Crack
initiation and propagation mechanisms of an extruded dual-phase
Magnesium-Lithium alloy in very high cycle fatigue regime
Xiangyu WANG a, Chao HE* a, b, Xue
Li a, Yongjie LIUa, b, Qingyuan
WANG* a, c, Lang LI a,b, Hong ZHANGa, b, Chong WANG a, b
a Key Laboratory of Deep Earth Science and Engineering, Ministry of
Education, College of Architecture and Environment, Sichuan University,
Chengdu 610065, China
b Failure Mechanics & Engineering Disaster Prevention and Mitigation,
Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610065,
China
c School of Architecture and Civil Engineering, Chengdu University,
Chengdu 610106, China
Corresponding authors:
Dr. Chao HE
Sichuan University
Email: hechao@scu.edu.cn
Prof. Qingyuan WANG
Sichuan University
Email: wangqy@scu.edu.cn
Abstract: Ultra-light Mg-Li
alloy is a promising alloy in aerospace since it is known to the
lightest structural alloy at present, but its fatigue behaviors remain
to be explored. This work focuses on very-high cycle fatigue (VHCF)
strength and small crack initiation behaviors of an extruded dual-phase
Mg-Li alloy (LZ91). The fatigue strength of the LZ91 alloy at
109 cycles is about 78 MPa, and the fatigue ratio is
approximately 0.46. Microstructure characterization demonstrates that
fatigue crack tends to initiate from the β-Li phase-enriched region. The
α-Mg phase, presenting <10−10 > fiber texture
with the basal plane, deforms hardly along the extrusion direction and
acts as an enhanced phase compared with the β-Li phase. The deformation
discrepancy localizes cyclic plasticity at the Li phase and finally
leads to the fatigue crack initiation.
Keywords:Magnesium-lithium
alloy; very-high cycle fatigue; crack initiation and propagation;
microstructural sensitivity.