熔剂中添加LaCl3对Mg合金显微组织与性能的影响

测试分析了含有不同量LaCl3的熔剂对Mg合金的力学性能、组织、断口形貌以及腐蚀行为的影响．结果表明，LaCl3以熔剂形式加入Mg合金中，合金内会形成粒状细小的Al10La2Mn7稀土相，该稀土相起到γ相形核核心的作用，使γ相得到细化．LaCl3可以提高合金的抗拉强度σb和延伸率δ当熔剂中含有5％的LaCl3时，σb和δ分别从161MPa和2．1％上升到最大值203MPa和4．2％．分别提高了26％和100％．之后，随着LaCl3加入量的进一步提高，在精炼过程中会造成熔剂结团，并增加Mg熔体内的夹杂，合金的力学性能反而下降．LaCl3不改变Mg合金的断裂机理，断口形貌仍为准解理断裂．研究还表明，含5％LaCl3的熔剂能明显改善Mg合金的耐蚀性，在5％Nacl溶液中腐蚀速率从1.10mg／(cm^2-d)下降到0．17mg／(cm^3-d)，降低了84％．

EFFECT OF LaCl3 ADDITION IN FLUX ON THE MICROSTRUCTURE AND PROPERTIES OF MAGNESIUM ALLOYS

The effects of the fluxes containing LaCl$_{3}$ on the mechanical properties, structure, fractography and corrosion behavior of magnesium alloy have been measured. The results show that small and nodular Al$_{10}$La$_{2}$Mn$_{7}$ phases can be formed in melts after fluxes containing LaCl$_{3}$ was added to Mg melt which can act as nucleating site of $\gamma$ phases, making the $\gamma$ phases refined. The tensile strength $\sigma_{\rm b}$ and elongation $\delta$ can be improved by addition of LaCl$_{3}$. Using fluxes containing 5\% LaCl$_{3}$, the $\sigma_{\rm b}$ and $\delta$ of the alloy can be improved from 161 MPa and 2.1\% to 203 MPa and 4.0\%, respectively. That is, the $\sigma_{\rm b}$ and $\delta$ increased by 26\% and 100\%, respectively. Increasing the content of LaCl$_{3}$ further, the fluxes will agglomerate during the refinement process, so that the inclusions in the melt will increase and the mechanical properties of Mg alloys decrease. The fracture mechanism of quasincleavage of Mg alloy has not been changed by LaCl$_{3}$, The corrosion test results show that LaCl$_{3}$ can improve obviously the corrosion resistance of Mg alloy. The corrosion rate of magnesium alloys can decrease from 1.10 mg/(cm$^{2}\cdot$d) to 0.17 mg/(cm$^{2}\cdot$d) in 5\%NaCl solution by using fluxes containing 5\% LaCl$_{3}$. That is, the corrosion rate can be decreased by 84\%.