摘要
研究了不同的稀土含量(富Ce和Mg-Nd中间合金)对AZ61镁合金在热挤压变形过程中显微组织和力学性能的影响。结果表明,在加入1%～4%的混合稀土后,铸态AZ61镁合金组织中的β相明显减少,铸态组织晶粒得到细化,大部分的Ce,Nd与Al结合生成高熔点、高稳定性的稀土相Al4Ce或者Al4Ce和Al3Nd稀土混合相,并呈针状、棒状或者不规则块状分布于晶界或晶粒内部,同时各试验合金中均不同程度分布有不规则的块状α-Al8Mn5相;在热挤压过程中,Al4Ce或者Al4Ce和Al3Nd稀土混合相阻碍晶粒或亚晶粒长大,使晶粒较铸态组织变细,合金力学性能随稀土含量的增加有所提升,但由于稀土相较粗大,割裂晶界及晶粒间的结合力,使其性能大幅度下降;铸态AZ61+xRE各试验合金均为脆性断裂机制,挤压态AZ61合金断裂方式属于以韧性为主的韧脆混合断裂,含稀土挤压态合金中分布有塑性特征的韧窝,但主要以解理断裂为主。
Effects of different RE (rare earth) additions on the microstructure and mechanical properties of AZ61 alloys during hot deformation were investigated.With 1%～4% mischmetal addition,β-Mg17Al12 phase in as-cast microstructure of AZ61 magnesium alloy is greatly decreased,and grain size is obviously refined,and acicular,rod-like or irregular block Al4Ce phase or compound phase of Al4Ce and Al3Nd which is distributed into grain boundary or grain can be observed,meanwhile,irregular block α-Al8Mn5 phase can be observed in the experimental alloys too.During hot deformation process,Al4Ce phase or compound phase of Al4Ce and Al3Nd can refine microstructure of the alloy by inhibiting growth of grain or sub-grain,which slightly improves the mechanical properties of the alloy,however,compared with those of AZ61 matrix alloy,mechanical properties of the AZ61 alloy with RE addition are sharply deteriorated as a result of coarse RE phase dissevering grain boundary and binding force in grains.Fracture mechanism of as-cast AZ61+xRE alloy is characterized by brittle crack,and that of as-extruded AZ61 alloy is characterized by ductility-brittle crack,and that of as-extruded AZ61+xRE alloy is characterized by cleavage crack.
出处
《特种铸造及有色合金》
CAS
CSCD
北大核心
2010年第5期403-407,共5页
Special Casting & Nonferrous Alloys
基金
重庆市科技攻关项目(CSTC2007AA4008)
关键词
镁合金
稀土
热挤压
显微组织
力学性能
Magnesium Alloy,Rare Earth,Hot Extrusion,Microstructure,Mechanical Properties
