铝锌镁合金以其优异的力学性能广泛应用于航空、航天、交通运输等工业领域,而铝合金的细化一直是铝加工行业的研究重点.为细化晶粒并提高其力学性能,本文将传统细化剂Al-Ti-B与RE复合添加到铝锌镁合金中,借助于XRD、光学显微镜、扫描电镜、拉伸实验等测试方法研究了不同细化剂对Al7Zn2.4Mg合金组织及其力学性能的影响.试验结果表明,合金中加入Al-5Ti-B和Al-Zr-Er后细化效果明显,单独添加Al-Ti-B的细化效果最好,但仍有少部分的晶粒保留的树枝晶形态.随着Al-Ti-B和Al-Zr-Er添加量的增多,合金的晶粒发生明显变化,塑性也随之增加,其中,添加0.4wt.％Al-5Ti-B细化剂对合金的塑性影响最大,而抗拉强度呈先增大后减小的趋势,复合添加0.2wt.％Al-2Zr～Er和0.2wt.％Al-5Ti-B细化剂的合金晶粒圆整且未出现树枝晶,晶界析出物最少平均抗拉强度最高.Al-Ti-B和Al-Zr-Er均可细化铸态铝锌镁合金的晶粒,同时添加两种细化剂更有利于提高合金的综合力学性能.
Al-Zn-Mg alloys have been extensively used for structural applications in aerospace and transportation industry due to their excellent mechanical properties.Moreover,the grain refinement of aluminum allolys is the research focus these years.In order to refine grain size and enhance the mechanical properties of Al-Zn-Mg alloys,traditional refiner Al-5Ti-B and RE were added into the cast alloy.The mechanical behavior of Al7Zn2.4Mg alloys with different Al-5Ti-B and Al-2Zr-Er addition was investigated using X-ray diffractometry (XRD),optical microscopy (OM),scanning electron microscopy (SEM) and mechanical test (MET).The experimental results show that the addition of Al-2Zr-Er and Al-5Ti-B can significantly refine the grain size.However,some dendrites still remain at the mere addition of Al-Ti-B as refiner.At the same time,plasticity increases with the addition of Al-Ti-B and Al-Zr-Er.The specimen which has 0.4wt.％Al-STi-B has the most obvious effect on its plasticity,whereas the result is not the same for tensile strength.The tensile strength of the specimen first increases then decreases with the contents of Al-Ti-B increasing.Alloys with 0.2wt.％Al-2Zr-Er and 0.2wt.％ Al-5Ti-B contents change the growth morphology from dendritic to fine equiaxed grain.It exhibits less precipitation on the grain boundary and higher tensile strength during tensile test.The experimental results show that both two refiners can significantly refine the grain size,but co-addition of 0.2wt.％Al-2Zr-Er and 0.2wt.％ Al-5Ti-B is more useful to its comprehensive mechanics performance.
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