含难熔元素高熵合金的成分设计及其性能研究
发布时间：2018-11-22 11:10
【摘要】：高熵合金是一种新型金属材料,具有独特的结构和优异的性能,因此受到广泛的关注。本课题用真空电弧熔炼法制备了含有难熔金属元素的CuYZr/Al,Ti,Hf、CuxYxZrTiHf(x=0.6,1.0,摩尔比)和AlxHfNbTiZr(x=0、0.5、0.75、1.0、1.25和1.5,摩尔比)系列高熵合金。较为系统地分析了这些高熵合金的物相结构和组织形貌,测试了热学参数、力学性能、海水耐蚀性等性能,探讨了合金成分对高熵合金结构和各项性能的影响机制。主要研究结果如下:1.三种CuYZr/Al,Ti,Hf高熵合金的主要结构都由密排六方(HCP1)树枝晶和存在于枝晶间的体心立方(BCC)结构CuY型化合物相组成。特别地,富Hf的HCP2固溶体相和少量非晶相分别出现在CuYZrAlHf和CuYZrAlTi高熵合金中。Hf、Ti和Zr元素集中分布在HCP1和HCP2固溶体中,这表明HCP结构元素能促进高熵合金中HCP固溶体的形成。CuYZrTiHf高熵合金的压缩屈服强度为1340 MPa,断裂方式为塑性断裂;而CuYZrAlHf和CuYZrAlTi高熵合金具有更高的强度和硬度,断裂方式为脆性断裂。富Hf-HCP2相和非晶相的存在能阻碍位错运动,起到明显强化作用,大幅降低了CuYZrAlHf和CuYZrAlTi合金的塑性。海水溶液中的电化学腐蚀测试表明,三种合金枝晶间的CuY型化合物发生了明显的腐蚀,而HCP树枝晶耐蚀性良好。此外,CuYZrAlTi合金具有较好的耐点蚀性。2.铸态CuxYxZrTiHf高熵合金由HCP固溶体相和位于枝晶间的CuY化合物相组成。通过同时改变Cu、Y两种元素的含量,能够调节这两种物相在高熵合金中的体积分数。其中,Cu0.6Y0.6ZrTiHf合金的HCP相体积分数增多,CuY相明显减少。两种合金在1400℃以下没有出现熔化现象。Cu0.6Y0.6ZrTiHf高熵合金的塑性较好,但硬度和压缩强度略低于CuYZrTiHf合金。CuY化合物和HCP固溶体的体积分数主要决定了高熵合金力学性能的差异。海水耐蚀性测试表明,Cu0.6Y0.6ZrTiHf合金出现了二次钝化行为,具有较好的局部耐点蚀性。对Cu0.6Y0.6ZrTiHf和CuYZrTiHf合金样品进行缓慢预形变(变形量10%)后,其强度和硬度都有小幅提升,但后者的塑性大幅下降。此外,预形变显著改善了这两种合金的海水耐蚀性。3.在AlxHfNbTiZr高熵合金(简称为Alx)中,Al0和Al0.5高熵合金由单一的无序BCC固溶体组成。除无序固溶体外,Al0.75~Al1.5高熵合金中新生成了有序BCC固溶体,且这两相的晶格常数很接近。较低的混合焓和价电子浓度有助于AlxHfNbTiZr高熵合金中有序固溶体的形成。在1400℃以下,AlxHfNbTiZr高熵合金未出现熔化现象。Al添加导致了高熵合金力学性能的显著变化。随着Al含量升高,脆硬的有序BCC相增多,合金的强度、硬度大幅提高,塑性变形能力明显下降。AlxHfNbTiZr高熵合金的强化机制有固溶强化、有序固溶体强化和细晶强化。Al添加有效降低了高熵合金的密度,提升了强度,从而大幅提升了合金的比强度。Al0合金具有良好的海水耐蚀性。Al添加后,合金的钝化区宽度减小,其表面发生了明显的点蚀现象,海水耐蚀性下降。
[Abstract]:High entropy alloy is a new metal material with unique structure and excellent properties. In this paper, a series of high entropy alloys containing refractory metal elements, CuYZr/Al,Ti,Hf,CuxYxZrTiHf (x = 0.6N, 1.0, mole ratio) and AlxHfNbTiZr (x = 0. 5, 0. 75, 0. 05), were prepared by vacuum arc melting (VARF). The phase structure and microstructure of these high entropy alloys were systematically analyzed. The thermal parameters, mechanical properties and corrosion resistance of seawater were tested. The mechanism of the effect of alloy composition on the structure and properties of high entropy alloys was discussed. The main results are as follows: 1. The main structures of the three kinds of CuYZr/Al,Ti,Hf high entropy alloys are composed of dense hexagonal (HCP1) dendrites and bulk centered cubic (BCC) (BCC) structure CuY compounds which exist between dendrites. In particular, Hf rich HCP2 solid solution phase and a small amount of amorphous phase appear in CuYZrAlHf and CuYZrAlTi high entropy alloys respectively. Hf,Ti and Zr elements are concentrated in HCP1 and HCP2 solid solution. The results show that HCP structure element can promote the formation of HCP solid solution in high entropy alloy. The compressive yield strength of CuYZrTiHf high entropy alloy is 1340 MPa, and the fracture mode is plastic fracture. CuYZrAlHf and CuYZrAlTi high entropy alloys have higher strength and hardness, and the fracture mode is brittle fracture. The existence of rich Hf-HCP2 phase and amorphous phase can hinder dislocation movement, play an obvious strengthening role, and greatly reduce the plasticity of CuYZrAlHf and CuYZrAlTi alloys. The electrochemical corrosion test in aqueous solution shows that the CuY type compounds of three kinds of alloy dendrites are obviously corroded, while the HCP dendrites have good corrosion resistance. In addition, CuYZrAlTi alloy has good pitting corrosion resistance. The as-cast CuxYxZrTiHf high entropy alloy consists of HCP solid solution phase and CuY compound phase located between dendrites. By changing the content of Cu,Y two elements at the same time, the volume fraction of these two phases in high entropy alloy can be adjusted. The volume fraction of HCP phase increases and CuY phase decreases obviously in Cu0.6Y0.6ZrTiHf alloy. The two alloys have no melting phenomenon below 1400 鈩，
本文编号：2349180
[Abstract]:High entropy alloy is a new metal material with unique structure and excellent properties. In this paper, a series of high entropy alloys containing refractory metal elements, CuYZr/Al,Ti,Hf,CuxYxZrTiHf (x = 0.6N, 1.0, mole ratio) and AlxHfNbTiZr (x = 0. 5, 0. 75, 0. 05), were prepared by vacuum arc melting (VARF). The phase structure and microstructure of these high entropy alloys were systematically analyzed. The thermal parameters, mechanical properties and corrosion resistance of seawater were tested. The mechanism of the effect of alloy composition on the structure and properties of high entropy alloys was discussed. The main results are as follows: 1. The main structures of the three kinds of CuYZr/Al,Ti,Hf high entropy alloys are composed of dense hexagonal (HCP1) dendrites and bulk centered cubic (BCC) (BCC) structure CuY compounds which exist between dendrites. In particular, Hf rich HCP2 solid solution phase and a small amount of amorphous phase appear in CuYZrAlHf and CuYZrAlTi high entropy alloys respectively. Hf,Ti and Zr elements are concentrated in HCP1 and HCP2 solid solution. The results show that HCP structure element can promote the formation of HCP solid solution in high entropy alloy. The compressive yield strength of CuYZrTiHf high entropy alloy is 1340 MPa, and the fracture mode is plastic fracture. CuYZrAlHf and CuYZrAlTi high entropy alloys have higher strength and hardness, and the fracture mode is brittle fracture. The existence of rich Hf-HCP2 phase and amorphous phase can hinder dislocation movement, play an obvious strengthening role, and greatly reduce the plasticity of CuYZrAlHf and CuYZrAlTi alloys. The electrochemical corrosion test in aqueous solution shows that the CuY type compounds of three kinds of alloy dendrites are obviously corroded, while the HCP dendrites have good corrosion resistance. In addition, CuYZrAlTi alloy has good pitting corrosion resistance. The as-cast CuxYxZrTiHf high entropy alloy consists of HCP solid solution phase and CuY compound phase located between dendrites. By changing the content of Cu,Y two elements at the same time, the volume fraction of these two phases in high entropy alloy can be adjusted. The volume fraction of HCP phase increases and CuY phase decreases obviously in Cu0.6Y0.6ZrTiHf alloy. The two alloys have no melting phenomenon below 1400 鈩，
本文编号：2349180
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