非晶孕育对Al-Cu合金组织和强塑性的影响规律及机制

发布时间：2018-03-10 15:46

本文选题：Al-Cu合金　切入点：非晶合金孕育剂　出处：《吉林大学》2015年博士论文　论文类型：学位论文

【摘要】：随着科技进步、环境保护和节省资源的需求，对材料轻量化的要求越来越迫切，开发高强塑性铝合金成为国内外科研工作者的研究热点之一。而通过孕育处理细化铝合金晶粒来提高铝合金的力学性能是简单、常用、有效的方法之一。目前，常用的铝合金孕育剂为晶体形态，主要有Al-Ti-B和Al-Ti-C等中间合金。而采用非晶合金作为铝合金孕育剂的研究报道少见。对于非晶合金作为孕育剂细化铝合金-Al晶粒的机制和提高强塑性的机制并不清楚。因此，研究非晶合金孕育对铸造Al-Cu合金组织和强塑性的影响规律与机制，对开发出新的铝合金孕育剂、丰富铝合金孕育理论及扩大非晶的应用范围具有重要的理论意义和实际应用价值。本文主要围绕非晶合金孕育对铸造Al-Cu合金的组织细化和强塑性的影响规律与机制进行研究。揭示非晶合金孕育对细化铸造Al-Cu合金-Al晶粒的影响规律及其作用机制；不同非晶合金抗孕育衰退机制和非晶合金孕育对铸造Al-Cu合金室温、高温强塑性的影响规律与机制。本文主要研究结果如下： 1）发现ZrCuAlNi、ZrCuAlNiLa、FeBSi和NiNbTi四种非晶合金细化Al-Cu合金的-Al晶粒由强到弱的顺序为ZrCuAlNi非晶ZrCuAlNiLa非晶NiNbTi非晶FeBSi非晶，它们细化-Al晶粒的最小尺寸分别约为35m，38m，39m和41m；上述四种非晶有效孕育时间由长到短的顺序为NiNbTi非晶=FeBSi非晶ZrCuAlNiLa非晶ZrCuAlNi非晶，它们的有效孕育时间分别为30min，30min，10min和3min。其中，在ZrCuAlNi非晶合金中添加稀土La元素可将ZrCuAlNi非晶的有效孕育时间从3min提高到10min。 2）揭示出非晶合金孕育Al-Cu合金中的纳米θ′析出相与未孕育合金的相比，尺寸显著减小，数量明显增多，分布更加均匀。其机制主要为非晶合金孕育处理细化了Al-Cu合金的-Al晶粒，从而使晶界长度明显增加，这有利于合金在凝固过程中晶界处的第二相分布更加均匀。并且由于晶粒尺寸变小，使在固溶处理时第二相由晶界向晶内的扩散距离减小，从而使Cu原子在-Al基体中分布更加均匀。导致在时效过程中纳米θ′析出相的析出激活能降低，使大量的纳米θ′析出相能够更加容易的同时形核、析出、生长，造成纳米θ′析出相生长所需Cu原子的缺乏，从而限制了纳米θ′析出相的生长，使θ′析出相的直径和厚度变小。 3）发现非晶合金孕育处理Al-Cu合金与未孕育合金相比室温强度和塑性都得到了同时提高，其强度和断裂应变提高的规律与非晶合金孕育细化Al-Cu合金-Al晶粒尺寸的规律基本一致。依据强度和塑性综合提高的原则，四种非晶合金孕育处理对Al-Cu合金强塑性同时提高由强到弱的规律为：(Zr55Cu30Al10Ni5)97.2La2.8孕育合金Zr55Cu30Al10Ni5孕育合金Ni60Nb25Ti15孕育合金Fe79.58B11.16Si9.26孕育合金，它们最佳的强度和断裂应变分别为536MPa和16.3%，569MPa和11.1%，531MPa和14.0%，520MPa和14.2%；分别比未孕育合金提高了14.0%和123%，19.7%和58.5%，12.9%和100%，10.6%和102%。揭示出非晶孕育Al-Cu合金强塑性同时提高的主要机制是晶粒细化和纳米θ′析出相细化的共同作用结果。 4）首次揭示ZrCuAlNi、ZrCuAlNiLa、FeBSi和NiNbTi四种非晶合金细化Al-Cu合金-Al晶粒的机制：四种非晶合金加入到Al-Cu合金熔体中，发生晶化，分别形成Zr2Cu、ZrCu(B2)、Fe2B和NiTi晶化相，这些晶化相可以作为-Al相异质形核核心，，从而使-Al晶粒得到了明显细化。提出了非晶合金能够作为Al-Cu合金孕育剂的准则：非晶合金的晶化相应满足作为-Al相异质形核核心的条件。 5）揭示出FeBSi和NiNbTi非晶有效孕育时间比ZrCuAlNi非晶有效孕育时间长的原因是作为-Al相异质形核核心的Fe2B和NiTi晶化相的熔点高于Zr2Cu和ZrCu(B2)晶化相；在ZrCuAlNi非晶中添加稀土La元素可以把ZrCuAlNi非晶合金的有效孕育时间从3min提高到10min，这主要是由于稀土La能够提高作为-Al相异质形核核心的Zr2Cu和ZrCu(B2)晶化相的高温稳定性。 6）提出开发Al-Cu合金长效非晶合金孕育剂的准则为：提高作为-Al相异质形核核心的晶化相在Al-Cu合金熔体中的稳定性。其途径是提高作为-Al相异质形核核心晶化相的熔点；或者通过向非晶孕育剂中添加合金元素，提高作为-Al相异质形核核心晶化相的高温稳定性。 7）揭示出未孕育合金、ZrCuAlNi和ZrCuAlNiLa非晶合金孕育处理Al-Cu合金的高温变形机制均是位错攀移机制。发现在温度433K~493K和应变速率10-4~10-1s-1范围内，非晶合金孕育处理的Al-Cu合金中的纳米θ′析出相比未孕育合金中的纳米θ′析出相尺寸细小，数量多，分布均匀。所以导致位错运动更加困难，从而使非晶合金孕育处理的Al-Cu合金的热变形激活能明显高于未孕育合金的。因此，ZrCuAlNi和ZrCuAlNiLa非晶合金孕育Al-Cu合金的高温强塑性明显优于未孕育Al-Cu合金。 8）提出FeBSi非晶合金是一种细化Al-Cu合金-Al晶粒的孕育时间长、细化效果好、成本低廉的孕育剂。
[Abstract]:With the progress of science and technology, environmental protection and saving resources demand for lightweight materials increasingly urgent requirements, the development of high strength plastic Aluminum Alloy has become a hot research topic at home and abroad researchers. Through inoculation Aluminum Alloy grain refinement to improve the mechanical properties of Aluminum Alloy is simple, common, one of the effective methods at present. Aluminum Alloy, commonly used as inoculant crystal morphology, mainly Al-Ti-B and Al-Ti-C master alloy. And the amorphous alloy as Aluminum Alloy inoculation agent reported rare. For the amorphous alloy as the mechanism of inoculant -Al grain refinement Aluminum Alloy and improve the mechanism of plasticity is not clear. Therefore, the research on amorphous influence and mechanism of the alloy has the casting microstructure of Al-Cu alloy and strong plasticity, to develop new Aluminum Alloy inoculant, rich Aluminum Alloy inoculation theory and expand the scope of application of amorphous out It has important theoretical significance and practical application value.
To study the influence and mechanism of this paper mainly focuses on the amorphous alloy inoculant on casting Al-Cu alloy microstructure and strong plasticity of amorphous alloy. In order to reveal the effect of inoculation rule and its mechanism for grain refinement of as cast -Al Al-Cu alloy; amorphous alloy with different resistance mechanism of inoculation and amorphous alloy casting recession inoculation on Al-Cu alloy at room temperature. High temperature and strong plastic effect rule and mechanism. The main results of this paper are as follows:
1) found that ZrCuAlNi, ZrCuAlNiLa, FeBSi and NiNbTi four kinds of amorphous alloy grain refinement of Al-Cu alloy -Al order from strong to weak ZrCuAlNi ZrCuAlNiLa amorphous amorphous amorphous amorphous NiNbTi FeBSi, their minimum size decreases the grain size of -Al were about 35m, 38m, 39m and 41m; the four amorphous effective incubation time from long to short order NiNbTi =FeBSi amorphous amorphous amorphous amorphous ZrCuAlNiLa ZrCuAlNi, effective incubation time they were 30min, 30min, 10min and 3min., in ZrCuAlNi amorphous alloy doped with rare earth element La can be effective incubation time of amorphous ZrCuAlNi increased from 3min to 10min.
2) revealed that the amorphous alloy has the Al-Cu alloy nano precipitates and without inoculation alloys' theta compared to size decreased significantly, the number increased significantly, more uniform distribution. The main mechanism for amorphous alloy modification of Al-Cu alloy grain refinement of the -Al, so that the grain length was significantly increased, the distribution of the second phase is conducive to the grain boundary of the alloy during solidification of the more uniform. And because the grain size is smaller, the solution treatment of second phase from grain boundary to intracrystalline diffusion distance decreases, so that a more uniform distribution of Cu atoms in the -Al matrix. The activation induced formation of nano precipitates' theta during aging can reduce the nano 'release of theta phase can be more easily at the same time, nucleation, precipitation, growth, caused by the lack of nano precipitates' theta required for the growth of Cu atoms, thus limiting the nano precipitates grow' theta theta ', make analysis The diameter and thickness of the phase are smaller.
3) found that the amorphous alloy Al-Cu alloy inoculation compared with non inoculation alloys at room temperature strength and ductility have been improved at the same time, the -Al grain size refinement of Al-Cu alloy strength and fracture strain increase rule and the amorphous alloys have the same rules. On the basis of breeding strength and plasticity enhance integrated principle, four kinds of non amorphous alloy modification of Al-Cu alloy with strong plasticity and improve from strong to weak law: (Zr55Cu30Al10Ni5) 97.2La2.8 alloy Zr55Cu30Al10Ni5 alloy Ni60Nb25Ti15 inoculation inoculation inoculation alloys Fe79.58B11.16Si9.26 inoculation alloys, their optimum strength and fracture strain were 536MPa and 16.3%, 569MPa and 11.1%, 531MPa and 14%, 520MPa and 14.2% respectively; inoculation alloys increased by 14% and 123%, 19.7% and 58.5%, 12.9% and 100%, 10.6% and 102%.
It is revealed that the main mechanism of increasing the strength of the amorphous Al-Cu alloy at the same time is the result of the common effect of grain refinement and the refinement of the precipitation phase of the nanoscale.
4) revealed for the first time ZrCuAlNi, ZrCuAlNiLa, FeBSi and NiNbTi four kinds of mechanism of amorphous alloy grain refinement of Al-Cu alloy -Al four amorphous alloy into Al-Cu alloy melt, crystallization, the formation of Zr2Cu, ZrCu (B2), Fe2B and NiTi phases. These phases can be used as heterogeneous nucleation of -Al the core, so that the -Al grain is obviously refined. The amorphous alloy is proposed as Al-Cu alloy inoculant criterion: the crystallization phase corresponding to meet -Al as core conditions.
5) revealed that FeBSi and NiNbTi amorphous amorphous ZrCuAlNi effective incubation time than effective inoculation causes of long time as -Al phase nuclei Fe2B and NiTi crystalline phase is higher than the melting point of Zr2Cu and ZrCu (B2) in non crystalline phase; ZrCuAlNi can effectively put the incubation time of ZrCuAlNi amorphous alloy increased from 3min to add 10min of rare earth element La crystal, which is mainly due to the rare earth La can improve -Al as heterogeneous nuclei of Zr2Cu and ZrCu (B2) high temperature stability of crystalline phase.
6) to develop long-term Al-Cu alloy amorphous alloy inoculant is the criterion for improving as the crystallization of -Al heterogeneous nucleation phase in Al-Cu alloy melt stability. The way is to improve the quality of different -Al as nucleation crystallization phase melting; or by alloying agent to the amorphous incubation, improve as the -Al phase nucleation crystallization phase stability at high temperature.
7) revealed no inoculation alloys, ZrCuAlNi and ZrCuAlNiLa amorphous alloy has the high temperature treatment of Al-Cu alloy deformation mechanism is dislocation climbing mechanism. We find that the temperature 433K~493K and strain rate range of 10-4~10-1s-1 Al-Cu alloy amorphous alloy inoculant in nano precipitation compared with no inoculation 'theta theta' nano alloy the small size, number and distribution. So the dislocation movement more difficult, the activation energy was significantly higher than that of non inoculation alloys deformation of Al-Cu alloy so that the amorphous alloy inoculant heat. Therefore, the ZrCuAlNi and ZrCuAlNiLa non high temperature amorphous alloy inoculation of the Al-Cu alloy is better than non pregnant Al-Cu alloy.
8) it is suggested that FeBSi amorphous alloy is a kind of inoculant with long inoculation time, good refining effect and low cost for refining Al-Cu alloy -Al grain.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG146.21

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