【作者】 张大华；

【导师】 陈体军；

【作者基本信息】 兰州理工大学 ， 材料学， 2010， 硕士

【摘要】 镁合金是目前工业应用最轻质的金属材料,具有巨大的发展潜力,日益受到材料工作者的广泛青睐。成为继钢铁、铝之后第三大金属工程材料,被誉为“21世纪绿色工程材料”。然而普通镁合金的强度不高,传统的高强高韧镁合金一般含有较高的稀土元素,这大大提高了其生产成本。因此,研究与开发低成本的高强高韧镁合金显得十分必要。本文以ZW21合金(2.0%Zn,1.0%Y,0.5%Nd,0.5%Sn,0.3%Zr和0.05%Ca)为基础,研究Zn、Y、Nd、Sn、Zr与Ca等合金元素对其组织及力学性能的影响,同时研究了热处理工艺对ZW21合金的组织及力学性能的影响。结果表明：在ZW21合金中,各添加元素对合金的组织有着重要的影响。其中Zn、Y、Nd不同的加入量会使合金中组织形貌和相成分发生变化。Mg、Zn、RE(Y或者Nd)元素之间会形成三元二次相,合金中Zn/RE的值决定了组织中二次相的组成：当Zn/RE小于0.60时,二次相为H相；当Zn/RE为0.60～0.85时,二次相为H相+W相；当Zn/RE为0.85～2.05时,二次相为W相；当Zn/RE为2.05～5.00时,二次相为W相+I相。ZW21合金铸态的抗拉强度为207MPa,伸长率为16.9%,硬度为52.8HV。ZW21合金铸态组织由α-Mg相和W相组成,在525℃固溶处理4小时后水淬,变为单一的α-Mg相,然后在250℃时效处理过程中析出W相。时效处理(250℃×24h)使ZW21合金的力学性能得到提高。其中抗拉强度、伸长率和硬度分别增加到243MPa、20.8%和58.7HV,与铸态相比,时效态合金的抗拉强度提高了17.4%,伸长率提高了23.1%,硬度提高了11.2%。更多还原

【Abstract】 Magnesium alloys as the lightest structural metallic materials have large application potential in the industry and become more and more attractive for material researchers. It is becoming the third largest metal structural materials following steels and aluminum alloys, known as the "21st Century Green Engineering Materials". However, the mechanical properties of most commonly used magnesium alloy are very low. But the cost of high strength and high toughness magnesium alloys are high because they always high content of RE. Therefore, research and development low-cost of high strength and high toughness magnesium alloys is very necessary. In this thesis, the effects of Zn, Y, Nd, Sn, Zr and Ca contents on microstructure and mechanical properties of ZW21 alloy (2.0%Zn,1.0%Y,0.5%Nd,0.5%Sn, 0.3%Zr and 0.05%Ca) have been investigated. In addition, the effect of heat treatment on microstructure and mechanical properties of ZW21 alloy have been studied. The results are shown as followings:The additions of the above alloying elements have large effect on the microstructure. The addition of different amounts of Zn, Y and Nd can change the microstructure.morpgologies and phase constitutes. The phases containing Mg, Zn, RE (Y or Nd) are determined by Zn/RE ratio:the formed phase(s) should be H-phase, H-phase+W-phase, W-phase and W-phase+ I-phase When Zn/RE ratio is less than 0.60, and in the ranges of 0.60～0.85,0.85～2.05,2.05～5.00, respectively.The tensile strength, elongation and hardness of ZW21.alloy are 207MPa, 16.9%,52.8HV, respectively. It as-cast microstructure is consisted ofα-Mg+W-phase. After being solutionized at 525°C for 4h, it evolves into a uniqueα-Mg phase. During the subsequently ageing at 250°C, the W-phase graudually precipitates. Ageing treatment (24h at 250°C) can improve the mechanical properties of the ZW21 magnesium. Compared with the as-cast ZW21 alloy, the tensile strength, elongation and hardness of aged alloy are increased by 17.4%,23.1% and 11.2%, respectively.更多还原