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研究不同Zn含量的Mg-x%Zn-1%Mn(x=4,5,6,7,8,9)变形镁合金经热机械处理后的显微组织和力学性能的演变。在热挤压过程中,显微组织经动态再结晶得以充分细化。随着Zn含量的增加,动态再结晶晶粒有长大的趋势,然而,随之增加的第二相流线阻碍其长大。固溶处理使动态再结晶晶粒快速长大,但高Zn含量会阻碍晶界迁移,从而使最终的晶粒较为细小。在单级时效过程中,与基体共格的MgZn2弥散相会从过饱和固溶体中析出;在双级时效时,预时效过程中析出的大量纳米尺度的GP区为第二级时效过程中MgZn2相的析出提供了有效的异质形核核心,从而使该强化相的弥散度增加。挤压态试样的力学性能对Zn含量的变化不敏感,抗拉强度在300-320MPa之间波动,伸长率在11%-14%之间波动。时效态试样的强度随着Zn含量的增加以抛物线形式增加,单级时效态试样的抗拉强度从278MPa增加到374MPa,而双级时效态试样的抗拉强度从284MPa增加到378MPa,但所有试样的伸长率都小于8%。当Zn含量超过其在Mg-Zn二元合金体系中的最大固溶度(约6.2%)后,合金的强度增加缓慢但伸长率却迅速降低。因此,含6%Zn的Mg-Zn-Mn合金具有最佳的力学性能,即经过单级和双级时效后,合金的抗拉强度分别为352MPa和366MPa,伸长率分别为8%和5%。
The microstructure and mechanical properties of Mg-x% Zn-1% Mn (x = 4, 5, 6, 7, 8, 9) During hot extrusion, the microstructure is fully refined by dynamic recrystallization. With the increase of Zn content, the dynamic recrystallization grains tend to grow, however, the consequent increase of the second phase flow obstructs the growth. The solid solution treatment rapidly grows the dynamic recrystallized grains, but the high Zn content hinders the grain boundary migration so that the final grains are finer. During the single-stage aging process, the MgZn2 dispersed phase precipitated from the supersaturated solid solution. In the two-stage aging, a large number of nano-scale GP zones precipitated during the pre-aging process are the MgZn2 phase The precipitation provides an effective heterogeneous nucleation nucleus, thereby increasing the dispersion of the reinforcing phase. The mechanical properties of extruded samples are not sensitive to the change of Zn content. The tensile strength fluctuates between 300-320 MPa and the elongation fluctuates between 11% -14%. The strength of the aged specimen increases with the increase of Zn content in the form of a parabola. The tensile strength of the single-stage aged specimen increases from 278 MPa to 374 MPa, while the tensile strength of the two-stage aged specimen increases from 284 MPa to 378 MPa. However, the elongation of all samples was less than 8%. When the Zn content exceeds its maximum solubility in Mg-Zn binary alloy system (about 6.2%), the strength of the alloy increases slowly but the elongation decreases rapidly. Therefore, the 6% Zn-containing Mg-Zn-Mn alloy has the best mechanical properties, namely after single-stage and double-stage aging, the tensile strength of the alloy were 352MPa and 366MPa, elongation of 8% and 5 %.