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以Al,K2ZrF6和KBF4为原料,采用熔体反应法制备不同B/Zr摩尔比Al-Zr-B合金。利用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射分析(XRD)等手段研究了B/Zr摩尔比对Al-Zr-B中间合金的组织和晶粒细化效果的影响。结果表明,随着B/Zr摩尔比的增加,Al-Zr-B中间合金的第二相组成发生改变。当B/Zr摩尔比为1时,第二相主要由粗大的块状ZrAl3相及少量团聚在晶界上的ZrB2粒子组成;当B/Zr摩尔比为2时,第二相为ZrB2粒子和少量块状ZrAl3相。当B/Zr摩尔比为3时,第二相全部为ZrB2粒子。对AZ91D合金的细化实验表明,随着B/Zr摩尔比的增加,晶粒细化效果越好,添加B/Zr摩尔比为3的Al-Zr-B中间合金具有明显的细化效果,合金由粗大的树枝晶转变成细小的等轴晶,固溶处理后的AZ91D合金平均晶粒尺寸由约328μm下降到约120μm;抗拉强度和延伸率达到213 MPa和4.95%,比未添加细化剂时分别提高了15.1%和30.3%。晶粒细化机制可归结为ZrB2粒子作为α-Mg的异质形核核心。
Using Al, K2ZrF6 and KBF4 as raw materials, different B / Zr molar ratio Al-Zr-B alloys were prepared by melt reaction. The effect of B / Zr molar ratio on microstructure and grain refinement of Al-Zr-B master alloy was investigated by OM, SEM and XRD. The results show that with the increase of B / Zr molar ratio, the second phase composition of Al-Zr-B master alloy changes. When the B / Zr molar ratio is 1, the second phase mainly consists of coarse bulk ZrAl3 phase and a small amount of ZrB2 particles agglomerated on the grain boundaries. When the B / Zr molar ratio is 2, the second phase is ZrB2 particles and A small amount of massive ZrAl3 phase. When the B / Zr molar ratio is 3, the second phase is all ZrB2 particles. The refinement experiments of AZ91D alloy show that the grain refining effect is better with the increase of B / Zr molar ratio, and the refining effect of Al-Zr-B master alloy with B / Zr molar ratio of 3 is obvious. The alloy transformed from coarse dendrites to fine equiaxed grains. The average grain size of solution treated AZ91D alloy decreased from about 328μm to about 120μm. The tensile strength and elongation reached 213 MPa and 4.95%, respectively, Chemical agents were increased by 15.1% and 30.3%. The grain refinement mechanism can be attributed to ZrB2 particles as heterogeneous nucleation sites of α-Mg.