淬火转移时间对AA357铝合金力学性能与微观组织的影响  

Influence of Quenching Transfer Time on the Mechanical Properties and Microstructure of A357 Aluminum Alloys

作　　者：樊振中[1] 郑卫东[1] 张显峰[1] 李红[2] 王少华[1] 

机构地区：[1]中国航空工业集团公司北京航空材料研究院,北京1000952 [2]北京理工大学材料学院,北京100081

出　　处：《科技导报》2014年第32期22-27,共6页Science & Technology Review

基　　金：中国航空工业第一集团公司航空科学基金项目(KZ36110221)

摘　　要：采用OM、DSC、SEM与TEM,结合力学性能测试研究淬火转移时间对A357铝合金力学性能与微观组织的影响。结果表明：随着淬火转移时间由3 s延长至49 s,A357铝合金经T6热处理后的抗拉强度、屈服强度与延伸率分别由351 MPa、275MPa与12.4%降低至320 MPa、254 MPa与6.5%,合金材料的抗拉强度连续下降,屈服强度变化较小,延伸率呈现出先上升后下降的变化趋势。初生与共晶Si相逐渐由细长的针状或片层状转变为椭圆球状或棒状,平均长度为10～25μm,平均宽度为5～10μm,当淬火转移时间超过35 s后,初生与共晶Si相则仍以细长的针状或片层状形貌为主。拉伸断口形貌以韧窝断裂为主,附带部分沿晶断裂,随着淬火转移时间的增加,断口表面韧窝数量随之减少,沿晶断裂裂纹数量不断增加;Mg与Si元素集中分布于晶粒边界处的二元与三元共晶组织中,Al元素广泛分布于晶粒内部及晶粒边界处;人工时效过程析出的Mg2Si强化相长度约为0.2～1μm,宽度为0.02～0.08μm,且随着淬火转移时间的延长,Mg2Si强化相的析出数大量减少,长径比不断下降,合金材料的强度与塑性随之降低。In the present work, the effects of quenching transfer time on the mechanical properties and microstructure of A357 aluminum alloys are investigated by using optical microscopy （OM）, scanning electron microscope （SEM）, differential scanning calorimetry （DSC）, transmission electron microscopy （TEM）, as well as tensile mechanical properties testing methods. The results show that with the increase of quenching transfer time from 3 s to 49 s, the tensile strength, yield strength and elongation of A357 aluminum alloys are reduced from 351 MPa, 275 MPg, and 12.4% to 320 MPa, 254 MPa, and 6.5% , respectively after T6 heat treatment, together with a continuous declining of tensile strength, tiny variation of yield strength and a continuous variation of elongation. The average length and width size of silicon particles are 10 - 25 μm and 5 - 10 μm, respectively, and the morphologies of neonatal and eutectic silicon particles evolve from needle and lamellar structures to spheroidal and rod structures after the T6 heat treatment process. Silicon particles are shown as needle and lamellar mostly when the quenching transfer time exceeds 35 s. The tensile fracture morphology is observed as dimple and intergranular fracture, and the intergranular fracture is increased with the prolonged quenching transfer time. Magnesium and silicon elements are distributed nearby the grain boundaries and the binary and ternary eutectic structures, whereas the aluminium elements are concentrated in the grain and grain boundaries. The length and width size of Mg2Si phase are 0.2 - 1 μm and 0.02 - 0.08 μm, respectively, the precipitation amount and size ratio of Mg2Si phase are declined, together with the decreases of strength and ductility of A357 aluminum alloy with the prolonged quenching transfer time.

关 键 词：A357铝合金 淬火转移时间 力学性能 微观组织 

分 类 号：TG156.3[金属学及工艺—热处理] TG146.21[金属学及工艺—金属学]