稀土Ho对AZ61合金显微组织及力学性能的影响

Effect of Ho on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy

采用OM、XRD、SEM、EDS和高温拉伸试验机研究了不同Ho含量对AZ61合金的微观组织与力学性能的影响。结果表明,加入Ho能够细化基体组织,使β-Mg17Al12相由连续的网状变为断续的岛状和鱼骨状,但是加入量超过1.0%时,β相有重新结网的倾向,同时基体也有粗化的趋势。同时从基体中逐渐析出花瓣状的相,可以判断该相为Al-Mn-Ho的三元相。Ho的加入促进Al-Mn相的析出从而转化为三元相,随Ho的加入该相逐渐增多,并均匀分布在基体中和晶界处。同时随着Ho含量的增加,常温和高温下的力学性能都有了一定的改善。分析可知合金的抗拉强度σb、延伸率δ和韧性都在加入Ho量为1.0%时达到最大值分别为207.88 MPa、13.22%、11.5 J/cm2。当Ho含量为1.5%时合金的硬度达到了峰值为68.9 HB。当Ho加入量为1.0%时高温性能效果最佳,强度和延伸率分别为128 MPa、13.2%.

In this paper,the effects of Ho on microstructure and mechanical properties of AZ61 magnesium alloy have been investigated by using X-ray diffraction（XRD）,optical microscopy（OM）,and scanning electron microscopy（SEM）,energy dispersive spectroscopy （EDS）and various testing machines.The results indicate that the addition of Ho suppresses the formation of β-Mg17Al12 phase and modifies the β-Mg17Al12 phase.When the addition of Ho is more than 1.0% ,coarsening trend appears in the β-Mg17Al12 and the matrix phase.Furthermore,new phases are formed in the forms of petal-like shape,which are verified as A1-Mn-Ho phase.The precipitates gradually distributed within the grain boundaries uniformly.Meanwhile,with the increasing Ho addition to AZ61 ,the mechanical properties of AZ61 two experimental alloys have been significantly improved in room and elevated temperature.Analysis shows that with the addition of 1.0% Ho,the maximum ultimate tensile strength and elongation percentage and toughness are obtained.Their values were 207.88 MPa,13.22% ,11.5 J/cm2 at room temperature and 128 MPa, 13.2% at elevated temperature, respectively.The maximum hardness of AZ61 alloy was obtained when adding 1.5% Ho.The value was 68.9 HB.