Enhanced Aluminum Properties by Means of Precise Droplet Deposition

The use of molten aluminum droplets is investigated for potential application to precision droplet-based net-form manufacturing (PDM). In the proposed application, final structural components are made from the raw stock in one integrated operation by depositing molten metal droplets, layer after layer, via computer information. This work investigates the feasibility of the proposed technology by investigating the issues associated with generating molten aluminum droplets from capillary stream break-up, and examining the mechanical characteristics of the fabricated aluminum components. New results are presented which illustrate the generation of stable streams of molten aluminum droplets at rates of 24,000 droplets/second for a droplet stream speed of 10.9 m/s, corresponding to throughput rates of 2.3 × 10 -4 kg/s (1.85 lb./hour). The droplets travel 2,500 droplet diameters in an inert environment before impingement with the substrate. Microstructural images are completely devoid of splat boundaries, which have been removed by remelting, and the grain size is approximately uniform throughout the field of view of the image that, in most cases presented, contains easily upwards of 30 splats. Also, it has been found that the presence of aluminum oxide in the melt does not influence the average grain size of the component. An oxide barrier however will encapsulate each grain if the oxides are not removed by filtration in the pre-jetting stage. The presence of aluminum oxide in the melt does not prohibit the removal of the splat boundaries. Mechanical analysis shows that fabrication with molten aluminum droplet deposition results in a 30 percent increase in ultimate tensile strength compared to the raw ingot stock.

[1]  Michael J. Cima,et al.  Three Dimensional Printing: Rapid Tooling and Prototypes Directly from a CAD Model , 1992 .

[2]  A. G. Leatham,et al.  The Spray Forming of Superalloys , 1987 .

[3]  David L. Bourell,et al.  Direct Laser Fabrication of a Gas Turbine Engine Component - Microstructure and Properties - Part I , 1998 .

[4]  Lee E. Weiss,et al.  Processing, thermal, and mechanical issues in shape deposition manufacturing , 1995 .

[5]  Cristina H. Amon,et al.  Thermomechanical modeling of molten metal droplet solidification applied to layered manufacturing , 1996 .

[6]  John O. Milewski,et al.  Properties of near-net shape metallic components made by the directed light fabrication process , 1997 .

[7]  Fritz B. Prinz,et al.  Numerical and Experimental Investigation of Interface Bonding Via Substrate Remelting of an Impinging Molten Metal Droplet , 1996 .

[8]  M. Orme,et al.  On the genesis of droplet stream microspeed dispersions , 1991 .

[9]  Brant C. White,et al.  United States patent , 1985 .

[10]  M. Orme,et al.  A novel technique of rapid solidification net- form materials synthesis , 1993 .

[11]  M. Orme,et al.  Phase Change Manipulation for Droplet-Based Solid Freeform Fabrication , 1997 .

[12]  M. L. Griffith,et al.  Multi-Material Processing By Lens , 1997 .

[13]  T. S. Srivatsan,et al.  Rapid solidification processing with specific application to aluminium alloys , 1992 .

[14]  Noshir A. Langrana,et al.  Quality of Parts Processed by Fused Deposition , 1995 .

[15]  E. P. Muntz,et al.  The manipulation of capillary stream breakup using amplitude‐modulated disturbances: A pictorial and quantitative representation , 1990 .

[16]  David L. Bourell,et al.  Direct Selective Laser Sintering and Containerless Hot Isostatic Pressing for High Performance Metal Components , 1997 .

[17]  M. Orme,et al.  PRECISION DROPLET-BASED MANUFACTURING AND MATERIAL SYNTHESIS: FLUID DYNAMICS AND THERMAL CONTROL ISSUES , 1996 .

[18]  R. Merz,et al.  Shape Deposition Manufacturing With Microcasting: Processing, Thermal and Mechanical Issues , 1998 .

[19]  Paul F. Jacobs,et al.  Rapid Prototyping & Manufacturing: Fundamentals of Stereolithography , 1992 .