scholarly journals Nucleation of {1012} Twins in Magnesium through Reversible Martensitic Phase Transformation

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1030
Author(s):  
Jamie Ombogo ◽  
Amir Hassan Zahiri ◽  
Tengfei Ma ◽  
Lei Cao

We report the discovery of a rigorous nucleation mechanism for {101¯2} twins in hexagonal close-packed (hcp) magnesium through reversible hcp-tetragonal-hcp martensitic phase transformations with a metastable tetragonal phase as the intermediate state. Specifically, the parent hcp phase first transforms to a metastable tetragonal phase, which subsequently transforms to a twinned hcp phase. The evanescent nature of the tetragonal phase severely hinders its direct observation, while our carefully designed molecular dynamics simulations rigorously reveal the critical role of this metastable phase in the nucleation of {101¯2} twins in magnesium. Moreover, we prove that the reversible hcp-tetragonal-hcp phase transformations involved in the twinning process follow strict orientation relations between the parent hcp, intermediate tetragonal, and twin hcp phases. This phase transformation-mediated twinning mechanism is naturally compatible with the ultrafast twin growth speed. This work will be important for a better understanding of the twinning mechanism and thus the development of novel strategies for enhancing the ductility of magnesium alloys.

2017 ◽  
Vol 73 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Heidrun Sowa

Martensitic transformations which play an important role in metallurgical processes are analysed using group–subgroup relations and sphere-packing considerations. This approach is applied to the transformations between body-centred cubic (b.c.c.) and face-centred cubic (f.c.c.) phases and yields the orientation relations according to the Nishiyama–Wassermann, the Kurdjumov–Sachs and the Pitsch mechanisms. The models proposed by Pitsch and Schrader and by Burgers for the transition between b.c.c. and hexagonally closest-packed (h.c.p.) type structures can be interpreted analogously. In addition, two mechanisms for the transition between cubic f.c.c. and h.c.p. structures are described.


2018 ◽  
Author(s):  
Naiara I. Vázquez Fernández ◽  
Tuomo Nyyssönen ◽  
Matti Isakov ◽  
Mikko Hokka ◽  
Veli-Tapani Kuokkala

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