退火工艺对模具用高硬度ZAC合金组织与性能的影响  

Effect of annealing process on microstructure and properties of high-hardness ZAC alloy for molds

作　　者：祝一帆 陈明明 刘昕怡[1] 林高用[1,2] ZHU Yi-fan;CHEN Ming-ming;LIU Xin-yi;LIN Gao-yong(School of Materials Science and Engineering,Central South University,Changsha 410083,China;Key Laboratory of Nonferrous Metal Materials Science and Engineering Ministry of Education,Central South University,Changsha 410083,China)

机构地区：[1]中南大学材料科学与工程学院,湖南长沙410083 [2]中南大学有色金属材料科学与工程教育部重点实验室,湖南长沙410083

出　　处：《材料热处理学报》2022年第12期55-64,共10页Transactions of Materials and Heat Treatment

基　　金：湖南省自然科学基金资助项目(2020JJ4715)。

摘　　要：采用熔铸法制备了一种模具用高硬度Zn-Al-Cu(ZAC)合金,并探究了不同退火工艺对其组织演变及力学性能的影响。采用X射线衍射(XRD)、扫描电镜(SEM)、能谱仪(EDS)、室温拉伸/压缩试验和布氏硬度计等表征了合金的显微组织、拉伸断口形貌、微区成分和力学性能。结果表明:铸态ZAC合金的组织相结构复杂,包含初生β枝晶、层片状(η+β)/(η+α)共晶共析组织、沿晶ε(CuZn_(5))相和团聚状θ(CuAl_(2))相等;随着退火温度从290℃升高至380℃(退火时间为3 h)或保温时间从1 h延长至7 h(退火温度为320℃),合金中均匀分布的β相和ε相增多,合金组织由粗大枝晶及层片状组织转变为均匀细小的粒状组织,合金的布氏硬度和抗压强度先升后降,断后伸长率升高;退火过程中含铜ε相的增多及均匀化是合金获得高硬度、高强度且塑性不被削弱的主要原因。铸态ZAC合金经(320~350℃)×3 h退火后达到较佳的性能匹配,布氏硬度达158.80 HBW,抗压强度达918.55 MPa,断后伸长率达4.6%。A high-hardness Zn-Al-Cu(ZAC)alloy for molds was prepared by melt-casting method,and the effects of different annealing processes on its microstructure evolution and mechanical properties were investigated.Microstructure,tensile fracture morphology,micro area composition and mechanical properties of the alloy were characterized by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)analysis,room temperature tensile/compression test and Brinell hardness tester.The results show that the microstructure of the as cast ZAC alloy is complex,including primaryβdendrite,lamellar(η+β)/(η+α)eutectic eutectoid structure,intergranularε(CuZn_(5))phase and agglomeratedθ(CuAl_(2))phase.With the increase of annealing temperature from 290℃to 380℃(annealing time is 3 h)or holding time from 1 h to 7 h(annealing temperature is 320℃),the number of uniformly distributedβ-phase andε-phase of the alloy increases,the microstructure of the alloy changes from coarse dendrite and lamellar structure to uniform and fine granular structure,the Brinell hardness and compressive strength of the alloy increase first and then decrease,and the elongation increases.The increase and homogenization of copper-containingεphase during annealing process are the main reasons of the alloy for obtaining high hardness,high strength and no decrease in plasticity.After annealing at(320-350℃)for 3 h,the as cast ZAC alloy achieves a better performance match,the Brinell hardness reaches 158.80 HBW,the compressive strength reaches 918.55 MPa,and the elongation reaches 4.6%.

关 键 词：Zn-Al-Cu(ZAC)合金 模具 退火 高硬度 

分 类 号：TG146.1[一般工业技术—材料科学与工程]