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A new, potentially lower-cost approach for the production of advanced titanium and titanium-alloy materials has been demonstrated using cryogenic technology. The alloys produced have an ultra-fine grained structure, high-angle boundaries, and finely-dispersed particulates having near-nanometer-scale size. These features combine to impart excellent strength levels, good ductility, and excellent microstructural thermal stability. In addition, the powders are macroscopically in the micrometer range having pre-alloying capabilities. This feature allows for easy handling, cleaner surfaces, and no environmental dangers. This paper summarizes the preliminary results of the macrostructures, microstructures, chemistries, and mechanical properties achieved via the cryogenic processing.

This paper presents the results of development efforts relating to an advanced material processing technique, namely cryogenic milling, and its application to the processing of Al-7.5wt%Mg-0.2wt%N-20vol%SiC and Al 8wt%Ti-2wt%Ni nano-composite materials suitable for use in aerospace fastener applications. The effects of cryogenic milling in the material production are investigated via microstructural analysis. The advantages of cryogenic milling in the material production are presented with powder morphology and handling characteristics, and microstructural and nanostructural aspects. The resulting, very homogeneous material is discussed along with resulting mechanical properties, which are obtained through tension tests.

Fastening metallic structure for aerospace applications is relatively straightforward and has been done for some time. Dealing with advanced composites, though, requires a significantly different technological approach, especially primary structure. Although composite material utilization has increased enormously in civil and military aircraft in recent years, the application of composite materials to primary aircraft structure has not kept pace and is still greeted with some skepticism in the aerospace community. In particular, no major transport manufacturer has yet employed composite components for fuselage or wing primary structure. This appears to be changing rather rapidly with the introduction and the evolution of new airframes such as the 7E7 and Blended Wing Body (BWB) concepts.

Aluminum-lithium (Al-Li) alloys have been developed with reduced weight and increased durability characteristics. The application of these new alloys as primary aircraft structure has created the need for refinements in the mechanical joining and stress-coining processes currently employed throughout the aerospace industry. These processes deal specifically with fastener hole preparation, installation processes, and fatigue enhancement techniques associated with stress-coin cold-working methods for mechanical joints. This paper attempts to dispel the myths associated with such processing of 2090 Al-Li alloy sheet and extrusions. Presented are some lessons learned during assembly of the USAF's new C-17A STOL transport airlifter when utilizing Al-Li material.