【摘要】：稀土鎂合金具有密度小、強(qiáng)度高、耐熱性好等特點(diǎn),在輕量化領(lǐng)域有廣泛的應(yīng)用前景。鎂合金具有優(yōu)良的電磁屏蔽性能,目前國內(nèi)外主要對AZ系和ZK系鎂合金的電磁屏蔽性能研究較多,而對稀土鎂合金的研究很少。為了解擠壓變形及T5熱處理對稀土鎂合金的電磁屏蔽性能的影響,本文在屏蔽效能測試的基礎(chǔ)上,結(jié)合OM、SEM、EDS及XRD等材料測試手段,分析了擠壓變形與時(shí)效處理過程中微觀組織的演變與稀土鎂合金電磁屏蔽性能變化的關(guān)系,主要結(jié)論如下:鑄態(tài)Mg-13Gd-4Y-2Zn-0.5Zr鎂合金能夠有效地屏蔽30~1500MHz范圍內(nèi)的電磁波,屏蔽等級達(dá)到了優(yōu)良。在30~1500MHz測試頻率范圍內(nèi),Mg-13Gd-4Y-2Zn-0.5Zr鎂合金的電磁屏蔽效能達(dá)到了86~107dB,而7A04鋁合金和2A12鋁合金的電磁屏蔽效能分別為71~107dB,55~107dB。隨著頻率的上升,電磁波的穿透能力逐漸增強(qiáng),導(dǎo)致電磁屏蔽性能呈下降趨勢。在熱擠壓變形中,隨變形量增加,Mg-13Gd-4Y-2Zn-0.5Zr合金的電磁屏蔽性能逐漸提高。在30~1500MHz測試頻率范圍內(nèi),當(dāng)變形程度為80%時(shí),其電磁屏蔽效能達(dá)到93~107dB。由于合金晶粒隨變形程度增加不斷細(xì)化,導(dǎo)致稀土鎂合金內(nèi)部晶界密度不斷提高,電磁波在合金內(nèi)部傳播中發(fā)生折射和反射的幾率增大,從而增大了電磁波在合金內(nèi)部的吸收損耗和多重反射損耗。另外,在熱擠壓變形中基面織構(gòu)的逐漸增強(qiáng)也增加了合金內(nèi)部的反射損耗。對擠壓態(tài)合金進(jìn)行T5熱處理,隨著時(shí)間的延長,其電磁屏蔽性能逐漸提高,但并沒有隨時(shí)間而單調(diào)變化。峰時(shí)效態(tài)(225℃×24h)稀土鎂合金的電磁屏蔽性能最好,在測試頻率范圍內(nèi)達(dá)到了96~107dB。由于時(shí)效過程中析出了大量呈彌散狀分布的第二相Mg5(GdY)提高了稀土鎂合金的電導(dǎo)率,從而增加了反射損耗和吸收損耗;同時(shí)第二相Mg5(GdY)提高了合金的相界面密度,導(dǎo)致內(nèi)部多重反射損耗增加。但是隨著時(shí)間的繼續(xù)延長,第二相Mg5(GdY)的明顯粗化以及部分晶粒發(fā)生長大,降低了合金內(nèi)部相界面密度和晶界密度,導(dǎo)致合金內(nèi)部多重反射損耗減小。
[Abstract]:Rare earth magnesium alloys have many advantages, such as low density, high strength and good heat resistance. Magnesium alloys have excellent electromagnetic shielding properties. At present, there are many researches on electromagnetic shielding properties of AZ and ZK series magnesium alloys, but few on rare earth magnesium alloys. In order to understand the effect of extrusion deformation and T5 heat treatment on the electromagnetic shielding properties of rare earth magnesium alloys, based on the testing of shielding effectiveness, this paper combines the testing methods of OM,SEM,EDS and XRD, etc. The relationship between the evolution of microstructure during extrusion deformation and aging treatment and the electromagnetic shielding property of rare earth magnesium alloy is analyzed. The main conclusions are as follows: as-cast Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy can effectively shield electromagnetic waves in the range of 30~1500MHz. In the range of 30~1500MHz testing frequency, the electromagnetic shielding efficiency of Mg-13Gd-4Y-2Zn-0.5Zr magnesium alloy is up to 86 ~ 107dB, while that of 7A04 aluminum alloy and 2A12 aluminum alloy is 71 ~ 107dB ~ 55 ~ 107dB, respectively. With the increase of frequency, the penetration ability of electromagnetic wave increases gradually, which leads to the decrease of electromagnetic shielding performance. In hot extrusion deformation, the electromagnetic shielding property of Mg-13Gd-4Y-2Zn-0.5Zr alloy increases with the increase of deformation amount. In the range of 30~1500MHz testing frequency, when the deformation degree is 80, the electromagnetic shielding efficiency reaches 93 ~ 107dB. As the grain size increases with the increase of deformation degree, the grain boundary density of rare earth magnesium alloy increases continuously, and the probability of refraction and reflection of electromagnetic wave in the alloy is increased. Therefore, the absorption loss and multiple reflection loss of electromagnetic wave in the alloy are increased. In addition, the gradual enhancement of the basic texture during hot extrusion also increases the reflection loss in the alloy. The electromagnetic shielding property of extruded alloy increased gradually with the prolongation of time, but it did not change monotonously with time after T5 heat treatment. The peak aging state (225 鈩，

本文編號：2423550