Microstructure evolution and mechanical properties of Mg-x%Zn-1%Mn(x=4,5,6,7,8,9) wrought magnesium alloys  

Mg-x%Zn-1%Mn(x=4,5,6,7,8,9)变形镁合金的组织演变和力学性能(英文)

作　　者：张丁非[1,2] 石国梁[1] 赵霞兵[1] 齐福刚[1] 

机构地区：[1]重庆大学材料科学与工程学院,重庆400045 [2]国家镁合金材料工程技术研究中心,重庆400044

出　　处：《Transactions of Nonferrous Metals Society of China》2011年第1期15-25,共11页中国有色金属学报（英文版）

基　　金：Project(2007CB613700)supported by the National Basic Research Program of China;Project(2007BAG06B04)supported by the National Science and Technology Pillar Program During the 11th Five-Year Plan Period,China;Project(50725413)supported by the National Natural Science Foundation of China;Project(CDJXS10132202)supported by the Fundamental Research Funds for the Central Universities,China

摘　　要：The roles of Zn content and thermo-mechanical treatment in affecting microstructures and mechanical properties of Mg-x%Zn-1%Mn（mass fraction,x=4,5,6,7,8,9） wrought Mg alloys were investigated.The microstructure was extremely refined by dynamic recrystallization（DRC） during extrusion.With increasing Zn content,the DRC grains tended to grow up,at the same time,more second phase streamlines would be present,which restricted the further growing.During solution treatment,the DRC grains would rapidly grow up;however,higher Zn content could hinder the grain boundary expanding,which results in finer ultimate grains.MgZn2 dispersoid particles which are coherent with the matrix would precipitate from the supersaturated solid solution during the one-step aging process,and nano-sized GP zones formed during the pre-aging stage of the two-step aging provide a huge amount of effective nuclei for the MgZn2 phases formed in the second stage,which makes the MgZn2 particles much finer and more dispersed.The mechanical properties of as-extruded samples were not so sensitive to the variation of Zn content,the tensile strength fluctuates between 300 and 320 MPa,and the elongation maintains a high value between 11% and 14%.The strength of aged samples rises as a parabolic curve with increasing Zn content,specifically,the tensile strength of one-step aged samples rises from 278 to 374 MPa,and that of two-step aged ones rises from 284 to 378 MPa,yet the elongation of all aged samples is below 8%.When Zn content exceeds its solid solution limit in Mg-Zn system（6.2%,mass fraction）,the strength rises slowly but the elongation deteriorates sharply,so a Mg-Zn-Mn alloy with 6% Zn possesses the best mechanical properties,that is,the tensile strengths after one-and two-step aging are 352 and 366 MPa,respectively,and the corresponding elongations are 7.98% and 5.2%,respectively.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%。

关 键 词：Mg-Zn-Mn alloy two-step aging AGE-HARDENING Zn content 

分 类 号：TG146.22[一般工业技术—材料科学与工程]