Low-pressure spray forming of 2024 aluminum alloy

In this paper, a newly developed low-pressure spray forming (LPSF) technique is described, The experimental results obtained with an as-deposited 2024 aluminum alloy are reported. It is shown that the application of reduced pressure significantly decreases porosity as compared to conventionally spray-formed 2024 aluminum alloy, Moreover, the resultant microstructures are similar to those achieved with conventional spray forming. The mechanisms of porosity formation in deposited materials, obtained using both low pressure and conventional spray forming, are discussed. Gas entrapment and interstitial porosity are proposed to be the two major sources of the porosity present in the as-deposited materials. On the basis of the present study, the controlled low-pressure environment during LPSF appears to influence the droplet trajectories and the gas flow field, leading to flow-straightening effects which result in significant reduction of porosity in the deposited materials. (C) 1998 Elsevier Science S.A.