微合金化与热处理对Al-Mn系合金组织及高温性能的影响

发布时间：2018-03-27 07:18

  本文选题：Al-Mn系合金　切入点：微合金化　出处：《东南大学》2017年硕士论文

【摘要】：复合钎焊式热交换器的生产工艺和工作环境要求热交换器用铝合金具有一定的耐高温性能,本文在典型Al-Mnu系3003合金的基础上添加了不同的合金元素,研究微合金化和热处理工艺对热交换器用芯材Al-Mn系合金再结晶过程及组织的影响,结合合金微观组织的有效控制和蠕变机理,研究了合金元素对Al-Mn系合金高温力学性能,尤其是高温蠕变性能的影响。本文首先研究了合金元素对Al-Mn系合金退火组织的影响。结果表明:Mg、Cu、Ce、La可细化合金退火晶粒,Mg和Ni或Mg和Zr联合添加促进了退火晶粒的长条状程度;Mg促进了AlMnSi相的析出,Ni增加了化合物的种类和数量(AlMnFeSiNi相、AlMnSiNi相),Ce/La的加入形成了较多的AlRESi稀土化合物。此外,Al-Mn、Al-Mn-0.3Mg、Al-Mn-0.3Mg-0.2Ni和Al-Mn-0.3Mg-0.2Zr合金退火过程中沉淀相析出与再结晶相互作用的临界温度Tc分别为396℃、405℃、430℃和433℃;冷轧Al-Mn合金在600℃(高于Tc)退火,再结晶先于析出,得到细小等轴晶;而先经350℃(低于Tc)退火处理,析出先于再结晶,获得沿轧制方向分布的长条状晶粒,因率先析出的AlMnSi等相尺寸较小,再在600℃下退火仍具有抑制晶界法向移动的作用,最终保持有利于蠕变性能的长条状组织。对Al-Mn系合金进行了高温拉伸性能和蠕变性能测试。结果表明:单独添加0.3%Mg对Al-Mn系合金高温性能的改善效果好于单独添加0.1%Ni;所有合金中Al-Mn-0.3Mg-0.2Ni(S4)合金具有最佳的高温性能,200℃和250℃下高温抗拉强度分别达到131MPa和lO1MPa(提高了90%和98%),200℃/40MPa条件下稳态蠕变速率ε=5.71×10-9s-1比Al-Mn合金(ε=8.80×10-8s-8s-1)低一个数量级,而250℃/40MPa条件下稳态蠕变速率从5.07×l06s-l减至3.93×10-8s-1降低了两个数量级;Al-Mn-0.3Mg-0.2Zr合金在250℃/40MPa条件下稳态蠕变速率ε=5.21×10-8s-1,对Al-Mn合金蠕变性能的改善仅次于S4合金。Mg和Ce/La联合添加时,合金的高温强度、抗蠕变性能进一步提高,但由于晶粒组织发生细化,改善效果并不明显。研究了Al-Mn系合金在175～250℃、外加应力25～50MPa条件下的蠕变行为,运用幂指数方程建立了 Al-Mn系合金稳态蠕变本构方程。结果表明:Al-Mn合金在175℃下蠕变应力指数n=3.4,蠕变过程受位错粘滞性滑移控制;在200～250℃下,蠕变受位错攀移控制(n=5.9～8.3);合金元素Mg或Mg和Ni/Zr的联合添加使Al-Mn合金在200～225℃下,蠕变仍受位错粘滞性滑移控制(n=2.9～3.9),而位错粘滞性滑移速率低于位错攀移速率,抗蠕变性能提高。此外,蠕变前后沉淀相TEM结果表明,Al-Mn系合金的高温性能与沉淀相析出量和种类有关,析出量及种类越多、结构越复杂,对位错运动(粘滞性滑移、攀移)和晶界滑动的阻碍作用越大,相应合金的高温性能越好。
[Abstract]:The production process and working environment of composite brazing heat exchanger require aluminum alloy for heat exchanger to have certain high temperature resistance. Different alloying elements are added to the typical Al-Mnu 3003 alloy in this paper. The effect of microalloying and heat treatment on recrystallization process and microstructure of Al-Mn series alloy for heat exchanger was studied. Combined with the effective control of microstructure and creep mechanism, the high temperature mechanical properties of Al-Mn series alloy were studied. In this paper, the effect of alloying elements on the annealing microstructure of Al-Mn alloys is studied. The results show that the grain size of the alloy can be refined by the addition of mg and Ni or the addition of mg and Zr to the annealed alloy. The results show that the addition of mg and Ni or mg and Zr can promote the annealed grain. In addition, the addition of AlMnFeSiNi phase and AlMnFeSiNi phase can form more AlRESi rare earth compounds. In addition, the precipitated phase and recrystallized phase of Al-MnFeSiNi phase and Al-Mn-0.3Mg-0.2Zr alloy are precipitated and recrystallized in the annealing of Al-MnMn-0.3Mgn-0.3Mg-0.2Ni and Al-Mn-0.3Mg-0.2Zr alloy. The critical temperature of interaction is 396 鈩，

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