Considers efforts to date to produce parts by direct selective laser sintering (SLS) of metals, including post processing to improve structural integrity and/or to induce a transformation. Provides a brief overview of the basic principles of SLS machine operation, and discusses materials issues affecting direct SLS of metals and the resultant properties and microstructures of the parts. Reviews results of past efforts on SLS of metal systems such as Cu‐Sn, Cu‐Solder (Pb‐Sn), Ni‐Sn, pre‐alloyed bronze (Cu‐Sn). Finally discusses more recent efforts on SLS of bronze‐nickel powder mixtures in greater detail.

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nologies are commercially available to produce complexly shaped, three-dimensional (3-D) parts and tooling in a wide range of materials, including paper, polymers, wax, sand, ceramics, and metals.The next major advance in SFF research and development is taking place in the area of direct fabrication processes, especially for the low-volume production of functional metal, cermet, and ceramic components or tooling. Direct fabrication implies layerwise shaping and Editor's Note: A hypertext-enhanced version of this paper can be found on JOM's web site at www.tms.org/pubs/ journals/JOM/9812/Das-9812.html.Selective laser sintering/hot isostatic pressing is a hybrid direct laser fabrication method that combines the strengths of both processes. Selective laser sintering can produce complexly shaped metal components with an integral, gas-impermeable skin. These components can then be directly post-processed to full density by containerless hot isostatic pressing. The use of the hybrid fabrication method, envisioned as a rapid, low-cost replacement for conventional metalcan hot isostatic pressing, is currently being studied for alloy 625 and Ti-6Al-4V alloys. The microstructure and mechanical properties of selective-laser-sintering processed and hot isostatically pressed post-processed material compare well with those of conventionally processed material.

SYNOPSISLow molecular weight poly (methylmethacrylate) and poly (methylmethacrylate-co-n-butylmethacrylate) emulsion-based polymers are developed for use as fugitive binders of high temperature powders to be used with the rapid prototyping method known as selective laser sintering. Kinetics of the homopolymerization of methylmethacrylate and n-butylmethacrylate are found to deviate from Smith-Ewart Type I1 predictions. Reactivity ratios for the monomer pair are determined and indicate the pair to yield random copolymers. Molecular weight was controlled by the addition of chain transfer agents. Several transfer agents were studied and one, Iso-octyl-3-mercaptopropionate, was selected for use with emulsion polymerizations. Glass transition temperatures of the homopolymers and copolymers were studied.