Laser Spray Fabrication for Net-Shape Rapid Product Realization LDRD

et al. 2009

In this article, the laser-engineered net shaping (LENS) process is implemented to fabricate netshaped Fe-based Fe-B-Cr-C-Mn-Mo-W-Zr metallic glass (MG) components. The glass-forming ability (GFA), glass transition, crystallization behavior, and mechanical properties of the glassy alloy are analyzed to provide fundamental insights into the underlying physical mechanisms. The microstructures of various LENS-processed component geometries are characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The results reveal that the as-processed microstructure consists of nanocrystalline a-Fe particles embedded in an amorphous matrix. An amorphous microstructure is observed in deposited layers that are located near the substrate. From a microstructure standpoint, the fraction of crystalline phases increases with the increasing number of deposited layers, effectively resulting in the formation of a functionally graded microstructure with in-situ-precipitated particles in an MG matrix. The microhardness of LENS-processed Fe-based MG components has a high value of 9.52 GPa.

Section: Introductionmentioning

confidence: 99%

Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping

et al. 2009

“…[1,2] LENS materials processing uses the high power density provided by the laser beam, which is focused on the deposited components, as shown in Figure 1. As a result, the built material experiences heating, melting, possible vaporization, and resolidification, so that it is considered as a thermal process.…”

Section: Introductionmentioning

confidence: 99%

Thermal Behavior and Microstructural Evolution during Laser Deposition with Laser-Engineered Net Shaping: Part I. Numerical Calculations

et al. 2008

212

Laser-engineered net shaping (LENS) is a rapid direct manufacturing process. The LENS process can be analyzed as a sequence of discrete events, given that it is a layer-by-layer process. The thermal history associated with the LENS process involves numerous reheating cycles. In this article, the thermal behavior during laser deposition with LENS is simulated numerically by using the alternate-direction explicit (ADE) finite difference method (FDM). The simulation results showed that deposited material experiences a significant rapid quenching effect during the initial stages of deposition and can attain a very high cooling rate. With an increase in deposit thickness, the rapid quenching effect decreases and eventually disappears. The effects of the processing parameters on the thermal behavior of deposited materials were also simulated and analyzed. The objective of this study is to provide insight into the thermal history during the LENS process, where the ability to correlate process parameters to microstructural evolution is a motivating force.

“…[27,33] Therefore, the thermal stress between the TiC particles and matrix can reach approximately 332 MPa when cooled to room temperature. Furthermore, due to the layer additive nature of the LENS processing, the thermal behavior associated with LENS processing involves multiple reheating cycles, [15,16] leading to thermal stress cycles, which could also cause the generation of dislocations in Ti6Al4V matrix. The precipitate Ti-Ni particles were small with size about 300 nm and close to round in shape, which is less likely to initiate a crack or to act as a notch.…”

Section: Microstructure and Analysismentioning

confidence: 99%

“…[13,14] The LENS process is a laserassisted, direct metal manufacturing process originally developed at Sandia National Laboratories. [15] The LENS process incorporates features from stereo-lithography and laser cladding, using computer-aided design (CAD) file to control the forming process. Powder is delivered in a gas stream through four nozzles that converge at the same point on the focused Nd:YAG laser beam to form a molten pool, and a threedimensional part can be generated line-by-line and layer-by-layer via additive processing.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Properties of Laser-Deposited Ti6Al4V Metal Matrix Composites Using Ni-Coated Powder

et al. 2008

As a layer additive rapid manufacturing process, laser engineered net shaping (LENS) can fabricate three-dimensional components directly from a computer-aided design (CAD) model. In this work, the LENS process was employed to fabricate Ti6Al4V metal matrix composites using powder mixtures of gas-atomized Ti6Al4V powder and varying volume fractions of Ni nanocoated TiC particles. The as-fabricated microstructures were studied using scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), differential thermal analyzer (DTA), and transmission electron microscopy (TEM) techniques. The interfaces between the metal matrix and ceramic particles were examined. The presence of intermetallic phases and resolidified TiC particles was rationalized on the basis of the thermal field during deposition. The influence of LENS parameters on the microstructure evolution and mechanical behavior of the metal matrix composites (MMCs) was also discussed.