Role of Constitutional Supercooling in Grain Refinement Mechanisms of Additively Manufactured Ti–Cu Alloys

Jayshri Dumbre; Ryan Brooke; Duyao Zhang; Raj Das; Dong Qiu; Mark Easton

doi:10.1007/s11661-026-08126-x

Role of Constitutional Supercooling in Grain Refinement Mechanisms of Additively Manufactured Ti–Cu Alloys

Jayshri Dumbre
, Ryan Brooke
, Duyao Zhang
, Raj Das
, Dong Qiu
, Mark Easton

RMIT University

Research output: Contribution to journal › Article › peer-review

Abstract

Abstract: Additively manufactured Ti–8.5Cu alloy has attracted growing interest due to its distinctive microstructure, characterized by fine equiaxed grains and ultra-fine pearlite. However, the primary grain refining mechanism remains unclear due to the formation of pearlite. This study investigates the role of constitutional supercooling (CS) in directed energy deposition—laser beam/metals processed thin-walled Ti–Cu alloys with varying Cu concentrations, by deliberately suppressing pearlite. The absence of pearlite allows for the reconstruction of parent β-Ti grains using the Burgers orientation relationship on electron-backscattered diffraction maps. The results reveal that the CS during solidification, induced by Cu solute addition, significantly refines grains. Additionally, lower laser energy density also promotes grain refinement that can be attributed to the increased thermal undercooling induced by a higher cooling rate. This research quantifies CS under pearlite-suppressed condition to understand its contribution to grain refining mechanisms in Ti–Cu alloys, offering pathways to control the mechanical properties of eutectoid alloy systems.

Original language	English
Pages (from-to)	1251-1260
Journal	Metallurgical and Materials Transactions A
Volume	57
Early online date	4 Feb 2026
DOIs	https://doi.org/10.1007/s11661-026-08126-x
Publication status	Published - 31 Mar 2026

Funding

Open Access funding enabled and organized by CAUL and its Member Institutions. This work was supported by the Australian Research Council (ARC, Grant Number DP 220101501). We acknowledge the facilities, and the scientific and technical assistance, of the RMIT Advanced Manufacturing Precinct (AMP) and the RMIT Microscopy and Microanalysis Facility (RMMF). This work was performed in part at the RMIT Micro Nano Research Facility (MNRF) in the Victorian Node of the Australian National Fabrication Facility (ANFF).

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CAUL

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title = "Role of Constitutional Supercooling in Grain Refinement Mechanisms of Additively Manufactured Ti–Cu Alloys",

abstract = "Abstract: Additively manufactured Ti–8.5Cu alloy has attracted growing interest due to its distinctive microstructure, characterized by fine equiaxed grains and ultra-fine pearlite. However, the primary grain refining mechanism remains unclear due to the formation of pearlite. This study investigates the role of constitutional supercooling (CS) in directed energy deposition—laser beam/metals processed thin-walled Ti–Cu alloys with varying Cu concentrations, by deliberately suppressing pearlite. The absence of pearlite allows for the reconstruction of parent β-Ti grains using the Burgers orientation relationship on electron-backscattered diffraction maps. The results reveal that the CS during solidification, induced by Cu solute addition, significantly refines grains. Additionally, lower laser energy density also promotes grain refinement that can be attributed to the increased thermal undercooling induced by a higher cooling rate. This research quantifies CS under pearlite-suppressed condition to understand its contribution to grain refining mechanisms in Ti–Cu alloys, offering pathways to control the mechanical properties of eutectoid alloy systems.",

author = "Jayshri Dumbre and Ryan Brooke and Duyao Zhang and Raj Das and Dong Qiu and Mark Easton",

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AU - Dumbre, Jayshri

AU - Brooke, Ryan

AU - Zhang, Duyao

AU - Das, Raj

AU - Qiu, Dong

AU - Easton, Mark

PY - 2026/3/31

Y1 - 2026/3/31

N2 - Abstract: Additively manufactured Ti–8.5Cu alloy has attracted growing interest due to its distinctive microstructure, characterized by fine equiaxed grains and ultra-fine pearlite. However, the primary grain refining mechanism remains unclear due to the formation of pearlite. This study investigates the role of constitutional supercooling (CS) in directed energy deposition—laser beam/metals processed thin-walled Ti–Cu alloys with varying Cu concentrations, by deliberately suppressing pearlite. The absence of pearlite allows for the reconstruction of parent β-Ti grains using the Burgers orientation relationship on electron-backscattered diffraction maps. The results reveal that the CS during solidification, induced by Cu solute addition, significantly refines grains. Additionally, lower laser energy density also promotes grain refinement that can be attributed to the increased thermal undercooling induced by a higher cooling rate. This research quantifies CS under pearlite-suppressed condition to understand its contribution to grain refining mechanisms in Ti–Cu alloys, offering pathways to control the mechanical properties of eutectoid alloy systems.

AB - Abstract: Additively manufactured Ti–8.5Cu alloy has attracted growing interest due to its distinctive microstructure, characterized by fine equiaxed grains and ultra-fine pearlite. However, the primary grain refining mechanism remains unclear due to the formation of pearlite. This study investigates the role of constitutional supercooling (CS) in directed energy deposition—laser beam/metals processed thin-walled Ti–Cu alloys with varying Cu concentrations, by deliberately suppressing pearlite. The absence of pearlite allows for the reconstruction of parent β-Ti grains using the Burgers orientation relationship on electron-backscattered diffraction maps. The results reveal that the CS during solidification, induced by Cu solute addition, significantly refines grains. Additionally, lower laser energy density also promotes grain refinement that can be attributed to the increased thermal undercooling induced by a higher cooling rate. This research quantifies CS under pearlite-suppressed condition to understand its contribution to grain refining mechanisms in Ti–Cu alloys, offering pathways to control the mechanical properties of eutectoid alloy systems.

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JO - Metallurgical and Materials Transactions A

JF - Metallurgical and Materials Transactions A

ER -

Role of Constitutional Supercooling in Grain Refinement Mechanisms of Additively Manufactured Ti–Cu Alloys

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