| Two distinct but closely related investigations were conducted to determine influence of spray deposition processing on Al-Cu-Mg-Ag alloys. Initially, the influence of alloying elements on the microstructure and mechanical properties of four spray deposited Al-Cu-Mg-Ag alloys was investigated, in order to better understand the microstructural evolution and to obtain preliminary information regarding the mechanical behavior of spray deposited Al-Cu-Mg-Ag alloys. Transmission electron microscopy (TEM) revealed the presence of for Ag-containing alloys and Al-Cu-Mn dispersoids for Mn-containing alloys. Tensile tests on each of the alloys in the peak-aged and over-aged (1000 hours at 160°C) conditions were performed at both room and elevated temperatures. These tests revealed that the peak-aged alloys exhibited relatively high stability up to 160°C, with greater reductions in strength being observed at 200°C, especially for the high Mn, low Cu/Mg ratio (6.7) alloy. The greatest stability of tensile strength following extended exposure at 160°C was exhibited by the high Cu/Mg ratio (14), Ag-containing alloy, which revealed reductions in yield strength of about 2.5%, with respect to the peak-aged condition, for the alloys tested at both room temperature and 160°C. Based on the results of the preliminary studies, a single Al-Cu-Mg-Ag alloy (C415) was chosen for the main investigation, whose objective was to determine the direct influence of spray deposition processing on the microstructure and mechanical properties of the alloy by performing a direct comparison between spray deposited and homogenized ingot materials. To that end, spray deposited and homogenized ingot C415 were identically processed, characterized, and tested to determine room temperature fracture toughness, hardness and fatigue, room and elevated temperature tensile and creep strength. Both alloys exhibited , , and several dispersoid phases within the matrix as well as and fine precipitate free zones at the grain boundaries. Spray deposition processing resulted in comparable (although slightly reduced) hardness, tensile, fatigue and creep strength and significantly improved fracture toughness (32% increase in the short transverse direction) and room temperature ductility, compared with the homogenized ingot material. The relationship between alloy microstructure and the resulting mechanical behavior of spray deposited and homogenized ingot C415 is discussed in detail. |
