高压对Mg-17Zn-1Y合金凝固组织及力学性能的影响

发布时间：2019-04-01 18:05

【摘要】：以Mg-17Zn-1Y合金作为本文的研究对象,采用OM、SEM、XRD和EDS等分析方法对合金的组织和物相进行研究,探索其在不同压力下(1GPa、2GPa以及3GPa)凝固的的合金在组织、相和力学性能等方面的变化规律,实验得出的数据对于丰富高压凝固理论有一定意义。实验结果表明:均匀化处理后Mg-17Zn-1Y合金的组织中有α-Mg、14H和Mg7Zn3相,Mg7Zn3以长条状、网状分布在基体中,14H相呈现板条状或层片状。高压固溶处理后的合金,固溶压力不断提高,14H相从板条状、层片状变为细板条状和针状,Zn在α-Mg中的含量在常压下为2.44at%;当固溶压力变为1GPa时候达到2.67at%,最后由2GPa时的2.82at%变为3GPa时的3.40at%,而随着固溶压力的增大,Y的含量逐渐减少,从1GPa的0.28at%变为2GPa时的0.12at%,最终减小到3GPa的0.01at%。在1GPa下凝固的合金组织中,Mg-Zn二元相和α-Mg形成共晶组织并且交错形成网状结构,14H以平行方式分布在基体中,形貌为板条状或层片状,同时有部分富Y相分布在基体中。当凝固压力升高到2GPa时,相组成仍然为α-Mg、Mg-Zn二元相以及14H,14H相数量大大增加,同时Mg-Zn二元相体积分数增大,部分网状结构破碎,同时仍有块状和点状的富Y相生成。在3GPa下凝固的合金组织中14H相的含量减少,大部分网状结构消失,组织明显细化,14H相从原来的板条状或层片状变为细针状。当凝固的压力逐渐增大,Y在α-Mg中的固溶度减小,从1GPa下的0.37at%减小至3GPa下的0.07at%,而Zn原子的含量在常压下为2.44at%,当压力升高到1GPa增加到2.58at%,随后从2GPa下的2.76at%升高至3GPa下的3.89at%。固溶、凝固压力对合金的力学性能也有改善,室温的抗拉强度从常态凝固下的48.7MPa强化到3GPa下凝固的139.6MPa,维氏硬度则从1GPa时的113.1HV变为2GPa时的132.3HV,在3GPa时增大至134.2HV。
[Abstract]:The microstructure and phase of Mg-17Zn-1Y alloy solidified under different pressures (1GPa, 2GPa and 3GPa) were studied by means of OM,SEM,XRD and EDS, and the microstructure of the alloy was studied by means of OM,SEM,XRD and EDS. The experimental data can be used to enrich the theory of high pressure solidification due to the variation of phase and mechanical properties. The experimental results show that there are 伪-Mg,14H and Mg7Zn3 phases in the microstructure of Mg-17Zn-1Y alloy after homogenization, and Mg7Zn3 is in the form of long strips and reticulate distribution in the matrix, and the 14H phase is lath or lamellar. After high pressure solution treatment, the solution pressure of the alloy increases continuously. The 14H phase changes from lath, lamellar to thin strip and needle, and the content of Zn in 伪-Mg is 2.44 at% under atmospheric pressure. When the solution pressure changes to 1GPa, it reaches 2.67 at%, and finally changes from 2.82 at% at 2GPa to 3.40 at% at 3GPa. With the increase of solution pressure, the content of Y decreases gradually, from 0.28 at% of 1GPa to 0.12 at% of 2GPa. It finally decreased to 0.01 at% of 3GPa. In the microstructure of alloy solidified under 1GPa, Mg-Zn binary phase and 伪-Mg form eutectic structure and interlaced to form reticulate structure. 14H is distributed in the matrix in a parallel manner, and the morphology is lath or lamellar. At the same time, some Y-rich phases are distributed in the matrix. When the solidification pressure increases to 2GPa, the phase composition is still 伪-Mg,Mg-Zn binary phase and 14H, and the quantity of 14H phase increases greatly. At the same time, the volume fraction of Mg-Zn binary phase increases and some reticular structures break up. At the same time, there are still massive and punctate Y-rich phases. In the microstructure solidified under 3GPa, the content of 14H phase decreased, most of the reticular structure disappeared, and the structure of 14H phase was obviously refined. The 14H phase changed from lath or lamellar to fine needle. When the solidification pressure increases gradually, the solid solubility of Y in 伪-Mg decreases, from 0.37 at% under 1GPa to 0.07 at% at 3GPa, while the content of Zn atom is 2.44 at% at normal pressure, and when the pressure increases to 2.58 at%, the content of Zn atom increases to 2.58 at%. It then rose from 2.76 at% under 2GPa to 3.89 at% under 3GPa. The mechanical properties of the alloy are also improved by solid solution and solidification pressure. The tensile strength at room temperature is enhanced from 48.7MPa at normal solidification to 139.6 MPA at 3GPa, and the Vickers hardness changes from 113.1HV at 1GPa to 132.3HV at 2GPa. Increase to 134.2 HV at 3GPa.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG244;TG146.22

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