Jung Sungsu, Park Yongho, Lee Youngcheol
Energy Component & Material R&BD Group, Korea Institute of Industrial Technology, Busan 46938, Republic of Korea.
Department of Materials Science and Engineering, Pusan National University, Busan 46241, Republic of Korea.
Materials (Basel). 2023 Jul 3;16(13):4799. doi: 10.3390/ma16134799.
The superheating process is a unique grain refining method found only in aluminum-containing magnesium alloys. It is a relatively simple method of controlling the temperature of the melt without adding a nucleating agent or refining agent for grain refinement. Although previous studies have been conducted on this process, the precise mechanism underlying this phenomenon has yet to be elucidated. In this study, a new approach was used to investigate the grain refinement mechanism of aluminum-containing magnesium alloys by the melting superheating process. AZ91 alloy, a representative Mg-Al alloy, was used in the study, and a rapid solidification process was designed to enable precise temperature control. Temperature control was successfully conducted in a unique way by measuring the temperature of the ceramic tube during the rapid solidification process. The presence of AlMn and AlMn particles in non-superheated and superheated AZ91 ribbon samples, respectively, manufactured by the rapid solidification process, was revealed. The role of these Al-Mn particles as nucleants in non-superheated and superheated samples was examined by employing STEM equipment. The crystallographic coherence between AlMn particles and magnesium was very poor, while AlMn particles showed better coherence than AlMn. We speculated that AlMn particles generated by the superheating process may act as nucleants for α-Mg grains; this was the main cause of the superheating grain refinement of the AZ91 alloy.
过热处理是一种仅在含铝镁合金中发现的独特的晶粒细化方法。它是一种相对简单的控制熔体温度的方法，无需添加形核剂或细化剂来细化晶粒。尽管此前已经对该过程进行了研究，但这一现象背后的确切机制仍有待阐明。在本研究中，采用了一种新方法来研究含铝镁合金通过熔体过热处理的晶粒细化机制。研究中使用了AZ91合金，一种典型的Mg-Al合金，并设计了快速凝固过程以实现精确的温度控制。通过在快速凝固过程中测量陶瓷管的温度，成功地以一种独特的方式进行了温度控制。揭示了通过快速凝固过程制造的未过热处理和过热处理的AZ91薄带样品中分别存在AlMn和AlMn颗粒。通过使用扫描透射电子显微镜设备研究了这些Al-Mn颗粒在未过热处理和过热处理样品中作为形核剂的作用。AlMn颗粒与镁之间的晶体学相干性很差，而AlMn颗粒显示出比AlMn更好的相干性。我们推测，过热处理产生的AlMn颗粒可能作为α-Mg晶粒的形核剂；这是AZ91合金过热处理晶粒细化的主要原因。
