稀土Nd对ZM5合金组织与性能影响的研究

Effects of RE Element Y on the Microstructure of ZM5 Mg Alloy

在ZM5合金熔体中加入不同量的稀土Nd,经过不同处理,利用光学显微镜、扫描电镜以及能谱分析,研究了稀土Nd对ZM5合金组织的影响规律。试验结果表明,向ZM5合金中添加稀土Nd的质量分数达2%时,合金的显微组织明显改善。X衍射和金相照片显示ZM5合金铸态组织为α-Mg固溶体和沿晶界分布的网状β-Mg17Al12组成,固溶处理后Mg17Al12弥散在基体中,而加入稀土元素Nd的ZM5合金由α(基体),Mg17Al12,颗粒状Mg12Nd等相组成。经固溶处理后网状Mg17Al12相完全溶解,留下热稳定较高的析出相Mg12Nd等。扫描电镜显示ZM5合金拉伸试样断口是解理断裂的断口形态,而加入稀土Nd的ZM5合金拉伸试样断口是沿晶断裂+准解理断裂的混合断口形态。其原因是加入稀土Nd后,熔体中生成了与镁基体共格的强化相Mg12Nd改变了其断口形貌。

The effects of different Y contents on microstructure of ZM5 Mg alloy were investigated by optical microscope and SEM and EPA.It was found that 2[WTXT]%[WT] Y addition can obviously improve the microstructure of the ZM5 Mg alloy.X ray diffusion and OM observation indicated as-cast microstructure of the alloy consitsts of α-Mg phase and net-like β-Mg_(12)Al_(17) phase in boundary,in which solid solution treated β-Mg_(12)Al_(17) phase was dispersed in the matrix,in turn,microstructure of ZM5 alloy containing Re element Y consists of α phase,β-Mg_(12)Al_(17) phase and particle MgY phase.Solid solution treated alloy consists of MgY phase and precipitated Al_2Y phase.SEM showed that ZM5 Mg alloy possesses the features of cleavage fracture while ZM5 Mg alloy containing Y has mixed fracture morphology of quasi-cleavage fracture and boundary fracture.The reason is that enhancing phase MgY and dispersely precipitated phase transform the fracture morphology.