Research

Students: Mohammadreza Asherloo, Melody Delpazir

In this project, irregular Ti-6Al-4V powders produced by hydride-dihydride process with two particle size distributions of fine (bimodal) and coarse (monomodal) are LB-PBF processed. A wide variety of process parameters including laser power, scan speed, and hatch space are used to map processing window for these non-standard powder. Porosity characterization reveals that the shape and probability distribution of pores rely on hatch spacing and melt pool size in which a relative density of 99.94% is achievable with decreased hatch spacing and increased melt pool size. Mechanical behavior such as tensile strength and fatigue life are comparable to those fabricated from spherical Ti-6Al-4V powders.

Student: Mohammad Jamalkhani Khameneh, Maciej Dorula

As a non-beam-based AM method, BJ3DP is a process where a liquid binder is jetted on layers of powdered materials, selectively joined and then followed by densification process. Among AM technologies, binder jetting holds distinctive promise due to possibility of rapid production of complex structures to achieve isotropic properties in the 3D printed samples. We aim to understand the role of powder characteristics (e.g. morphology, mean size, and distribution), printing process parameters (e.g. layer thickness, print orientation, binder saturation, print speed, and drying time), sintering (e.g. temperature and holding time) and post-processing on microstructure and mechanical properties and corrosion behavior of 3D printed parts. We also inclined to use structural, biocompatible and functional materials to fabricate end-user 3D printed parts.

Student: Mohammad Jamalkhani Khameneh, Dominick Sossong

Studying densification kinetics via isothermal sintering (e.g., constant temperature and various holding times) is a tedious and time-consuming procedure. In addition, sintering anisotropy of binder jetted parts from ultra-fine and non-spherical powder is a complex subject. These issues will be overcome by using a novel in-situ imaging system.

Student: Mohammadreza Asherloo

Alloy 718 is fabricated by LB-PBF with standard EOS parameters to attain fully dense parts. We aim to investigate the role of hot isostatic pressing on the microstructural evolution at the horizontal and vertical directions compare to the as-built alloy 718. The as-build LB-PBF alloy 718 shows heterogeneous columnar grains with inter-dendritic micro-segregation; while, post-heat treatments alter grain structure by formation of recrystallized grains with carbide precipitates. Grain morphology and phase formation are characterized by scanning electron microscopy in conjunction with electron backscatter diffraction and X-ray diffraction. Hardness mapping is carried out on cross-sections including perpendicular and along the build direction to understand the hardness distribution of different heat treated parts.

Student: Melody Delpazir, Sourabh D. Bagi, Victor Guma

In fusion based AM parts, the microstructural features such as grain size distribution and texture, porosity, inclusions, surface roughness, residual stress, elemental segregation, and phases play an important role on the corrosion behavior. Generally, laser power, scan speed and hatch spacing are influential processing parameters that control manufacturing of defect-free structures. Corrosion behavior of AM parts are different from those fabricated by casting or metal forming due for the microstructural characteristics attained by rapid solidification. We aim to understand correlations of feedstock chemistry, process parameters, post treatment on grain structure, residual stress, defects and their impact on corrosion performance, both electrochemical behavior and high temperature oxidation.