Structures and Properties of a Modified 7075 Aluminum Alloy Produced by Liquid Dynamic Compaction

摘要

A modified 7075 aluminum alloy containing 1 wt %Ni and 0.8 wt %Zr was deposited by the Liquid Dynamic Compaction (LDC) Process and processed by several techniques to full density. The effect of the principal parameters of LDC, namely atomization gas pressure, metal pre-heat temperature, and substrate to nozzle distance, was investigated. Densities of the as-deposited material reached 95 percent. The deposited alloys were fully densified at 400 C (673 K), generally by as little as a 6:1 reduction of area by hot extrusion, though higher reduction were generally used for purposes of structure control as well. No variation in hardness through a 30 mm thick section of an as-deposited preform was found. Gas porosity was of micron size and well distributed. A fine, as-deposited, structure of grain size about 15 to 20 micrometer was observed, associated with a cooling rate during solidification of about 1000 K/s. The grains were equiaxed and uniform in size and no evidence of prior particle boundaries was found. TEM, SEM and chemical analyses indicated a low oxide content, chemical analysis giving an oxygen content 100 ppm for the extruded and heat treated LDC alloy.