Process thermokinetics influenced microstructure and corrosion response in additively in-situ manufactured Ti-Nb-Sn and Ti-Nb alloys - Journal of Manufacturing Processes 152 (2025)

Jul 30, 2026

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This study investigates how process thermokinetics affect microstructural evolution, mechanical properties, and corrosion behavior in Ti-25Nb-5Sn (wt.%) produced by laser powder bed fusion using mechanically blended elemental powders. Columnar grains form with mixed phases and un-melted Nb particles embedded in the matrix. A multiscale finite element thermokinetic model links processing parameters to observed microstructure changes. Sn addition increases ductility via enhanced mass evaporation and recoil pressure, causing incomplete Nb melting and preferential galvanic corrosion; martensite fraction further controls corrosion resistance.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Abstract

Introduction

Biomedical motivation for Ti alloys

Role of Sn and Nb in phase stability and properties

Additive manufacturing and in-situ alloying challenges

Materials and process parameters

Journal of Manufacturing Processes 152 (2025) 427–441 | Process thermokinetics influenced microstructure and corrosion response in additively in-situ manufactured Ti-Nb-Sn and Ti-Nb alloys
Selvamurugan Palaniappana,b, Shashank Sharmaa,b, Madhavan Radhakrishnan a,b,
K.V. Mani Krishna b, Sameehan S. Joshia,b, Rajarshi Banerjee a,b, Narendra B. Dahotrea,b ,∗ a Department of Materials Science and Engineering, University of North Texas, 3940 N Elm St, Denton, TX 76207, USA
b Center for Agile and Adaptive Additive Manufacturing, University of North Texas, 3940 N Elm St, Denton, TX 76207, USA | | | | | --- | --- | --- | --- | | A R T I C L E I N F O | | A B S T R A C T | | | Keywords:
Ti-Nb-Sn alloy
L-PBF process Microstructural evolution Corrosion
Mechanical properties | | This study investigated the influence of process thermokinetics on the microstructural evolution, mechanical properties, and corrosion behavior of Ti-25Nb-5Sn (wt.%) alloy fabricated via laser powder bed fusion using mechanically blended elemental precursor powder. The microstructures of all Ti-25Nb-5Sn specimens processed with various sets of processing parameters evolved into columnar grains consisting of a mixture of 􀀋′′ and 􀀌 phases, with un-melted Nb embedded in the matrix. A multi-scale finite element method-based thermokinetic model was employed to reveal the process parameter associated thermokinetics and resultant evolution of the microstructure. The addition of Sn significantly enhances the ductility of the alloy, demonstrating a twofold improvement compared to Ti-25Nb (wt.%). Notably, the low boiling point of Sn generates higher mass evaporation rate and higher recoil pressure within the melt pool, leading to incomplete melting of Nb. The presence of un-melted Nb particles contributed to preferentially galvanic corrosion compared to fully alloyed Ti-25Nb resulting in an increased corrosion current density. Additionally, the martensite fraction played a critical role in influencing the corrosion behavior, as Ti-25Nb fabricated by laser powder bed fusion at 200 Wand 330 mm/s exhibited superior corrosion resistance. | | 1. Introduction 􀀌 Titanium (Ti) alloys stand out as promising candidates for the next generation of biomedical alloys when compared to conventional options such as Co-Cr-Mo alloys, stainless steels, Ti-Ni alloys, pure Ti, and Ti-6A-4V [1]. This distinction arises from their outstanding properties, including high strength, superior corrosion resistance, and excellent biocompatibility [2–4]. These properties can also be finely tuned through processes associated thermokinetics-dependent phase transformations and compositional adjustments. In Ti-alloys, the 􀀌 phase exhibits the lowest modulus (E), followed by 􀀋′′, 􀀋′, 􀀋, and 􀀡 phases [5]. Achieving a Young’s modulus closer to that of bone is crucial in biomedical alloys to mitigate issues such as stress shielding. Among 􀀌-type Ti-alloys, Ti–Nb alloys have emerged as particularly promising candidates for advanced biomedical applications due to their low elastic modulus (E), high strength, and excellent biocompatibility [4,6,7]. Additionally, studies have shown that the addition of Sn to Ti-Nb alloys suppresses the formation of the 􀀡 phase, thereby reducing the Young’s modulus and enhancing the ductility [8]. Moreover, Sn acts as a strong solid-solution strengthener, contributing to improved mechanical strength [2]. Several studies have reported that cold-rolled and annealed Ti-33Nb-4Sn (wt.%) alloys exhibit an ideal combination of a low Young’s modulus (36 GPa) and high strength (853 MPa), attributed to a fine-grained 􀀌-Ti microstructure with a high dislocation density [9–13]. While conventional fabrication techniques such as casting, arc melting, and hot rolling have been extensively studied for the production of Ti–Nb alloys [4,7,14], additive manufacturing (AM) technologies, particularly laser powder bed fusion (L-PBF), have recently gained significant attent

FAQs

How does Sn influence the microstructure and melting of Nb during L-PBF of Ti-25Nb-5Sn?

Sn’s low boiling point increases mass evaporation rate and recoil pressure in the melt pool, promoting incomplete melting of Nb. This leads to un-melted Nb particles embedded in the matrix.

What thermokinetic modeling approach is used to connect processing parameters to microstructure evolution?

A multi-scale finite element method-based thermokinetic model is employed to reveal the thermokinetics associated with specific process parameters and the resulting microstructural evolution.

Why does the presence of un-melted Nb affect corrosion behavior?

Un-melted Nb particles cause preferential galvanic corrosion compared with fully alloyed Ti-25Nb. This increases corrosion current density relative to specimens without un-melted Nb.

Jul 30, 2026

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