Zn、Mg、Cu对7075铝合金热裂性能和组织的影响  

Influence of Zn,Mg and Cu Contents on Hot Cracking Behavior and Microstructure of 7075 Aluminum Alloys

作　　者：张兴孟 毛卫民[1] 朱文志[1] 

机构地区：[1]北京科技大学材料科学与工程学院

出　　处：《特种铸造及有色合金》2014年第12期1336-1339,共4页Special Casting & Nonferrous Alloys

基　　金：国家重点基础研究发展计划(973计划)资助项目(2011CB606302)

摘　　要：采用约束棒模具热裂评价法,研究了Zn、Mg、Cu对7075铝合金热裂性能和组织的影响。结果表明,单一调节Zn时,热裂倾向系数(HCS)先减小,然后增大,达到最大值后减小。Zn含量为5.44%时,HCS最小,为76.8,Zn含量为6.44%时,HCS最大,为141.6。单一调节Mg时,HCS随Mg含量的增加而逐渐减小,Mg含量为1.68%时,HCS为最大,107.2;Mg含量为3.68%时,HCS最小,为72。单一调节Cu时,HCS先增大然后减小,Cu含量为1.80%时,HCS最小,为72;Cu含量为1.50%时,HCS最大,为101。7075约束棒的断裂方式为沿晶断裂,合金中不含共晶组织时,抗热裂性好;共晶组织较多,但又不足以明显补缩时,抗热裂性最差;共晶组织沿晶界大量分布,有利于补缩,热裂倾向小。7075铝合金约束棒试样铸态组织主要由树枝状α-Al相和η-MgZn2相组成。Influences of Zn, Mg and Cu on hot cracking behavior and microstructure of 7075 aluminum alloys were investigated by constrained rod casting （CRC） mold. The results demonstrate that hot cracking sensitivity （Hcs） is firstly decreased,and then increased to reach the maximum value, and then decreased with increasing in the content of Zn. Hcsmin is 76.8 when the Zn content is 5.44% and Hcsmax reaches 141.6 when the Zn content is 6.44% . Hcs is decreased with Mg content increase, where ncsmin reaches 72 when the Mg content is 3.68% and Hcsmax is 107.2 with 1.68% Mg content. Hcs is firstly in- creased and then decreased with Cu content increase. Hcsmin is 72 when the Cu content is 1.80% and Hcsm is 101 when the Cu content is 1.50% . The fracture mode of 7075 aluminum alloys is character- ized by intergranular fracture. Cracks are propagated along the low melting eutectic microstructure at the grain boundaries. Hot cracking resistance is well with little eutectic microstructure, and hot cracking resistance is worse with a higher eutectic microstructures in condition of solidification shrinkage with poor feeding fed well. Hot cracking resistance is high with eutectic microstructures distributed along crain boundary to be beneficial for feeding. The as-cast microstructure of 7075 aluminum alloys mainly consist of a-A1 and r/-MgZn2.

关 键 词：7075铝合金 热裂倾向系数 共晶组织 

分 类 号：TG146.21[一般工业技术—材料科学与工程] TG245[金属学及工艺—金属材料]