【作者】 胡楠楠；

【导师】 邱克强； 李庆丰；

【作者基本信息】 沈阳工业大学 ， 材料学， 2009， 硕士

【摘要】 Mg基非晶合金复合材料具有比强度高、塑性好等优点,在微成形部件等方面具有应用前景,因此成为非晶合金领域的研究热点。本文通过铜模铸造法制备了Mg-Ni（Cu）-Zn-Y非晶合金及其复合材料,采用扫描电镜（SEM）、X-射线衍射仪（XRD）分析合金的组织、断口形貌和相组成,利用电子万能试验机测试合金的力学性能,主要实验结果如下:对比研究了直径为3mm的Mg₇₇Cu₁₂Zn₅Y₆和Mg₇₇Ni₁₂Zn₅Y₆两种合金,这两种合金的断裂强度和塑性应变量分别为532MPa、2.4%和667MPa、7%。非晶基体上晶态相组成不同是这两种合金力学性能差别的主要原因。通过对应力-应变曲线的分析,给出了非晶合金复合材料的塑性变形机制。研究了Mg和Ni的变化对Mg_77+xNi_12-xZn₅Y₆（x=4,6,8）合金组织结构和力学性能的影响。随着Ni含量的减少,Mg2Ni相逐渐减少,析出的Mg₁₂YZn相增多,针状Mg相的数量和尺寸减少。当Ni的含量为8%时,合金的压缩塑性有了突破性进展达到了21%,但因非晶含量不高,所以强度仅为550MPa。在Ni为6at%和4at%时合金的断裂强度分别为640MPa和600MPa,塑性变形量分别为15.8%和17%。研究了Mg和Y的变化对Mg_73+xNi₁₂Zn₅Y_10-x（x=0,2,6,8）合金组织结构和力学性能的影响。随着Y含量的减少,非晶基体上晶态相的形貌由x=0时的花瓣状发展为x=6时的针叶状和x=8时的粗大枝晶状。其中x=2合金的非晶基体上仅有少量的花瓣与针叶的混合组织。其中Mg₇₃Ni₁₂Zn₅Y₁₀合金具有最佳的压缩断裂强度和塑性,分别为692MPa和4%。当将Ni降低到8at%时,设计了Mg_87-xNi₈Zn₅Y_x（x=2,4,8）非晶合金复合材料,调整Mg和Y的含量,没有改善合金的力学性能。样品的制备尺寸提高,降低了Mg₇₅Ni₁₂Zn₅Y₈和Mg₇₇Ni₁₂Zn₃Y₈合金的力学性能。更多还原

【Abstract】 The high specific strength and good plasticity for Mg-based amorphous matrix composites （AMC） make them have many potential applications in such as micro electro mechanical system. Therefore the search for Mg-based AMC with higher plastic deformation has become a highlight in the development of bulk metallic glasses. In this paper, Mg-Ni（Cu）-Zn-Y amorphous matrix composites were prepared by copper mould casting. The microstructure, the fracture surfaces and the phase constituent of those alloys were analyzed by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The mechanical properties of the AMC were tested by universal electronic material testing machine. The results are given as following:Comparative investigations were made for Mg₇₇Cu₁₂Zn₅Y₆ and Mg₇₇Ni₁₂Zn₅Y₆ as-cast alloys with 3mm in diameter. The fracture strength and plastic strain are 532MPa and 2.4% for the former and 667MPa, 7% for the latter. The different crystalline phases in the amorphous matrix result in the different mechanical properties for the two alloys. Furthermore, the plastic deformation mechanism is suggested by analyzing the stress-strain curves.The microstructure and mechanical properties for Mg_77+xNi_12-xZn₅Y₆（x=4, 6, 8） alloys were investigated by considering both Mg and Ni variation. The homogenous distribution of needle-like Mg phase was only observed for x=4 alloy and it decreased with the decrease of Ni element. At the same time, the intermetallic Mg₂Ni was increased and Mg₁₂YZn phase was increased. It is interesting to find that the plastic strain for the alloy with x=4 is as high as 21%, which is the largest plastic strain found up to now. The fracture strengths and plastic strains are 640MPa and 15.8% for x=6 alloys, respectively, 600MPa and 17% for x=8 alloys, respectively.The microstructure and mechanical properties for Mg_73+xNi₁₂Zn₅Y_10-x（x=0, 2, 6, 8） alloys were investigated by decreasing Y and increasing Mg content. The microstructure evolution from flower-like for x=0 to needle-like for x=6 and then to thick dendritic for x=8 alloys respectively. While a combination microstructure containing both flower and needle Mg solid solution was observed for x=2 alloy, which presents the best mechanical properties among the alloys mentioned above. The fracture strength and plastic strain for it are 692MPa and 4% respectively. When we further decreased Ni content and re-designed Mg_87-xNi₈Zn₅Y_x（x=2, 4, 8） alloys, however, the mechanical properties of the new alloys were not improved. The effect of cooling rate on the mechanical properties was also investigated. The fracture strength and plastic strain were becoming worse when as-cast sample size was increased for both Mg₇₅Ni₁₂Zn₅Y₈ and Mg₇₇Ni₁₂Zn₃Y₈ alloys.更多还原