镁基准晶对AZ91合金组织与性能的影响

通过采用扫描电子显微镜、能量散射光谱和透射电镜等分析手段,研究了两种不同成分和形态的准晶中间合金对AZ91合金显微组织与力学性能的影响。结果表明,在AZ91合金中加入镁基准晶中间合金后,在其铸态合金的显微组织中除α-Mg基体相、β-Mg17Al12相外还出现了弥散分布在α-Mg内部和晶界附近的高热稳定的准晶相;由于加入的准晶中间合金中准晶相的形貌不同,遗传效应不同,所以其细化效果也存在差异。经准晶强化的AZ91合金常高温拉伸强度明显提高,但用MZYM中间合金对力学性能的提高要远远大于用MZY合金。这为镁基合金的强化提供一条新途经。

镁基准晶中间合金对AZ91组织和性能的影响

研究了镁基准晶中间合金和固溶处理工艺对AZ91合金显微组织和力学性能的影响。结果表明:随镁基准晶中间合金的加入AZ91的冲击韧性有显著的提高,当准晶中间合金增加到5.2%时,冲击韧性达到峰值,与基体合金相比提高了将近一倍;硬度也有提高。固溶处理(28 h)后,Mg17A l12相基本溶解,黑色的颗粒状准晶相在固溶处理过程中保持稳定而未溶解。固溶处理对合金的硬度影响不太明显。

镁基准晶强化AZ91合金的研究

研究了采用传统机械搅拌法制备含球形镁基准晶的AZ91镁合金,以及镁基准晶对AZ91镁合金的组织及性能影响。利用普通凝固技术,在Mg-Zn-Y系准晶中间合金中添加一定量的Ca或Mn元素,获得了含有球形二十面体准晶相的Mg-Zn-Y-Ca和Mg-Zn-Y-Mn准晶中间合金。结果表明:AZ91镁合金凝固结晶时形成粗大的树枝晶,β-Mg17Al12相呈网状分布于晶界,分别加入3.4%Mg-Zn-Y-Ca和5.2%Mg-Zn-Y-Mn后,合金的组织得到了很大的细化,β-Mg17Al12相以小块状弥散分布于晶界。同时合金的室、高温拉伸力学性能有很大幅度的提升。

Mn对Mg-Zn-Y合金中准晶相凝固组织形貌的影响

讨论了Mn对镁基准晶中间合金中三维二十面体球形准晶相形成过程的影响。研究表明:当在Mg-Zn-Y基准晶中间合金熔体中加入一定量的Mn元素后,在常规铸造条件下的结晶凝固过程中,完全可以改变Mg-Zn-Y基准晶中间合金中准晶的形成过程,获得稳定的均一二十面体初生Mg45Zn47Y5Mn3准晶相,避免了十面体准晶相的出现,改变了准晶相最终的形貌,由于Mn的加入,使初生准晶相的颗粒尺寸明显变小,使之由尺寸为60μm^80μm的花瓣状变成尺寸为≤20μm的球形状。Mn的加入,降低了镁基准晶中间合金的生产成本,为工业化生产提供了便利条件。

准晶增强Mg-Zn-RE合金的力学性能研究进展

主要介绍了准晶增强Mg-Zn-RE合金的常用制备方法,组织结构以及Mg-Zn-RE(Nd,Gd,Er,Y)等含准晶的镁基合金的常温和高温力学性能,最后对准晶增强MgZn-RE系的发展作了展望。

Effect of applied pressure on microstructure and mechanical properties of Mg-Zn-Y quasicrystal-reinforced AZ91D magnesium matrix composites prepared by squeeze casting

The Mg-Zn-Y quasicrystal-reinforced AZ91 D magnesium matrix composites were prepared by squeeze casting process. The effects of applied pressure on microstructure and mechanical properties of the composites were investigated. The results show that squeeze casting process is an effective method to refine the grain. The composites are mainly composed of α-Mg, β-Mg17Al12 and Mg3Zn6Y icosahedral quasicrystal phase（I-phase）. With the increase of applied pressure, the contents of β-Mg17Al12 phase and Mg3Zn6 Y quasicrystal particles increase, further matrix grain refinement occurs and coarse dendritic α-Mg transforms into equiaxed grain structure. The composite exhibits the maximum ultimate tensile strength and elongation of 194.3 MPa and 9.2% respectively when the applied pressure is 100 MPa, and a lot of dimples appear on the tensile fractography. Strengthening mechanisms of quasicrystal-reinforced AZ91 D magnesium matrix composites are chiefly fine-grain strengthening and quasicrystal particles strengthening.

Effect of Mg-based spherical quasicrystal on microstructures and mechanical properties of ZA54 alloy

To improve the strength, toughness and heat-resistance of magnesium alloy, the microstrucmre and mechanical properties of ZA54 alloy reinforced by icosahedral quasicrystal phase （/-phase） particles were studied. Except α-Mg, φ-phase and τ-phase, MgZnYMn I-phase particles can be obtained in ZA54-based composites by the addition of icosahedral quasicrystal-contained Mg-Zn-Y-Mn master alloy. The introduction of MgZnYMn I-phase into ZA54 alloy has great contribution to the refinement of matrix microstructures and the improvement of mechanical properties. When the addition of Mg-based spherical quasicrystal master alloy is up to 3.5% （mass fraction）, the macro-hardness of ZA54-based composites is increased to HB 68. The impact toughness of composites reaches the peak value of 18.3 J/cm^2, which is about 29% higher than that of ZA54 mother alloy. The highest tensile properties at ambient and elevated temperatures with master alloy addition of 2.5% （473 K） are also obtained in ZA54-based composites with 3.5% （mass fraction） Mg-Zn-Y-Mn master alloy addition. The ultimate tensile strength of composites at ambient and elevated temperatures are 192.5 MPa and 174 MPa, which are 23.4% and 33.8% higher than that of ZA54 mother alloy, respectively. The improved mechanical properties are mainly attributed to the pinning effect of I-phase on grain boundaries.