to produce systematically controlled microstructures. The six alloys were characterized for chemically composition, microstructure, tensile properties, and fracture toughness. Fatigue crack propagation (FCP) tests were conducted on specimens of each alloy for both constant-amplitude loading and two F-18 load spectrums. One of the spectrums was dominated by tension loads (TD) and the other spectrum contained tension and compression loads (TC) of nearly equal magnitude. The spectrum FCP testing was performed at the maximum peak stress of 145 MPa (21 ksi). Pertinent fracture surface features were documented on the spectrum fatigue specimens.