高温挤压诱导纳米α-Mn相动态析出协同提升Mg-Zn-Mn-Gd-Ca合金强度与耐蚀性

High-Temperature Extrusion-Induced Dynamic Precipitation of Nano-Sized α-Mn Phase Synergistically Enhances the Strength and Corrosion Resistance of Mg-Zn-Mn-Gd-Ca Alloy

摘要:

为解决镁合金强度和耐腐蚀性难以协同提升问题，通过扫描电子显微镜、透射电子显微镜、电子背散射衍射、开尔文探针力显微镜、拉伸实验、浸泡实验和电化学实验，研究了挤压温度（360 ℃和380 ℃）对Mg-2Zn-0.8Mn-0.7Gd-0.3Ca合金微观组织、力学性能和腐蚀行为的影响。结果表明：提高挤压温度至380 ℃最主要微观影响是显著促进α-Mn纳米粒子的动态析出；该析出相钉扎晶界，抑制晶粒长大；通过第二相强化和细晶强化共同作用，合金屈服强度由202 MPa提升至244 MPa；同时，合金在3.5 wt% NaCl中浸泡稳定后的膜层电阻由2238 ohm cm2提升至4811 ohm cm2，腐蚀速率由1.325 mm·y-1降至0.839 mm·y-1，膜层防护性提升可能与弥散纳米α-Mn粒子析出相关。本研究通过简单改变热挤压工艺，实现了强度与耐蚀性的同时提升，为高强耐蚀镁合金设计提供新视角。

Abstract:

To address the challenge of synergistically improving the strength and corrosion resistance of magnesium alloys, the effects of extrusion temperatures (360 °C and 380 °C) on the microstructure, mechanical properties, and corrosion behavior of the Mg-2Zn-0.8Mn-0.7Gd-0.3Ca alloy were systematically investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscattered diffraction (EBSD), scanning Kelvin probe force microscopy (SKPFM), tensile tests, immersion tests, and electrochemical measurements. The results show that the most significant microstructural effect of increasing the extrusion temperature to 380 °C is the remarkable promotion of dynamic precipitation of α-Mn nanoparticles. These precipitated phases pin the grain boundaries and inhibit grain growth. Through the combined effects of second-phase strengthening and grain refinement strengthening, the yield strength of the alloy is increased from 202 MPa to 244 MPa. Meanwhile, after stable immersion in 3.5 wt% NaCl solution, the surface film resistance of the alloy is enhanced from 2238 ohm cm2 to 4811 ohm cm2, and the corrosion rate is reduced from 1.325 mm·y-1 to 0.839 mm·y-1. The improved protective performance of the film may be associated with the precipitation of dispersed nano-sized α-Mn particles. By simply adjusting the hot extrusion process, this study achieves the simultaneous enhancement of strength and corrosion resistance, providing a new perspective for the design of high-strength and corrosion-resistant magnesium alloys.