Effects of different cooling rates during two casting processes on the microstructures and mechanical properties of extruded Mg-Al-Ca-Mn alloy
Effects of different cooling rates during two casting processes on the microstructures and mechanical properties of extruded Mg-Al-Ca-Mn alloy
复制标题
DOI：
10.1016/j.msea.2012.02.034
复制
发表时间：
2012-04-30
期刊：
影响因子：
6.4
通讯作者：
Homma, T.
中科院分区：
文献类型：
--
作者：
Xu, S. W.;Oh-ishi, K.;Homma, T.
在本研究中，Mg-3.6Al-3.4Ca-0.3Mn（wt.%）通过具有不同冷却速率的两种铸造工艺制备了AXM 4303合金锭：具有10-20摄氏度/秒的较低冷却速率的永久模（PM）铸造和具有100-110摄氏度/秒的较高冷却速率的直接激冷（DC）铸造。然后，将这两种类型的AXM 4303合金锭在相同条件下在400摄氏度下热挤压。采用场发射扫描电镜（FE-SEM）、透射电镜（TEM）和电子背散射衍射（EBSD）系统研究了合金铸态和挤压态的微观组织。研究了铸造过程中不同冷却速度对AXM 4303合金挤压试样组织和力学性能的影响。结果表明，通过对挤压态Mg-Al-Ca-Mn合金的铸造过程进行组织控制，可以显著提高挤压态Mg-Al-Ca-Mn合金的强度。由于DC铸造工艺的冷却速率比PM铸造的冷却速率快得多，因此DC铸造AXM 4303具有以下性质：（i）层状共晶结构和枝晶晶胞尺寸显著细化，（ii）富含Al和Ca的有序单层GP区成核而不生长，以及（iii）大部分Mn保留在基体中的溶液中。因此，在热挤压之后，DC铸造的AXM 4303具有比挤压的PM铸造的AXM 4303中存在的更细的动态再结晶（DRX）晶粒尺寸、更细且更均匀分布的碎片状共晶颗粒、更细的平面Al 2Ca沉淀物和更细的球形Al-Mn沉淀物，其具有更高的数密度。结果，挤出DC铸造样品显示出409 MPa的拉伸0.2%屈服应力，其比挤出PM铸造样品的拉伸0.2%屈服应力大105 MPa。(C)2012 Elsevier B. V.保留所有权利。
In this study, Mg-3.6Al-3.4Ca-0.3Mn (wt.%) (which is denoted AXM4303) alloy ingots were prepared by two casting processes with different cooling rates: permanent mold (PM) casting, which has a lower cooling rate of 10-20 degrees C/s and direct chill (DC) casting, which has a higher cooling rate of 100-110 degrees C/s. Then, these two types of AXM4303 alloy ingots were hot extruded at 400 degrees C under the same conditions. The microstructures of the as-cast and extruded alloy samples were systematically investigated by field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) systems. The effects of the different cooling rates during the casting process on the microstructures and mechanical properties of the extruded AXM4303 alloy samples were evaluated. The results show that the strength of the extruded Mg-Al-Ca-Mn alloy can be substantially increased by microstructural control during the casting process. Because the cooling rate of the DC casting process is much faster than the cooling rate of PM casting, the DC-cast AXM4303 has the following properties: (i) the lamellar eutectic structure and dendrite cell size are significantly refined, (ii) the ordered monolayer GP zones enriched with Al and Ca nucleate with no growth, and (iii) most of the Mn remains in solution in the matrix. Thus, after hot extrusion, the DC-cast AXM4303 has finer dynamically recrystallized (DRXed) grain size, finer and more uniformly distributed fragmented eutectic particles, finer planar Al2Ca precipitates and finer spherical Al-Mn precipitates with higher number density than is present in the extruded PM-cast AXM4303. As a result, the extruded DC-cast sample showed a tensile 0.2% proof stress of 409 MPa, which is 105 MPa greater than that of the extruded PM-cast sample. (C) 2012 Elsevier B.V. All rights reserved.