标题: | 升温速率与持温时间对超细晶粒AZ80镁合金半固态显微结构之影响 Study on the effect of heating rate and holding time on the microstructure of ultra-fine grain magnesium in the semi-solid state |
作者: | 曹植培 Chou, Chek-Pui 徐瑞坤 Hsu, Ray-Quen 机械工程学系 |
关键字: | 镁合金;半固态成形;升温速率;持温时间;Magnesium;Semi-Solid forming;heating rate;holding time |
公开日期: | 2012 |
摘要: | 镁合金具有质轻、比强度高等优点,但在室温下其成形性不佳,以致它在应用上不如铝合金广泛。半固态成形是在固液相共存时进行加工的成形技术,比起传统铸造法,半固态成形可制作出机械性质良好的工件,适合应用于镁合金。 半固态铸造/锻造是半固态成形技术中成本相对较低的成形方法,此方法需要先准备具有球状晶的胚料,再把胚料升温到半固态温度进行加工成形;而大量塑性变形法中的等径转角挤制法能产生超细晶粒,此超细晶粒材料在升温到半固态后会得到尺寸较小之球状晶,适合作为半固态成形之胚料。 本研究主要探讨半固态加工温度、升温速率与持温时间对超细晶粒镁合金半固态显微组织与机械性质之影响。利用高周波感应加热实现对材料快速升温,观察材料在加热与半固态持温过程中显微组织变化;并且利用压缩试验,比较经过等径转角挤制的超细晶粒材料与原素材在成形性上的差异。 实验结果显示半固态加工温度对晶粒尺寸有重大影响;较快的升温速率、较小的晶粒尺寸以及较好的圆球化效果都有助于半固态成形;而经过等径转角挤制的材料,可以缩短半固态成形的持温时间。 Magnesium alloy has many advantages, such as light weight, high specific strength, but its formability is limited under room temperature, so that it is not used widely as aluminum alloy. Semi-solid forging and casting is a low cost process that can be used in magnesium forming, it can make good products, this process need the billets that have spherical grains while they are heated to semi-solid temperature for forming. In this study, the microstructure evolution influenced by holding temperature, heating rate and holding time were studied, ultra-fine grain AZ80 produced by ECAE (Equal Channel Angular Extrusion) was compare with As Extrude AZ80 in semi-solid state. In this study, we used the high frequency induction heating to provide a fast heating rate. And observe the microstructure evolution in the heating and temperature holding process after quenching. The result showed that holding temperature had great effect on grain size in semi-solid state; smaller grain size and more circular spherical grain shape were benefit for semi-solid forming. ECAE AZ80 was a better choice for semi-solid forming than As Extrude AZ80 as billet material. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079914615 http://hdl.handle.net/11536/49501 |
显示于类别: | Thesis |
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