Alteration in the Phase Morphology of Ti-6Al-4V Alloy Produced Using Directed Energy Deposition

2020 ◽  
Vol 1000 ◽  
pp. 375-380
Author(s):  
Desrilia Nursyifaulkhair ◽  
Faris Arief Mawardi ◽  
Nokeun Park ◽  
Eung Ryul Baek ◽  
Sungwook Kim
Keyword(s):  
Cooling Rate ◽  
Energy Deposition ◽  
Bottom Layer ◽  
Transformation Products ◽  
Phase Morphology ◽  
Β Phase ◽  
Directed Energy Deposition ◽  
Fast Cooling ◽  
Directed Energy ◽  
Hardness Values

The alteration in phase morphology of Ti-6Al-4V alloy fabricated using directed energy deposition (DED) was investigated in this study. Owing to the fast cooling rate during DED, the specimen exhibited the diffusionless transformation products of martensite (α′) and massive (αm) phases. In the top layer, the α′ exhibited a needle-like morphology with the width of approximately 0.94 μm. Meanwhile, the αm presented a lamellar structure with α thickness of nearly 0.98 μm. In contrast, the morphology of α′ and αm started to decompose into α+β phase in the bottom layer. Furthermore, the hardness values increased with higher deposition layers. These phenomena could be explained by the effect of repetitive heating, as the nature of DED method during the depositing of new layers. Moreover, it was observed the α thickness of αm in the bottom layer was finer than that in the top layer due to the higher cooling rate.

scholarly journals Predicting Microstructure Evolution During Directed Energy Deposition Additive Manufacturing of Ti-6Al-4V

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Cengiz Baykasoglu ◽  
Oncu Akyildiz ◽  
Duygu Candemir ◽  
Qingcheng Yang ◽  
Albert C. To
Keyword(s):  
Microstructure Evolution ◽  
Energy Deposition ◽  
Phase Fraction ◽  
Fe Model ◽  
Metal Powders ◽  
Β Phase ◽  
Α Phase ◽  
Directed Energy Deposition ◽  
Microstructural Model ◽  
Directed Energy

Laser engineering net shaping (LENS) is one of the representative processes of directed energy deposition (DED) in which a moving heat source having high-intensity melts and fuses metal powders together to print parts. The complex and nonuniform thermal gradients during the laser heating and cooling cycles in the LENS process directly affect the microstructural characteristics, and thereby the ultimate mechanical properties of fabricated parts. Therefore, prediction of microstructure evolution during the LENS process is of paramount importance. The objective of this study is to present a thermo-microstructural model for predicting microstructure evolution during the LENS process of Ti-6Al-4V. First, a detailed transient thermal finite element (FE) model is developed and validated for a sample LENS process. Then, a density type microstructural model which enables calculation of the α-phase fractions (i.e., Widmanstätten colony and basketweave α-phase fractions), β-phase fraction, and alpha lath widths during LENS process is developed and coupled to the thermal model. The microstructural algorithm is first verified by comparing the phase fraction results with the results presented in the literature for a given thermal history data. Second, the average lath width values calculated using the model are compared with the experimentally measured counterparts, where a reasonable agreement is achieved in both cases.

scholarly journals Correction to: Characterization and Optimization of Process Parameters for Directed Energy Deposition Powder-Fed Laser System

2021 ◽  
Author(s):  
Daniel Andres Rojas Perilla ◽  
Johan Grass Nuñez ◽  
German Alberto Barragan De Los Rios ◽  
Fabio Edson Mariani ◽  
Reginaldo Teixeira Coelho
Keyword(s):  
Process Parameters ◽  
Energy Deposition ◽  
Laser System ◽  
Directed Energy Deposition ◽  
Optimization Of Process Parameters ◽  
Directed Energy

scholarly journals Hot-Wire Laser-Directed Energy Deposition: Process Characteristics and Benefits of Resistive Pre-Heating of the Feedstock Wire

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 634
Author(s):  
Agnieszka Kisielewicz ◽  
Karthikeyan Thalavai Pandian ◽  
Daniel Sthen ◽  
Petter Hagqvist ◽  
Maria Asuncion Valiente Bermejo ◽  
...  
Keyword(s):  
Heat Input ◽  
Energy Deposition ◽  
Fine Tuning ◽  
Hot Wire ◽  
Process Stability ◽  
Electrical Signals ◽  
Melt Pool ◽  
Directed Energy Deposition ◽  
Directed Energy ◽  
The Stability

This study investigates the influence of resistive pre-heating of the feedstock wire (here called hot-wire) on the stability of laser-directed energy deposition of Duplex stainless steel. Data acquired online during depositions as well as metallographic investigations revealed the process characteristic and its stability window. The online data, such as electrical signals in the pre-heating circuit and images captured from side-view of the process interaction zone gave insight on the metal transfer between the molten wire and the melt pool. The results show that the characteristics of the process, like laser-wire and wire-melt pool interaction, vary depending on the level of the wire pre-heating. In addition, application of two independent energy sources, laser beam and electrical power, allows fine-tuning of the heat input and increases penetration depth, with little influence on the height and width of the beads. This allows for better process stability as well as elimination of lack of fusion defects. Electrical signals measured in the hot-wire circuit indicate the process stability such that the resistive pre-heating can be used for in-process monitoring. The conclusion is that the resistive pre-heating gives additional means for controlling the stability and the heat input of the laser-directed energy deposition.

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