钠对铝铜合金的有害作用及无钠精炼剂的研制

发布时间：2018-06-03 03:01

  本文选题：钠 + 铝铜合金　； 参考：《山东大学》2015年硕士论文

【摘要】：铝及铝合金在国民经济和国防建设各领域中起着相当重要的作用。ZL205A是由我国研制并开发的高强度铸造铝合金,其广泛应用于我国的航空航天行业。对于铝及其合金制品,含氢量和夹杂物(A1203)等冶金缺陷的存在会直接或间接影响其机械性能或使用性能。所以,要想获得高质量的产品,必须在浇铸前想办法消除这些冶金缺陷,从而提高熔体的纯净度水平。使用精炼剂是提高铝熔体纯净度水平的有效方法。对于铝合金的精炼剂,市场上以含钠精炼剂为主。对于使用ZL205A的军工企业,他们发现使用含钠的精炼剂后对合金的性能造成了不利的影响。为了研究并解决这一工业问题,我们在本论文中研究了钠在铝铜合金中的存在形式和位置以及对合金性能的影响,另外我们还开发了无钠精炼剂。本文以含钠精炼剂为介质向铝铜合金中引入钠,利用扫描电子显微镜(SEM)、探针X射线显微分析仪(EPMA)、X射线衍射仪(XRD)、高分辨透射电镜(HRTEM)等分析手段分析了钠在铝铜合金中的存在形式以及存在位置。同时也研究了Na的加入对合金产生了哪些不利的影响。本文还配制了多种无钠精炼剂,然后通过DSC实验确定各个配方的熔点,利用减压凝固的方法来确定其除气除杂的效果,最后在生产实验条件下配合旋转喷吹精炼机来确定配方是否合适。最终获得了一种专用于铝铜合金的无钠精炼剂。本文的主要研究工作如下：(1)通过熔剂将Na加入到Al-4.5 wt.% Cu合金里。在电子探针显微镜(EPMA)下发现晶界有Na的存在,高分辨透射电镜(HRTEM)下观察到了低熔点物质的溶解,结合这两点,推定加入的Na存在于A1-4.5wt.%Cu晶界上,并且是以单质钠呈薄膜态富集于晶界上。这种Na减弱了a-A1相与CuAl2相之间的结合力,使得Al-4.5 wt.% Cu合金中的CuAl2相在样品制作过程中易脱落。(2)加入Na的Al-4.5 wt.% Cu在T6时效后产生裂纹,裂纹处有Na的富集。在T6时效过程中,存在于晶界的单质钠熔化,成为裂纹源,在时效过程中扩展生长,最终形成裂纹。在固溶过程中,因为薄膜层的液态钠的存在,使得a-Al相与CuAl2相的互溶速度减慢,这就导致了时效后CuAl2目的残留。这种残留的CuAl2相在制样过程中也易脱落。(3)T6时效后含Na的Al-4.5 wt.% Cu性能急剧下降,断面的扫描显微镜照片显示,Al-4.5 wt.% Cu的断裂方式由韧窝断裂变为了沿晶断裂。(4)所选取的配置精炼剂D的起始熔点为703.9℃,减压凝固试验后的截面气孔率低于1%,配合旋转喷吹精炼机使用后合金性能有所提高。
[Abstract]:Aluminum and aluminum alloys play a very important role in the national economy and national defense construction. ZL205A is a high strength cast aluminum alloy developed by our country. It is widely used in the aerospace industry of our country. For aluminum and its alloy products, the presence of metallurgical defects such as hydrogen content and inclusion A1203 will directly or indirectly affect their mechanical or operational properties. Therefore, in order to obtain high quality products, we must find a way to eliminate these metallurgical defects before casting, so as to improve the purity level of melt. The use of refining agent is an effective method to improve the purity of aluminum melt. For aluminum alloy refining agent, the market mainly contains sodium refining agent. For military companies using ZL205A, they found that the use of sodium-containing refiners adversely affected the properties of the alloy. In order to study and solve this industrial problem, we have studied the form and position of sodium in Al-Cu alloy and its influence on the properties of Al-Cu alloy in this thesis. In addition, we have developed a non-sodium refining agent. In this paper, sodium was introduced into Al-Cu alloy in the medium of refining agent containing sodium. The existence and location of sodium in Al-Cu alloy were analyzed by means of scanning electron microscope (SEM), probe X-ray microanalyzer (EPMA), X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM). At the same time, the negative effects of Na addition on the alloy were also studied. In this paper, several kinds of sodium free refining agents were prepared, and the melting point of each formula was determined by DSC experiment, and the effect of removing gas and impurity was determined by the method of vacuum solidification. Finally, the formula is determined by rotating injection refining machine under the condition of production experiment. Finally, a sodium-free refining agent for Al-Cu alloy was obtained. The main work of this paper is as follows: 1) adding Na into Al-4.5 wt.% Cu alloy by flux. The presence of Na at grain boundary was observed under EPMA, and the dissolution of low melting point material was observed under high resolution transmission electron microscopy (HRTEM). Combined with these two points, Na was presumed to exist at the grain boundary of A1-4.5wt.%Cu. And it is enriched on grain boundary in the thin film state of sodium. This kind of Na weakens the binding force between a-A1 phase and CuAl2 phase, which makes the CuAl2 phase in Al-4.5 wt.% Cu alloy fall off easily during sample making.) the Al-4.5 wt.% Cu of Na is added into Al-4.5 wt.% Cu to produce cracks after T6 aging, and there is Na enrichment in the crack. During the aging process of T6, the elemental sodium existing at grain boundary melts and becomes the source of crack, which propagates and grows in the aging process, and finally forms the crack. Due to the presence of liquid sodium in the film layer, the intersolubility rate of a-Al phase and CuAl2 phase is slowed down during the solution process, which leads to the residual of CuAl2 after aging. The residual CuAl2 phase is easy to fall off during the preparation of the sample, and the properties of Al-4.5 wt.% Cu containing Na decrease sharply after aging. The scanning microscope photos of the section show that the fracture mode of Al-4.5 wt.% Cu changed from dimple fracture to intergranular fracture. 4) the initial melting point of the modified refining agent D is 703.9 鈩，

本文编号：1971211