Dinda, G. P., Dasgupta, A. K., Bhattacharya, S., Natu, H., Dutta, B., and Mazumder, J.
Metallurgical and Materials Transactions A. May 2013, Vol. 44 Issue 5, p2233, 10 p.
Alloys, Rapid prototyping, Transmission electron microscopes, and Computer-aided design
Direct metal deposition (DMD) technology is a laser-aided rapid prototyping method that can be used to fabricate near net shape components from their CAD files. In the present study, a series of Al-Si samples have been deposited by DMD in order to optimize the laser deposition parameters to produce high quality deposit with minimum porosity and maximum deposition rate. This paper presents the microstructural evolution of the as-deposited Al 4047 sample produced with optimized process parameters. Optical, scanning, and transmission electron microscopes have been employed to characterize the microstructure of the deposit. The electron backscattered diffraction method was used to investigate the grain size distribution, grain boundary misorientation, and texture of the deposits. Metallographic investigation revealed that the microstructural morphology strongly varies with the location of the deposit. The layer boundaries consist of equiaxed Si particles distributed in the Al matrix. However, a systematic transition from columnar Al dendrites to equiaxed dendrites has been observed in each layer. The observed variation of the microstructure was correlated with the thermal history and local cooling rate of the melt pool.
Metallurgical and Materials Transactions A. August 2010, Vol. 41 Issue 8, p1917, 11 p.
Crystals -- Structure, Epitaxy, and Rapid prototyping
The texture and crystal orientation of Ti-6Al-4V components, manufactured by shaped metal deposition (SMD), is investigated. SMD is a novel rapid prototyping tungsten inert gas (TIG) welding technique leading to near-net-shape components. This involves sequential layer by layer deposition with repeated partial melting and heat treatment, which results in epitaxial growth of large elongated prior [beta] grains. This leads to a directionally solidified texture, where the prior [beta] grains exhibit only a small misorientation with each other. The [beta] grains grow in 100 direction with a second 100 direction perpendicular to the wall surface. During cooling, the [alpha] phase transformation follows the Burgers orientation relationship leading to a Widmanstatten structure, with orientation relations between most of the [alpha] lamellae and also of the residual [beta] phase. The directionally solidification and the transformation into the [alpha] phase following the Burgers relationship results in a texture, where the hcp pole figures look similar to bcc pole figures.