Abstract
Pre-stretching was carried out to modify the microstructure of Mg-Nd-Zn-Zr alloy to enhance its age strengthening. The results indicated that more heterogeneous nucleation sites can be provided by the high density of dislocations caused by the plastic pre-stretching deformation, as well as speeding up the growth rate of precipitates. Comparison of microstructure in non-pre-stretched specimens after artificial aging showed that pre-stretched specimens exhibited a higher number density of precipitates. The fine and coarse plate-shaped precipitates were found in the matrix. Due to an increase in the number density of precipitates, the dislocation slipping during the deformation process is effectively hindered, and the matrix is strengthened. The yield strength stabilizes at 4% pre-stretching condition, and then the evolution is stable within the error bars. The 8% pre-stretched specimens can achieve an ultimate tensile strength of 297 MPa. However, further pre-stretching strains after 8% cannot supply any increase in strength. Tensile fracture surfaces of specimens subjected to pre-stretching strain mainly exhibit a trans-granular cleavage fracture. This work indicated that a small amount of pre-stretching strain can further increase strength of alloy and also effectively enhance the formation of precipitates, which can expand the application fields of this alloy.
Highlights
The addition of rare-earth elements (RE) is an effective way to improve the mechanical properties of magnesium alloys [1,2,3,4]
The microstructure of as-cast specimen consists of α-Mg matrix and eutectic compounds
Fine equiaxial α‐Mg grains are separated by eutectic compounds
Summary
The addition of rare-earth elements (RE) is an effective way to improve the mechanical properties of magnesium alloys [1,2,3,4]. The Mg-Nd-Zn-Zr alloy is one of the most successful Mg-RE alloy systems. This alloy shows a highly desirable combination of relative good room-temperature tensile properties and high-temperature creep resistance, both of which are associated with structure, distribution and number density of precipitates [5]. Further attempts to improve the strength of the alloy via controlling the nucleation and growth of precipitates during aging process are rarely reported
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