Kim Min Gyu, Kim Woo Jin, Kim Gyeung-Ho, Cho Kwon-Koo, Han Jun Hyun, Kim Hye Sung
Departmemt of Nanofusion Technology, Pusan National University, 50 Cheonghak-ri, Samnangjin-eup, Miryang-si, Kyongnam 627-706, Korea.
Department of Materials Science and Engineering, Hongik University, 72-1 Mapo-gu, Sangsu-dong, Seoul 121-791, Republic of Korea.
J Nanosci Nanotechnol. 2018 Sep 1;18(9):6081-6089. doi: 10.1166/jnn.2018.15609.
The microstructure and corrosion properties of as-cast AZ61 (Mg-6%Al-1%Zn) and AZ61 alloys doped with titanium and calcium and subjected to high ratio differential speed rolling were investigated. Addition of the alloying elements to the AZ61 alloy resulted in remarkable modification of the morphology and the amount of continuous β (Mg17Al12)-phase. Addition of Ti to the as-cast AZ61 alloy causes a decrease in the volume fraction (or discontinuity of the β-phase), leading to strong anodic dissolution. In contrast, addition of Ca to the as-cast AZ61 alloy is rather effective for preventing pitting corrosion. This is attributed to the formation of a semi-continuous network β-structure. The (Mg, Al)4Ca phases dispersed between the β (Mg17Al12)-phases led to continuity in the AZ61 alloy with Ca. The AZ61 and AZ61-X(Ca, Ti) alloys subjected to severe plastic deformation via high-ratio differential speed rolling possessed a nano-composite-like microstructure in which the α-Mg matrix with an ultra-fine grain was surrounded by a large number of fine β particles. These particles were either dynamically precipitated or broken at the grain boundaries, as well as in the grain interiors, by the high ratio differential speed rolling process. The corrosion resistance of the AZ61 and AZ61-X (X = Ca, Ti) alloys subjected to high ratio differential speed rolling was largely improved by the microstructural modification. The high ratio differential speed rolling process greatly influenced the texture of the Mg alloys, which significantly affected their corrosion behavior.
研究了铸态AZ61（Mg-6%Al-1%Zn）以及掺杂钛和钙并经过高比例差速轧制的AZ61合金的微观结构和腐蚀性能。向AZ61合金中添加合金元素导致连续β（Mg17Al12）相的形态和数量发生显著变化。向铸态AZ61合金中添加Ti会导致β相的体积分数降低（或β相的连续性降低），从而导致强烈的阳极溶解。相比之下，向铸态AZ61合金中添加Ca对于防止点蚀相当有效。这归因于形成了半连续网络β结构。分散在β（Mg17Al12）相之间的（Mg，Al）4Ca相使得含Ca的AZ61合金具有连续性。通过高比例差速轧制进行严重塑性变形的AZ61和AZ61-X（Ca，Ti）合金具有类似纳米复合材料的微观结构，其中具有超细晶粒的α-Mg基体被大量细小的β颗粒包围。这些颗粒通过高比例差速轧制过程在晶界以及晶粒内部动态析出或破碎。微观结构的改变极大地提高了经过高比例差速轧制的AZ61和AZ61-X（X = Ca，Ti）合金的耐腐蚀性。高比例差速轧制过程对镁合金的织构有很大影响，这显著影响了它们的腐蚀行为。
