Solid-State Transformation of an Additive Manufactured Inconel 625 Alloy at 700 °C.

Inconel 625, a nickel-based superalloy, has drawn much attention in the emerging field of additive manufacturing (AM) because of its excellent weldability and resistance to hot cracking. The extreme processing condition of AM often introduces enormous residual stress (hundreds of MPa to GPa) in the as-fabricated parts, which requires stress-relief heat treatment to remove or reduce the internal stresses. Typical residual stress heat treatment for AM Inconel 625, conducted at 800 °C or 870 °C, introduces a substantial precipitation of the δ phase, a deleterious intermetallic phase.

Measurements of melt pool geometry and cooling rates of individual laser traces on IN625 bare plates.

The complex physical nature of the laser powder bed fusion (LPBF) process warrants use of multiphysics computational simulations to predict or design optimal operating parameters or resultant part qualities such as microstructure or defect concentration. Many of these simulations rely on tuning based on characteristics of the laser-induced melt pool, such as the melt pool geometry (length, width, and depth). Additionally, many of numerous interacting variables that make LPBF process so complex can be reduced and controlled by performing simple, single track experiments on bare (no powder) substrates, yet still produce important and applicable physical results.

Side-Chain Protonation States of a Fluorescent Arginine.

An arginine derivative with a fluorescent side-chain, Boc-Arg(Nap)-OH, was prepared by palladium(0)-catalyzed coupling of Boc-Arg-OH with a 4-bromonaphthalimide. The presence of the fluorophore lowers the p of the side-chain guanidinium group by several orders of magnitude, to 9.0 (±0.

Simulation of TTT Curves for Additively Manufactured Inconel 625.

The ability to use common computational thermodynamic and kinetic tools to study the microstructure evolution in Inconel 625 (IN625) manufactured using the additive manufacturing (AM) technique of laser powder-bed fusion is evaluated. Solidification simulations indicate that laser melting and re-melting during printing produce highly segregated interdendritic regions. Precipitation simulations for different degrees of segregation show that the larger the segregation, i.

Phase Fraction and Evolution of Additively Manufactured (AM) 15-5 Stainless Steel and Inconel 625 AM-Bench Artifacts.

A proper understanding of the structure and microstructure of additively manufactured (AM) alloys is essential not only to the prediction and assessment of their material properties, but also to the validation and verification of computer models needed to advance AM technologies. To accelerate AM development, as part of the AM-Bench effort, we conducted rigorous synchrotron-based X-ray scattering and diffraction experiments on two types of AM alloys (AM 15-5 stainless steel and AM Inconel 625). Taking advantage of the high penetration of synchrotron hard X-rays, we determined the phases present in these alloys under different build conditions and their statistically meaningful phase fractions using high-resolution X-ray diffraction.