Polysynthetic Twinned High-Performance TiAl Alloy with Ordered Structures of Functional Units

doi:10.11900/0412.1961.2026.00048

Acta Metall Sin

2026, Vol. 62

Issue (4): 541-549 DOI: 10.11900/0412.1961.2026.00048

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Polysynthetic Twinned High-Performance TiAl Alloy with Ordered Structures of Functional Units

CHEN Guang¹^,²^,³(

), CHEN Fengrui¹^,²^,³(

), ZHU Demin¹^,²^,³, LI Guizhong¹^,²^,³, LI Luo¹^,²^,³, SONG Weidong¹^,²^,³, WANG Zite¹^,²^,³, XIANG Henggao¹^,²^,³, CHEN Yang¹^,²^,³, QI Zhixiang¹^,²^,³

^1.State Key Laboratory of Light Superalloys, Nanjing Research Base, Nanjing University of Science and Technology, Nanjing 210094, China
^2.State Key Laboratory of Advanced Casting Technologies, Nanjing University of Science and Technology, Nanjing 210094, China
^3.Nanjing Belight Laboratory, Nanjing 210094, China

Cite this article:

CHEN Guang, CHEN Fengrui, ZHU Demin, LI Guizhong, LI Luo, SONG Weidong, WANG Zite, XIANG Henggao, CHEN Yang, QI Zhixiang. Polysynthetic Twinned High-Performance TiAl Alloy with Ordered Structures of Functional Units. Acta Metall Sin, 2026, 62(4): 541-549.

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Abstract

Transformative TiAl alloys are in high demand for hot-end components such as aeroengine blades and for lightweighting advanced aerospace equipment. However, traditional TiAl alloys are brittle at room temperature and exhibit low long-term capability at high temperatures. To overcome these limitations, our team has proposed a new material-design paradigm based on “ordered structures of functional units.” By precisely regulating the intrinsic characteristics and ordered structures of the soft γ-TiAl phase, the hard α₂-Ti₃Al phase, and nano-twins, we considerably enhance the strength, plasticity, and high-temperature capability of polysynthetic twinned TiAl alloys. We also demonstrate the decisive roles of ordered-structure parameters, such as interface type, lamellar orientation, lamellar thickness, and phase proportion, on the mechanical properties of the alloy. The physical strengthening and toughening mechanisms include twinning-induced strengthening and plasticity in the γ phase, fatigue-strength-enhancing stacking faults in the α₂ phase, toughening via transformation of the α₂ phase, and γ/α₂ coherent interfaces, which improve fracture toughness. These insights illuminate promising directions for the development of TiAl alloys with ordered functional unit structures.

Key words: polysynthetic twinned TiAl alloy functional unit ordered structure strengthening and toughening mechanical property

Received: 09 February 2026

ZTFLH:

TG146.2

Fund: National Natural Science Foundation of China(92463301);National Natural Science Foundation of China(92163215);National Natural Science Foundation of China(52595663);National Natural Science Foundation of China(52571145);National Natural Science Foundation of China(52433016);Advanced Materials-National Science and Technology Major Project(2025ZD0608600);China Postdoctoral Science Foundation(2025M784312);State Key Laboratory of Light Superalloys(sysjj2025101);State Key Laboratory of Light Superalloys(sysjj2025102);State Key Laboratory of Light Superalloys(sysjj2025201);State Key Laboratory of Light Superalloys(sysjj2025202);State Key Laboratory of Light Superalloys(sysjj2025203)

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	Articles by authors
	CHEN Guang
	CHEN Fengrui
	ZHU Demin
	LI Guizhong
	LI Luo
	SONG Weidong
	WANG Zite
	XIANG Henggao
	CHEN Yang
	QI Zhixiang

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https://www.ams.org.cn/EN/10.11900/0412.1961.2026.00048 OR https://www.ams.org.cn/EN/Y2026/V62/I4/541

Fig.1 Types of functional units in polysynthetic twinned TiAl alloys (a1, a2) schematic^[15] (a1) and TEM image^[1] (a2) of α₂ phase and γ phase (b) schematic of slip continuity between geometrically favored slip systems in the γ lamella (tetragon) and α₂ lamellae (hexagonal prisms) (The white arrows denote the strain energy release routes either across or along the γ/α₂ interface)^[21] (c1, c2) schematic (c1) and TEM image^[1] (c2) of Q-type twins within the γ phase (Arrow shows twins. The same in Figs.1d2 and e2) (d1, d2) schematic (d1) and TEM image (d2) of P + Q-type twins within the γ phase (e1, e2) schematic (e1) and TEM image^[27] (e2) of twins within the α₂ phase

Fig.2 Types of interface of polysynthetic twinned TiAl alloy with ordered structures of functional units (a1, a2) γ/α₂ phase interfaces from <1 $1 ¯$ 0] _γ^[29] (a1) and <0 $1 ¯$ 1] _γ (a2) directions (b1, b2) 180° γ/γ true twin (TT) interfaces from <110] $γ A$ ^[29] (b1) and <011] $γ A$ (b2) directions (Where γ_A is the matrix, γ_AT is the 180° TT) (c) 60° γ/γ pseudo twin (PT) interface^[29] (Where γ_B is the 60° PT) (d) 120° γ/γ ordered domain (OD) interface^[29] (Where γ_C is the 120° OD)

Fig.3 Influences of ordered structure parameters on mechanical properties (a1-a4) intrinsic plastic deformation properties (a1) and microstructures related to the lamellar internal orientations of 0° (a2), 45° (a3), and 90° (a4)^[21] (UTS—ultimate tensile strength) (b1-b4) mechanical properties (b1) and microstructures^[33] (b2-b4) of nanoscale α₂ + O phase modulated by 625 ^oC and 5 h heat treatment and then air cooling (AC) (HIP—hot isostatic pressing; red arrow in Fig.3b3 shows nanoscale preci-pitated O phase; T1 and T2 in Fig.3b4 show twin 1 and twin 2, respectively) (c1-c4) mechanical properties (c1) and EBSD images^[34] (c2-c4) after cyclic regulation of the two-phase ratios (c2) initial state (c3) annealed at 1373 K for 6 h (c4) annealed at 1613 K for 6 h

Fig.4 Strengthening and toughening physical mechanisms of high-performance TiAl alloys with ordered structures of functional units
(a) twinning-induced strengthening and plasticity in γ phase^[1,27] (ST—service temperature)
(b) stacking faults enhance fatigue strength in α₂ phase^[18] (PST—polysynthetic twinned, TiAl-TNM—Ti-43Al-4Nb-1Mo-0.1B alloy)
(c) phase transformation induced toughening in α₂ phase^[37] (SISF—superlattice intrinsic stacking fault, APB—antiphase boundary, PB—phase boundary, GSFE—generalized stacking fault energy, CRSS—critical resolved shear stress)
(d) coherent γ/α₂ interfaces enhance fracture toughness^[38] (R_T—toughness ratio, UHC/M—ultra-high carbon steel/mild steel)

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