LPBF Processability of NiTiHf Alloys: Systematic Modeling and Single-Track Studies

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• NiTiHf high-temperature shape memory alloys (HTSMAs) offer potential for extreme environments.
• Limited research exists on their processability using laser powder bed fusion (LPBF).
• Solidification cracking is a primary challenge in LPBF of these alloys.

Purpose of the Study:

• To investigate the printability of NiTiHf alloys with varying Hf content (1, 2, 15, 20 at. %) using LPBF.
• To identify and mitigate solidification cracking during the LPBF process.
• To establish a processability window for NiTiHf HTSMAs.

Main Methods:

• Computational modeling using Thermo-Calc/2022a to calculate solidification cracking susceptibility (Kou's index, Scheil-Gulliver model).
• Experimental validation using a powder-free laser remelting method on NiTiHf ingots.
• Analysis of alloy composition effects on printability.

Main Results:

• Determined solidification cracking susceptibility for different NiTiHf compositions.
• Developed a powder-free laser remelting technique for process validation.
• Established a processability window with no cracking likelihood under various LPBF conditions (laser power, scan speed).

Conclusions:

• The study provides critical insights into the processability of NiTiHf HTSMAs via LPBF.
• Identified key factors influencing solidification cracking.
• The established processability window facilitates the use of these alloys in advanced engineering applications.