热处理对Mg-10Gd-2.5Nd-0.5Zr合金组织和耐蚀性能的影响

Influence of Heat Treatment on Microstructure and Corrosion Resistance of Mg-10Gd-2.5Nd-0.5Zr Alloy

通过OM,XRD,TEM和SEM等手段研究了热处理前后Mg-10Gd-2.5Nd-0.5Zr(质量分数,%)合金的显微组织形貌,并在3.5%(质量分数)Na Cl溶液中进行了0~96 h的失重腐蚀实验。结果表明:合金铸态组织由α-Mg基体和粗大的枝晶β相组成,热处理后,合金中的β相经溶解再析出过程,由断续网状转变为方块颗粒状;在3.5%Na Cl溶液中,经热处理后,合金的耐蚀性能明显提高,其平均腐蚀速率由铸态时的0.74 mg·cm^(-2)·d^(-1),降低到固溶态时的0.41 mg·cm^(-2)·d^(-1)和时效态时的0.35 mg·cm^(-2)·d^(-1),且腐蚀产物以Mg(OH)2为主。

The microstructure of Mg-10Gd-2.5Nd-0.5Zr（mass fraction, %） alloy after solid solution and aging treatment were characterized by means of OM, XRD, TEM and SEM. The average corrosion rate in 3.5%（mass fraction） Na Cl solution was measured for 0~96 h. The results show that the microstructure of the as-cast alloy is composed of α-Mg matrix and coarse dentritic crystal β phase.After heat treatment, the β phase has experienced a course of dissolution and then precipitation,while the discontinued net-like β-phase transformed into cuboid-shaped particles due to the solution and aging treatment. The heat treatments are beneficial to the corrosion resistant of the alloy in 3.5%Na Cl solution, while its corrosion rate was 0.74 mg·cm^（-2）·d^（-1）for the as-cast, 0.41 mg·cm^（-2）·d^（-1）for the solid solution treated and 0.35 mg·cm^（-2）·d^（-1）for the aging treated ones respectively. The corrosion products of the alloy is mainly composed of Mg（OH）2.