scholarly journals Relationship between martensitic plate size and austenitic grain size in martensitic transformations

2015 ◽  
Vol 106 (22) ◽  
pp. 221903 ◽  
Author(s):  
P. La Roca ◽  
L. Isola ◽  
Ph. Vermaut ◽  
J. Malarría
Keyword(s):  
Grain Size ◽  
Martensitic Transformations ◽  
Martensitic Plate ◽  
Plate Size ◽  
Austenitic Grain Size

scholarly journals Effect of Added Elements, Especially Titanium, on the Coarsening Temperature of Austenitic Grain Size.

1963 ◽  
Vol 49 (6) ◽  
pp. 894-900 ◽  
Author(s):  
Akira ADACHI ◽  
Kiyoshi MIZUKAWA ◽  
Kakuo KANDA
Keyword(s):  
Grain Size ◽  
Austenitic Grain Size

Austenite in Steel

2015 ◽  
pp. 133-162
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Hot Deformation ◽  
Parent Phase ◽  
Austenite Formation ◽  
Processing Conditions ◽  
Austenitic Grain Size

Austenite is the key to the versatility of steel and the controllable nature of its properties. It is the parent phase of pearlite, martensite, bainite, and ferrite. This chapter discusses the importance of austenite, beginning with the influence of austenitic grain size and how to accurately measure it. It then describes the principles of austenite formation and grain growth and examines several time-temperature-austenitizing diagrams representing various alloying and processing conditions. The chapter concludes with a discussion on hot deformation and subsequent recrystallization.

Martensitic Transformations and Functional Stability in Ultra-Fine Grained NiTi Shape Memory Alloys

2008 ◽  
Vol 584-586 ◽  
pp. 852-857 ◽  
Author(s):  
Juri Burow ◽  
Egor Prokofiev ◽  
Christoph Somsen ◽  
Jan Frenzel ◽  
Ruslan Valiev ◽  
...  
Keyword(s):  
Grain Size ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Thermomechanical Processing ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Coarse Grained ◽  
Functional Stability ◽  
Fine Grained ◽  
Niti Shape Memory Alloys

Martensitic transformations in NiTi shape memory alloys (SMAs) strongly depend on the microstructure. In the present work, we investigate how martensitic transformations are affected by various types of ultra-fine grained (UFG) microstructures resulting from various processing routes. NiTi SMAs with UFG microstructures were obtained by equal channel angular pressing, high pressure torsion, wire drawing and subsequent annealing treatments. The resulting material states were characterized by transmission electron microscopy and differential scanning calorimetry (DSC). The three thermomechanical processing routes yield microstructures which significantly differ in terms of grain size and related DSC chart features. While the initial coarse grained material shows a well defined one-step martensitic transformation on cooling, two-step transformations were found for all UFG material states. The functional stability of the various UFG microstructures was evaluated by thermal cycling. It was found that UFG NiTi alloys show a significantly higher stability. In the present work, we also provide preliminary results on the effect of grain size on the undercooling required to transform the material into B19’ and on the related heat of transformation.

Functional Properties of Ti-Ni-Based Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 156-161 ◽  
Author(s):  
I. Khmelevskaya ◽  
Sergey Prokoshkin ◽  
Vladimir Brailovski ◽  
K.E. Inaekyan ◽  
Vincent Demers ◽  
...  
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Functional Properties ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Critical Temperatures ◽  
Recoverable Strain ◽  
Ultrafine Grained

The main functional properties (FP) of Ti-Ni Shape Memory Alloys (SMA) are their critical temperatures of martensitic transformations, their maximum completely recoverable strain (er,1 max) and maximum recovery stress (sr max). Control of the Ti-Ni-based SMA FP develops by forming well-developed dislocation substructures or ultrafine-grained structures using various modes of thermomechanical treatment (TMT), including severe plastic deformation (SPD). The present work shows that TMT, including SPD, under conditions of high pressure torsion (HPT), equal-channel angular pressing (ECAP) or severe cold rolling followed by post-deformation annealing (PDA), which creates nanocrystalline or submicrocrystalline structures, is more beneficial from SMA FP point of view than does traditional TMT creating well-developed dislocation substructure. ECAP and low-temperature TMT by cold rolling followed by PDA allows formation of submicrocrystalline or nanocrystalline structures with grain size from 20 to 300 nm in bulk, and long-size samples of Ti-50.0; 50.6; 50.7%Ni and Ti-47%Ni-3%Fe alloys. The best combination of FP: sr max =1400 MPa and er,1 max=8%, is reached in Ti-Ni SMA after LTMT with e=1.9 followed by annealing at 400°C which results in nanocrystalline (grain size of 50 to 80 nm) structure formation. Application of ultrafine-grained SMA results in decrease in metal consumption for various medical implants and devices based on shape memory and superelastiсity effects.

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