Experimental and theoretical investigation of crystallography and variant selection during massive transformation in Zr alloy

Rapid cooling of TiAl-based alloy from α phase (disordered hexagonal, A3) generates  phase (ordered tetragonal, L1o) grains through massive transformation nucleating mostly over the α/α grain boundaries. This current work deals with the identification and the validation of different nucleation mechanisms during  massive transformation in TiAl-based alloys. Special attention has been given to the variant selection criteria for the nucleation of the massive structures along different types of α/α grain boundaries. The  massive domains formed along the grain boundaries were analysed using high resolution electron backscattered diffraction (EBSD). Statistical studies were made on different nucleation sites and different mechanisms are proposed. Two–dimensional studies of the nucleation mechanism suggest that the minimization of the interfacial energy could be the predominant criteria during the grain boundary nucleation. In order to verify this nucleation criterion in three-dimensions, serial sections were made and EBSD maps were taken and analysed in each section. The variant selection observed during the nucleation and the growth of the  massive grains is further discussed after getting a broader view under three-dimensional investigations.

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Probability based ranking approach for twin variant selection in an α-Zr alloy

International Journal of Plasticity ◽

10.1016/j.ijplas.2019.06.015 ◽

2019 ◽

Vol 122 ◽

pp. 164-187 ◽

Cited By ~ 2

Author(s):

G. Bharat Reddy ◽

Rajeev Kapoor ◽

Apu Sarkar

Keyword(s):

Variant Selection ◽

Twin Variant ◽

Zr Alloy

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Probability Based Ranking Approach to Twin Variant Selection: A Study on α-Zr Alloy

SSRN Electronic Journal ◽

10.2139/ssrn.3365115 ◽

2019 ◽

Author(s):

G. Bharat Reddy ◽

Rajeev Kapoor ◽

Apu Sarkar

Keyword(s):

Variant Selection ◽

Twin Variant ◽

Zr Alloy

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Microtwinning Evidence For The Apparent Five-Fold Symmetry in T2(Al6Li3Cu)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125178 ◽

1987 ◽

Vol 45 ◽

pp. 24-25

Author(s):

Kenneth S. Vecchio ◽

David B. Williams

Keyword(s):

Stable Equilibrium ◽

Equilibrium Phase ◽

Convergent Beam Electron Diffraction ◽

Icosahedral Structure ◽

Cubic Crystals ◽

Icosahedral Phases ◽

Heat Treated ◽

Zero Layer ◽

Convergent Beam ◽

Zr Alloy

Since the discovery in 1984 by Shechtman et al. of crystals which display apparent five-fold symmetry, extensive effort has been given to establishing a theoretical basis for the existence of icosahedral phases (eg.2.). Several other investigations have been centered on explaining these observations based on twinning of cubic crystals (eg.3.). Recently, the existence of a stable, equilibrium phase T2Al6 Li3Cu) possessing an icosahedral structure has been reported in the Al-Li-Cu system(4-6).In the present study an Al-2.6wt.%Li-l.5wt.%Cu-0.lwt.%Zr alloy was heat treated at 300°C for 100hrs. to produce large T2 precipitates. Convergent Beam Electron Diffraction (CBED) patterns were obtained from two-fold, three-fold, and apparent five-fold axes of T2 particles. Figure 1 shows the five-fold symmetric zero layer CBED pattern obtained from T2 particles.

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Deformation and fracture behavior of an Al-Li-Cu-Mg-Zr alloy 8090

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178008 ◽

1990 ◽

Vol 48 (4) ◽

pp. 974-975

Author(s):

D.M. Jiang ◽

B.D. Hong

Keyword(s):

High Strength ◽

Deformation And Fracture ◽

Fracture Behaviors ◽

Aluminum Lithium ◽

Carbon Fiber Reinforced Composites ◽

Peak Aged ◽

Aluminum Lithium Alloys ◽

High Strength Aluminum Alloys ◽

Lithium Alloys ◽

Zr Alloy

Aluminum-lithium alloys have been recently got strong interests especially in the aircraft industry. Compared to conventional high strength aluminum alloys of the 2000 or 7000 series it is anticipated that these alloys offer a 10% increase in the stiffness and a 10% decrease in density, thus making them rather competitive to new up-coming non-metallic materials like carbon fiber reinforced composites.The object of the present paper is to evaluate the inluence of various microstructural features on the monotonic and cyclic deformation and fracture behaviors of Al-Li based alloy. The material used was 8090 alloy. After solution treated and waster quenched, the alloy was underaged (190°Clh), peak-aged (190°C24h) and overaged (150°C4h+230°C16h). The alloy in different aging condition was tensile and fatigue tested, the resultant fractures were observed in SEM. The deformation behavior was studied in TEM.

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