FeCrVTi基高熵合金微观组织及性能研究

发布时间：2018-08-22 09:09

【摘要】：高熵合金是一种新型合金设计理念,具有较高的混合熵,从而抑制金属间化合物的出现,获得简单结构的固溶体组织。高熵合金具有高强度、高硬度、优异的高温力学性能等特性,并且高熵合金的成分选择灵活,能发挥各主元的特性,具有广泛的潜在应用。耐高温、抗辐照的结构材料是核反应堆的关键材料,高熵合金概念的提出为开发此材料提供了新的思路。本文以FeCrVTi系高熵合金为对象,研究了元素添加及含量的改变和热处理工艺对高熵合金微观组织及力学性能的影响,得到的主要结论如下:添加不同的元素对等摩尔比FeCrVTi系高熵合金的微观组织和力学性能有很大的影响。合金主要由BCC相组成,其硬度与合金体系的Ω值成反比,合金比较脆,大多在弹性阶段就发生断裂。由BCC1及BCC2相组成的FeCrVTiMo高熵合金具有较高的屈服强度,其铸态抗压强度随温度的升高而先升高然后降低,断裂方式由脆断变为韧断。在1250 oC高温均匀化12 h后,合金的抗压强度和塑性下降程度较少,而经过700 oC长时间的时效处理后,合金出现共析反应有初生α钛相析出,合金的塑性及抗压强度下降。为了提高合金的力学性能,基于价电子浓度理论,设计了Fe_(3.5)Cr_(1.2)V_(1.5)Ti_(1.5)Mn_1X_(0.3)(X=Mo,W)非等摩尔比高熵合金。结果表明,铸态合金的组织较为均匀,在高温下仍能保持较高的抗压强度。经700 oC时效处理之后,有初生及次生α钛相出现,细小弥散的次生α钛相可以提高合金的抗压强度,但随着时效时间的延长,次生α钛相长大导致合金的力学性能下降。相较于FeCrVTiMo高熵合金,Fe_(3.5)Cr_(1.2)V_(1.5)Ti_(1.5)Mn_1X_(0.3)系高熵合金经长时间时效过后抗压强度有显著提高。为了使合金中具有FCC相并提高合金的塑性,设计了价电子浓度值为7.95的Fe_(35)Cr_(20)Mn_(10)Cu_(25)V_(10)高熵合金。研究发现其由BCC结构的母相和具有纳米尺寸的FCC富铜析出相组成。铸态合金的屈服强度为577 MPa,压缩应变大于10%,塑性较好。经700℃,1500 h时效之后,合金的硬度和屈服强度增加。
[Abstract]:High entropy alloy is a new kind of alloy design concept with high mixing entropy, which can restrain the appearance of intermetallic compounds and obtain simple structure of solid solution structure. High entropy alloy has high strength, high hardness, excellent high temperature mechanical properties and other characteristics, and the composition of high entropy alloy is flexible to choose, can play the characteristics of each principal component, with the high entropy alloy. Wide potential applications. High temperature resistant and irradiation resistant structural materials are the key materials for nuclear reactors. The concept of high entropy alloy provides a new idea for the development of this material. The main conclusions are as follows: the addition of different elements has a great influence on the microstructure and mechanical properties of high entropy FeCrVTi alloys with equal molar ratio. The as-cast compressive strength of o-high entropy alloy increases first and then decreases with the increase of temperature, and the fracture mode changes from brittle fracture to ductile fracture. In order to improve the mechanical properties of the alloy, the Fe_ (3.5) Cr_ (1.2) V_ (1.5) Ti_ (1.5) Mn_1X_ (0.3) (X = Mo, W) non-equimolar ratio high entropy alloy was designed based on the valence electron concentration theory. The results show that the microstructure of as-cast alloy is uniform and the compressive strength can be maintained at high temperature. After oC aging treatment, primary and secondary Alpha-titanium phases appear. Fine and dispersed secondary Alpha-titanium phases can improve the compressive strength of the alloy, but with the aging time prolonged, the growth of secondary Alpha-titanium phase leads to the decrease of mechanical properties of the alloy. A high entropy Fe_ (35) Cr_ (20) Mn_ (10) Cu_ (25) V_ (10) alloy with valence electron concentration of 7.95 was designed to have FCC phase in the alloy and improve the plasticity of the alloy. The hardness and yield strength of the alloy increase after aging at 700 C for 1500 H.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139

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