金属表面参数及时效对润湿性的影响规律研究
发布时间：2019-06-05 06:01
【摘要】：金属材料的形核一般与过冷度有着密切的联系,保证一定的过冷度需要使模具材料具有很好的传热性能,但是由于气体裹陷现象的存在,使金属液与模壁之间夹杂了一部分空气,导致金属液的传热性能变差,使金属的异质形核受到影响。气体裹陷存在的原因主要是由于模具表面存在一定的微观粗糙度,当金属液与模具表面接触时,凹槽部分被密封了空气,形成了Cassie润湿模型所述的现象,阻碍金属液与模具表面的接触,降低了金属液冷却过程中对外界的传热效率,同时,这种金属液与模壁形成润湿体系,因此可以发现金属材料表面的润湿性对于金属形核起着举足轻重的作用。本文以金属液的异质形核为出发点,结合杨氏方程、Wenzel模型理论与Cassie模型理论,以水为介质研究金属表面的润湿性。实验的第一部分主要采用易于制备试样的纯铝和高纯铝材料,通过化学刻蚀的方法制备具有亲水性的表面,并在室温下进行时效,分析润湿性随时效时间的变化规律。实验以2mol/L浓度的盐酸进行刻蚀,将试样分别刻蚀4min到20min,清洗并吹干制备好的试样,利用OCA15EC接触角测量仪进行润湿角测定,然后将试样放置在室温下进行时效,并记录时效后的润湿角,分析润湿角的变化规律;采用扫描电子显微镜观察试样表面的微观形貌,结合Wenzel理论与Cassie理论分析润湿角变化的原因;对试样做EDS分析,分析时效后试样所含元素含量的变化情况,阐述润湿性变化的机理。第二部分将制备好的试样在高温炉中进行200℃,300℃和400℃高温时效,时效时间均为1h,记录时效前后的润湿角度,分析润湿角的变化规律;观察试样表面的微观形貌,分析EDS中的元素变化情况,阐述润湿性变化的机理。最终得出不同的刻蚀时间制备的试样润湿角存在差异,刻蚀时间为16min的纯铝能够获得比较稳定的表面形貌,高纯铝材料在进行12min的刻蚀即可得到稳定的润湿性,试样的润湿角维持在12°以下,且形貌较好。高温时效后发现,不同的刻蚀时间制备的试样经过高温时效润湿角存在差异,在200℃高温下时效1h导致润湿角急剧变大,300℃下时效1h润湿角开始变小,当进行400℃时效1h后试样变为超亲水。为了使研究更为充分,利用化学刻蚀法在抗腐蚀能力强的不锈钢上制备亲水表面,因此第三部分以304不锈钢为基体材料,以化学刻蚀为制备方法,研究室温下与高温时效后的润湿角变化情况,发现室温时效后的润湿角变化规律及高温时效后的润湿角规律与铝基材料的润湿角变化规律有相似性,但是由于不同金属之间的元素亲水性不同,两者之间存在着一定的差异。因此,该论文对于进一步研究高温下金属液凝固过程中的润湿性有着重要的意义。
[Abstract]:The nucleation of metal materials is generally closely related to the undercooling degree. To ensure a certain undercooling degree, the mold materials need to have good heat transfer performance, but due to the existence of gas entrapment phenomenon, A part of air is mixed between the liquid metal and the die wall, which leads to the poor heat transfer performance of the liquid metal and affects the heterogeneous nucleation of the metal. The reason for the existence of gas entrapment is mainly due to the existence of a certain degree of microroughness on the surface of the die. When the liquid metal is in contact with the surface of the die, the groove part is sealed with air, forming the phenomenon described in the Cassie wetting model. Hinders the contact between the liquid metal and the surface of the die, reduces the heat transfer efficiency to the outside world in the cooling process of the liquid metal, and forms a wetting system between the liquid metal and the wall of the die. Therefore, it can be found that the wettability of metal material surface plays an important role in metal nucleation. In this paper, based on the heterogeneous nucleation of liquid metal, combined with Yang's equation, Wenzel model theory and Cassie model theory, the wettability of metal surface is studied with water as medium. In the first part of the experiment, pure aluminum and high purity aluminum materials which are easy to prepare samples are used to prepare hydrophilic surfaces by chemical etching. the hydrophilic surfaces are aged at room temperature, and the variation of wettability with aging time is analyzed. The samples were etched with hydrochloric acid of 2mol/L concentration for 20 min, and the samples were cleaned and dried. The wetting angle was measured by OCA15EC contact angle measuring instrument, and then the samples were aged at room temperature. The wetting angle after aging was recorded and the change law of wetting angle was analyzed. Scanning electron microscope (SEM) was used to observe the microstructure of the sample surface, and Wenzel theory and Cassie theory were used to analyze the reasons for the change of wetting angle. The EDS analysis of the sample was carried out, the change of element content in the sample after aging was analyzed, and the mechanism of wettability change was expounded. In the second part, the prepared samples were aged at 200 鈩，
本文编号：2493308
[Abstract]:The nucleation of metal materials is generally closely related to the undercooling degree. To ensure a certain undercooling degree, the mold materials need to have good heat transfer performance, but due to the existence of gas entrapment phenomenon, A part of air is mixed between the liquid metal and the die wall, which leads to the poor heat transfer performance of the liquid metal and affects the heterogeneous nucleation of the metal. The reason for the existence of gas entrapment is mainly due to the existence of a certain degree of microroughness on the surface of the die. When the liquid metal is in contact with the surface of the die, the groove part is sealed with air, forming the phenomenon described in the Cassie wetting model. Hinders the contact between the liquid metal and the surface of the die, reduces the heat transfer efficiency to the outside world in the cooling process of the liquid metal, and forms a wetting system between the liquid metal and the wall of the die. Therefore, it can be found that the wettability of metal material surface plays an important role in metal nucleation. In this paper, based on the heterogeneous nucleation of liquid metal, combined with Yang's equation, Wenzel model theory and Cassie model theory, the wettability of metal surface is studied with water as medium. In the first part of the experiment, pure aluminum and high purity aluminum materials which are easy to prepare samples are used to prepare hydrophilic surfaces by chemical etching. the hydrophilic surfaces are aged at room temperature, and the variation of wettability with aging time is analyzed. The samples were etched with hydrochloric acid of 2mol/L concentration for 20 min, and the samples were cleaned and dried. The wetting angle was measured by OCA15EC contact angle measuring instrument, and then the samples were aged at room temperature. The wetting angle after aging was recorded and the change law of wetting angle was analyzed. Scanning electron microscope (SEM) was used to observe the microstructure of the sample surface, and Wenzel theory and Cassie theory were used to analyze the reasons for the change of wetting angle. The EDS analysis of the sample was carried out, the change of element content in the sample after aging was analyzed, and the mechanism of wettability change was expounded. In the second part, the prepared samples were aged at 200 鈩，
本文编号：2493308
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