Al对长周期有序堆垛结构增强的Mg-Y-Zn-Mn合金组织和性能的影响

发布时间：2018-05-13 19:47

  本文选题：长周期有序堆垛结构 + Al合金化　； 参考：《太原理工大学》2017年硕士论文

【摘要】：镁合金是当今最轻的结构金属,具有优良的机加工性能,阻尼减震性良好,比强度、比刚度高和可循环利用的优点,被誉为“21世纪发展前途最大的结构金属材料”,被广泛应用于交通运输,航空航天,消费电子产品和计算机通讯等领域,是近年来国内外材料界的研究热点之一。稀土镁合金因其高强性、高韧性、耐热性好等突出特点,在商用镁合金领域占有重要地位。而长周期有序堆垛结构(LPSO)的发现,进一步提高了稀土镁合金的高温性能和强韧性,国内外学者针对长周期镁合金进行了广泛的研究。本文通过常规铸造制备了含有长周期相的Mg-Y-Zn-Mn-(Al)合金,该合金中生成了一种新的原位自生强化相。通过对铸态合金进行固溶处理和正挤压变形处理,探究了固溶时间和冷却方式以及挤压速度对Mg-Y-Zn-Mn-Al合金微观组织和力学性能的影响,同时探究了Al对18R和14H LPSO转化的影响。除此以外还研究了不同状态下Mg_(93.6)Y_(2.5)Zn_(2.5)Al_(0.4)合金的电化学腐蚀性能,以及富铈混合稀土对Mg-Y-Zn-Mn-(Al)合金的变质作用,主要研究结果如下:(1)Al能够在一定程度上细化枝晶,减小枝晶臂间距;该合金元素的加入能够在基体上生成新的Al(Y,Zn)_2相,起到复合强化的作用,添加量为0.4 at%时,LPSO和Al(Y,Zn)_2相的比例达到最佳,铸态下合金抗拉强度和伸长率达到259 MPa/5.4%。(2)固溶处理的最佳温度为500℃,固溶处理后随炉冷却的合金,W相由网状变为颗粒状;条状18R-LPSO相固溶进基体内然后在冷却过程中以精细的层片状14H-LPSO相析出,同时在层片状14H-LPSO之中夹着0.2μm左右的18R-LPSO相;Al(Y,Zn)_2相由固态下的点状或针状聚集长大,变为鱼骨状。固溶处理后水淬的合金微观组织因为冷却速度太快,没有精细层片状14H-LPSO相析出,基体上只有细小的18R-LPSO相。(3)Al(Y,Zn)_2相对固溶处理时间十分敏感,固溶时间过长该相会发生聚集会导致组织恶化。固溶30 h时合金的力学性能最佳,抗拉强度和伸长率分别为257 MPa和15.4%。(4)正挤压速率对Mg_(93.6)Y_(2.5)Zn_(2.5)Al_(0.4)合金中各相的形貌及动态再结晶的数量和大小有显著影响,速率为30mm/min中Al(Y,Zn)_2相得到充分碎化,分布最弥散,同时动态再结晶的体积分数最大。其力学性能最佳为375 MPa和17.5%。
[Abstract]:Magnesium alloy is the lightest structural metal with excellent machinability, good damping, high specific strength, high specific stiffness and recyclable utilization. It is called "the most promising structural metal material in the 21st century". It is widely used in the fields of transportation, aerospace, consumer electronics and computer communication. It is one of the research hotspots in the field of materials at home and abroad in recent years. Rare earth magnesium alloy plays an important role in commercial magnesium alloy field because of its high strength, high toughness and good heat resistance. The discovery of LPSO (long period ordered stacking structure) has further improved the high temperature properties and strength and toughness of rare earth magnesium alloys. Scholars at home and abroad have carried out extensive research on long period magnesium alloys. In this paper, Mg-Y-Zn-Mn-Al) alloy containing long period phase was prepared by conventional casting, and a new in-situ strengthening phase was formed in Mg-Y-Zn-Mn-Al) alloy. The effects of solution time, cooling mode and extrusion speed on the microstructure and mechanical properties of Mg-Y-Zn-Mn-Al alloy were investigated by solution treatment and forward extrusion treatment. The effects of Al on the transformation of 18R and 14H LPSO were also investigated. In addition, the electrochemical corrosion properties of mg _ S _ (93. 6) / Y _ S _ (2. 5) ~ (2. 5) / S _ (2.5) / S ~ (2 +) -AlN _ 4) alloy and the modification effect of cerium rich rare earth on Mg-Y-Zn-Mn-Al) alloy have been studied. The main results are as follows: (1) 1% Al can refine the dendrite to a certain extent and reduce the dendrite arm spacing; The addition of this alloy element can form a new phase of Al _ 2O _ Y _ O _ Zn _ T _ 2 on the matrix, which plays the role of compound strengthening. The ratio of LPSO and Al-YY _ (Zn) _ (2) is the best when the addition amount is 0.4 at%. The tensile strength and elongation of the as-cast alloy reached 259 MPA / 5.4. The optimum temperature of solution treatment was 500 鈩，

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