锆、钇微合金化对ZL205A合金组织性能的影响

Effect of Microscale Yttrium and Zirconium on Microstructure and Properties of ZL205 Alloy

稀土元素以其特有的性能而广泛被应用于微合金化领域。通过对ZL205A合金添加微量元素Y和Zr,采用OM,SEM和EDS等分析测试方法,研究不同含量的Y和Zr对铸态和T5热处理下ZL205A合金微观组织和力学性能的影响。结果表明:添加微量Y和Zr能提高合金的流动性,同时晶粒被明显细化,当添加量为0.1%(质量分数)(Zr 0.05%+Y 0.05%)时,流动性和晶粒被细化效果达到最佳状态,随着Y和Zr含量继续增加,对基体晶粒的细化效果减弱,晶间析出相增多,流动性提高的趋势降低,合金的充型能力下降,力学性能和延伸率呈下降趋势,合金表现为沿晶脆性和穿晶韧性的混合断裂方式;T5处理后,合金中部分微观偏析被消除,抗拉强度和硬度增大,但时效析出的θ″数量减少,弥散强化效果减弱,延伸率未得到改善。

The rare earth elements are widely used in the field of micro-Alloying with its unique properties. The microstructure and mechanical properties of the ZL205 alloy under as-cast and after T5 heat treatment with different contents of Y and Zr was studied through OM,SEM and EDS methods. The results showed that elements Zr and Y could improve fluidity of the alloy and grains were fined greatly. When the content of Y and Zr was 0. 1%（ Zr0. 05% ＋ Y 0. 05%）,the ability of fluidity improvement and fine grain degree was at their best status. With the increase of Y and Zr contents,the fine effect of the matrix grain was weakened. And intermetallic compounds stayed at grain boundaries were increased. At the same time,the increase trend of liquidity was limited,mold filling capacity decreased,the mechanical properties and elongation of the alloy drop and present ductile and brittle mix fracture mode. After T5 heat-treatment,partial micro segregation was eliminated,the tensile strength and hardness increased,while the content of θ″ phase reduced,dispersion strengthening effect on decreased and the elongation was not improved well.