Effect of Nb addition on the plastic behavior of TiAI crystals containing oriented lamellae

Journal Article · Sun Nov 15 04:00:00 EST 1992 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(92)90066-N· OSTI ID:7187940

Nakano, T; Yokoyama, A; Umakoshi, Y ^[1]

---

1. Osaka Univ., Suita (Japan). Faculty of Engineering

TiAl has been focussed on as a potential high temperature material because of its high strength-to-weight and good oxidation resistance. One of the major problems to be solved before practical application is the improvement of ductility of low temperatures. Ti-rich TiAl containing a well-developed lamellar structure composed of [alpha][sub 2] and [gamma] phases shows higher strength and better ductility than the single phase Al-rich TiAl. The mechanical properties of TiAl alloys are well known to be strongly affected by the details of the lamellar structure. In this paper, the authors succeed in obtaining binary TiAl crystal s (48.1 [approximately] 51.6at%Al) containing a single set of lamellae with different lamellar spacings by altering the crystal growth rate and the alloy composition. The mechanical properties are closely related to their lamellar structures and the yield stress is represented as a function of the reciprocal square root of the lamellar spacing similar to a Hall-Petch type relation. Furthermore, the authors find that the deformation mode of the [alpha][sub 2] phase in the lamellae strongly affects the plastic behavior of lamellar TiAl crystals. When the compressive axis is parallel to the lamellar planes ([phi]=0[degrees]), shear deformation occurs across them and 10[bar 1]0 [lt]1[bar 2]10 [lt] slip can be activated in the [alpha][sub 2] phase. Addition of niobium to Ti[sub 3]Al is known to activate the motion of [lt]11Ba26[gt] type dislocations of 22[bar 2]1 and to improve the ductility. Therefore, in this paper we report the mechanical properties and microstructure of ternary TiAl crystal containing 1.2at%Nb with a single set of lamellae, focussing on the effect of the deformation model t-of the [alpha][sub 2] phase.

• OSTI ID: 7187940
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 27:10; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
360104 -- Metals & Alloys-- Physical Properties
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM ALLOYS
CHEMICAL COMPOSITION
CORROSION RESISTANCE
CRYSTAL STRUCTURE
DEFORMATION
DUCTILITY
GRAIN ORIENTATION
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
ORIENTATION
PLASTICITY
STOICHIOMETRY
TENSILE PROPERTIES
TITANIUM ALLOYS