Rapid prototyping of 4043 Al-alloy parts by VP-GTAW

This paper presents an investigation on the microstructure and property of 4043 Al-alloy parts built using a novel layer-deposition technique based on a variable polarity gas tungsten arc welding (VP-GTAW) process. Processing parameters strongly affect the geometry, microstructures, roughness, and hardness of a deposited part. A hollow cylindrical part with 120 layers is built up with a good surface quality. The deposited layers have a fine dendrite structure at the top layer, and coarse columnar/cellulargrain structures in the middle and at the bottom of a deposited wall. The deposited wall has some fine equiaxed grains at the surface layers of the sidewalls. The precipitates are primarily distributed at the interdendrite regions and grain boundaries. The bonding zone exhibits an epitaxial and columnar grain growth from the original grains of a Substrate. Precipitates are mainly located at the interior of columnar grains in the bonding zone. The deposited wall exhibits slight increasing trend in hardness from the bottom and middle layers to the top layer. The surface roughness resulting from the fine interlayer striations is found to be in the order of 5 mum, while the verticality of sidewalls mainly depending on the surface ripples is less than 5%. (C) 2004 Elsevier B.V. All rights reserved.