钇在AZ91D镁合金熔体中合金化技术的研究

Research on Alloying Technique of Yttrium in AZ91D Magnesium Alloy

为了提高稀土钇在镁合金中的收得率并改善稀土镁合金的组织,采用扫描电镜、XRD、光学显微镜、ICP光谱仪,研究了直接添加金属钇和添加铸态及挤压态Mg-Y中间合金对镁合金组织及稀土钇收得率的影响。结果显示:用井式坩埚炉熔炼镁合金AZ91D,直接添加Y时,在熔炼温度750℃、60 min内收得率低于50%而且未完全熔解。生成的Al-Y金属间化合物组织粗大,并容易沉降到熔体底部。以铸态及挤压态Mg-Y中间合金加入时,生成的Al-Y金属间化合物组织细小均匀,Y收得率分别为71.3%和78.3%;以铸态中间合金加入时收得率略低于以挤压态中间合金加入时的收得率。其原因是中间合金中的α-Mg基体首先溶解,Mg_(24)Y_5相随之分散到熔体并分解为Mg_2Y;经挤压变形后,Mg_(24)Y_5相被破碎成更为细小的颗粒,加入合金熔体后分解为Mg_2Y,粒径越小沉降速度越缓慢,提高了Y的收得率。

In order to improve the absorptivity of rare earth yttrium in magnesium alloy and the microstructure of rare earth magnesium alloy, the effects of adding yttrium metal directly, addition of as cast and extruded Mg-Y master alloy on the microstructure of AZ91D and the absorptivity of rare earth yttrium were studied by means of scanning electron microscopy, XRD, optical microscopy and inductively coupled plasma spectroscopy. The results show that with well type crucible furnace melting AZ91D and adding yttrium directly, the absorptivity is less than 50%, and the yttrium is not completely melting in the melting temperature of 750 ℃ for 60 min. Formation of A1-Y intermetallic compound is coarse and easy to sink to the bottom of the melt. When yttrium is added as cast and extruded Mg-Y master alloy, the yttrium absorptivity is 71.3% and 78.3% respectively. The absorptivity of as cast alloy addition is slightly lower than that of extruded master alloy addition. The ot-Mg in the master alloy dissolves firstly, and Mg24Y5 disperses into the melt and decomposes into Mg2Y. The Mg24Y5 phase is broken into small particles after extrusion, and it decomposes into Mg2Y in the melt.The smaller the particle size, the slower the settling velocity, and the absorptivity ofyttrinm is increased.