Establishment of multi-scale structural controlling process technology aiming to high performance common magnesium alloys

我们的目标是通过对主要可热处理的普通Mg-Al-Ca-Mn合金应用多尺度显微组织控制来改善其机械性能。采用含有大量合金元素的Mg-Al-Ca-Mn合金直流铸造试样，在0.1mm·s-1的低速下，通过低温热挤压，获得了超高强度的普通镁合金。挤压试样的抗拉强度超过400 MPa，抗弯疲劳强度达到240 MPa，均优于超高强钢的上级水平。高强度是由于细颗粒Al-Ca化合物钉扎的细晶粒、纳米尺度的片状Al-Ca和球形Al-Mn-Ca析出相以及未再结晶区强的基面织构共同作用的结果，此外，采用晶界无结晶化合物的稀Mg-Al-Ca-Mn合金可以进行60 m/min的高速挤压。挤压速度与6063铝合金窗扇相当。在挤压试样的基体中，也通过挤压后的T5处理析出有序的GP区，导致拉伸性能几乎等于T5处理的6 N 01 Al合金，其实际上应用于新干线的双层蒙皮外板。

We aim to improve the mechanical properties by an application of multi-scale microstructural control to mainly heat treatable common Mg-Al-Ca-Mn alloys. Extraordinary high-strength common Mg alloy is obtained only by hot extrusion using a DC cast sample of the Mg-Al-Ca-Mn alloy with a large amount of alloying elements at low temperature under a low ram speed of 0.1 mm s-1. Namely, the extruded sample exhibits high tensile proof stresses more than 400MPa and rotational bending fatigue strength of240MPa whose values are superior to that of extra-super-duralmin. The high strengths are attributed to the combined results of fine DRXed grains pinned by finely fragmented Al-Ca compounds, nano-scale plate-like Al-Ca and spherical Al-Mn-Ca precipitates, and a strong basal texture at the unrecrystallized regions.Furthermore, we could carry out high speed extrusion of 60 m/min by using the dilute Mg-Al-Ca-Mn with no crystallized compounds at grain boundaries. The extrusion speed is comparable to that for 6063 Al window sash. In matrix of the extruded sample ordered GP zones also precipitate by T5 treatment after the extrusion, resulting in tensile properties being almost equal to T5-treated 6N01Al alloys, which are practically applied to a double skin outer panel of Shinkansen.