| dc.description.abstract | Abstract
Because of the emergence of environmental protection consciousness and the coming
of high oil price, the energy saving and the green have become the most important subjects
in recent years. Magnesium alloys not only have the characteristics of low specific weight,
high specific strength, and recycling, but also have great performance on anti-impact and
anti-EMI (electronmagnetic interference). Because of these inherent characteristics,
magnesium alloys have widely been used in transportation and 3C (computer,
communication, and consumer electronic) industries. Besides, doping some lithium in
magnesium alloys makes the new magnesium alloys have lower specific weight, higher
specific strength, and better machinability. It can be expected that the magnesium alloys
with lithium doping will have an important role in the future.
ECAE (equal channel angular extrusion) can fine the grain size of materials and widely
be used in magnesium alloys researches. However, there are just few literatures discussed
the applications of ECAE on Mg-Li-Zn alloys. In this research, it studied the effects of the
control parameters of ECAE on the microstructures and mechanical properties of five
different Mg-Li-Zn alloys.
After collecting, observing, and studying the experiment results, some conclusions had
been gotten, and they are stated as below. (1) ECAE can improve the hardness, tension
strength, yield strength of these five Mg-Li-Zn alloys but lower their ductility. (2)ECAE can
make theα-phase of these five Mg-Li-Zn alloys finer, divided, and even spheralized to
prevent the dislocation move of the β-phase and get better strength. (3)The first ECAE
process has the greatest strength improvement in the five annealed Mg-Li-Zn alloys. (4)After
four times ECAE process, LZ91 has the greatest yield strength. (5)The 90° ECAE process has
greater strength improvement in these five Mg-Li-Zn alloys than the 120° one. (6)Because the
finer α-phase can stop the growth of theβ-phase to get better superplasticity during high
temperature tension test, LZ91 has 350% ductility in the 250℃ and 1x10-3s-1test conditions
of the high temperature tension test. (7)In higher stain rate condition ( > 1x10-3s-1), LZ111 and
LAZM9310 have better superplasticity among these five Mg-Li-Zn alloys. | en_US |