摘要
通过光学显微镜(OM)、电子背散射(EBSD)及单轴拉-压研究了Y元素含量(1%,5%,质量分数)、挤压温度(ET)、挤压比(ER)对Mg-Y合金挤压棒材显微组织、织构及拉-压变形行为的影响规律。结果表明:当Y含量由1%增加到5%(ET=300℃,ER=9):由"双峰"组织变为细小均匀的完全动态再结晶组织;两种棒材横截面(ED面)和纵剖面(TD面)的平均晶粒尺寸相近,约为(14.1±1.9)~(16.5±1.6)μm;室温拉伸屈服强度(TYS)由173±3 MPa降低到125±6MPa,但断裂延伸率则由(11.0±2.1)%大幅增加到了(31.0±1.2)%,这主要是由于基面丝织构的显著弱化和织构强度的明显降低(~53%)导致;CYS/TYS由0.87变为1.10,材料由通常的正拉压不对称性变为反拉压不对称性。当ER由9增加到32(ET=300℃):Mg-1Y的TYS大幅增加到(242±1) MPa(~40%),同时断裂延伸率增加到(12.9±1.5)%(~17%),这主要与大挤压比使得动态再结晶趋于完全、晶粒更加细小均匀(10.1±1.4μm)以及基面丝织构的显著弱化(~75%)密切相关。增加挤压温度(300~400℃)对Mg-1Y棒材(ER=32)的晶粒尺寸和拉伸力学性能的影响较小,但可提高压缩屈服强度(CYS)至(236±9) MPa(~15%),CYS/TYS由0.85增加到1.02,材料拉压屈服对称。Y含量显著影响材料的变形行为,不同挤压参数的Mg-1Y合金棒材均表现出"S"型压缩曲线,而Mg-5Y则无此现象,变形后组织观察表明"S"型曲线与孪晶主导变形密切相关。
Optical microscope(OM),electron back scattering diffraction(EBSD) and uniaxial tension and compression tests were carried out to investigate the effect of Y content(1 wt%,5 wt%),extrusion temperature(ET) and extrusion ratio(ER) on the microstructure,texture and tension-compression deformation behavior of extruded Mg-Y alloy bars.Results show that the grains change from typical bimodal structure to small,homogeneous and fully dynamic recrystallized grains with increasing Y content from 1% to 5%(ET=300 ℃,ER=9).The average grain size of cross section(ED plane) and longitudinal section(TD plane) of the two alloy bars are close and approximately(14.1±1.9) μm~(16.5±1.6) μm.As a result of dramatically weakened basal plane fiber texture and decreasing texture intensity(~53%),the room temperature tensile yield strength(TYS) decreases from(173±3) MPa to(125±6) MPa while elongation remarkably rises from(11.0±2.1)% to(31.0±1.2)%.Furthermore,the tension-compression asymmetry changes from common(CYS/TYS=0.8) to inverse(CYS/TYS=1.10) with increasing of Y content.With the extrusion ratio increasing from 9 to 32(ET=300 ℃),the TYS of Mg-1 Y alloy bars drastically increases to(242±1) MPa(~40%),and the elongation increases to(12.9±1.5) MPa(~17%),which may be closely related to fully dynamic recrystallization,finer grain size(~10.1±1.4 μm) and obviously weakened basal plane fiber texture(~75%).The increasing extrusion temperature(300~400 ℃) has little effect on grain size and tension mechanical properties of Mg-1 Y alloy bars(ER=32) while compression yield strength(CYS) rises to(236±9) MPa(~15%),the value of CYS/TYS changes from 0.85 to 1.02 which means the alloy exhibits tension-compression symmetry.Y content has an obvious influence on the deformation behavior of extruded Mg-Y alloy bars.All of the extruded Mg-1 Y alloy bars show sigmoid compression stress-strain curve while no similar phenomenon in Mg-5 Y alloy bar is observed.Observation of microstructure after compression suggests that this phenomenon is closely related to twining dominant deformation mechanism.
作者
黄广号
李欣
尹冬弟
陆嘉伟
周浩
权高峰
Huang Guanghao;Li Xin;Yin Dongdi;Lu Jiawei;Zhou Hao;Quan Gaofeng(Key Laboratory for Advanced Technologies of Materials,The Ministry of Education of China,Southwest Jiaotong University,Chengdu 610031,China;Beijing University of Technology,Beijing 100022,Chain)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2018年第9期2861-2868,共8页
Rare Metal Materials and Engineering
基金
国家自然科学基金(青年项目)(51401172
51601003)
四川省科技计划(2015HH0012)
中央高校基本科研业务费专项资金(2682016CX073)
关键词
镁钇合金
挤压参数
拉压不对称性
显微组织
力学性能
magnesium-yttrium alloy
extrusion parameters
tension-compression asymmetry
microstructure
mechanical properties.