What is it about?

In this work, novel post-processing treatmnets are developed to homogenize the microstructure and eliminate the cracks existing in the mcrostructure of parts which are LPBF printed from a Ni-rich Ni-Ti elemental powder mixture consisting of about 63 wt.% Ni and 37 wt.% Ti.

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Why is it important?

Ni-rich Ni-Ti alloys, such as 60NiTi, show a higher hardness and dimensional stability than equiatomic or near-equiatomic NiTinol ones. These make them suitable to be employed in structural applications. Printing processes have the potential to manufacture geometrically complex parts reducing the amount of machining needed to obtain the desired final geometry. However, it is a hard task to control the different exothermic reactions, resulting in the generation of different phases such as NiTi, Ni3Ti, Ni3Ti2 and etc., occurred during the LPBF process of the Ni-Ti blended powder systems. It is commonly observed that the microstructure of the parts obtained from elementally mixed Ni-Ti powders suffer from inhomogeneity and is consisted of other undesired intermetallic phases, pure nickel, and pure titanium. In addition, due to the high cooling rates of the LPBF process and inherent brittleness of Ni-rich Ni-Ti parts, cracks are formed in the microstructure of the printed parts. This study provides a solution to eliminate these microstructural defects by proposing novel post-processing treatments.

Perspectives

The outcome of this work is currently getting used by our team as a guideline to process 60NiTi, a superelastic intermetallic having outstanding properties used in bearing applications, in a cost-effective way from an elementally mixed Ni-Ti powder mixture.

Dr Khashayar Khanlari
Auckland University of Technology

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This page is a summary of: An investigation into the possibility to eliminate the microstructural defects of parts printed using a Ni-rich Ni-Ti elemental powder mixture, Materials Research Express, September 2020, Institute of Physics Publishing, DOI: 10.1088/2053-1591/abbc3f.
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