DISLOCATION CREEP IN SUPER–LIGHT α SOLID SOLUTION BASE Mg–6Li–3Zn ALLOY
Received date: 2009-09-07
Revised date: 2010-02-06
Online published: 2010-06-11
Supported by
Supported by National Natural Science Foundation of China (Nos.50774023 and 50974038), National High Technology Research and Development Program of China (No.2007AA03Z111) and China Central University Basic Research Transaction Expenses (No.090502003)
Mg–6Li–3Zn alloy was prepared by Jackson’s melting and casting method and the sheets of 1.2 mm in thickness processed by hot rolling at 573 K and cold rolling with a total reduction of more than 92% were obtained. The high–temperature mechanical behavior at temperatures ranging
from 423 to 673 K and initial strain rates ranging from 1.67×10−3 to 5×10−2 s−1 were investigated. The microstructure evolution, such as grains, subgrains, dislocations, cavities and fracture morphology, were investigated by OM, TEM and SEM. Yavari–Langdon model describing the transition between dislocatoviscous glide and dislocation climb was used to construct a new dislocatiocreep mechanism map which consists of Cottrell’s solute atmosphere breakaway dislocation climb regime, dislocation viscous glide regime and Cottrell’s solute atmosphere incorporated dislocation climb regime. A new cavity growth map considering cavity coalescence was obtained according to the cavity growth models. The maximum elongation to failure of 300% was demonstrated at 623 K and an initial strain rate of 1.67×10−3 s−1. Significant dynamic recrystallization occurred in band–like structure at 573 K and an initial strain rate of 1.67×10−3 s−1, the subgrain contour was ambiguous and dislocation distribution was relatively uniform. Fracture mode of the alloy at 573—623 K and an initial strain rate of 1.67×10−3 s−1 is ductile fracture. It is shown by the dislocation creep mechanism map that the high–temperature deformation mechaism in Mg–6Li–3Zn alloy sheet with bad–like structure at 573 K and an initial strain rate of .67×10−3 s−1 is dislocation viscous glide cotrolled by lattice diffusion, the stress exponent is 3 (strain rate sesitivity exponent 0.33) and deformation activation energy is 134.8 kJ/mol, which is the samas the lattice diffusion activation energy of Mg. The cavity growth mechanism of the alloy at 573 K and iitial strain rate of 1.67×10−3 s−1 is plasticity controlled cavity growth.
CAO Fu-Rong , CUI Jian-Zhong , LI Yang-Long , ZHOU Ge , DING Hua . DISLOCATION CREEP IN SUPER–LIGHT α SOLID SOLUTION BASE Mg–6Li–3Zn ALLOY[J]. Acta Metall Sin, 2010 , 46(6) : 715 -722 . DOI: 10.3724/SP.J.1037.2009.00582
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