高Si多组元铝镁焊料冲击韧性损失研究  

Impact Toughness Loss of High Silicon Multi-Contents Al-Mg Welding Materials

作　　者：路全彬[1] 龙伟民[1] 董显[1] 沈元勋[1] 张宏超[1] 

机构地区：[1]郑州机械研究所新型钎焊材料与技术国家重点实验室,河南郑州450001

出　　处：《稀有金属》2017年第11期1237-1242,共6页Chinese Journal of Rare Metals

基　　金：国家国际科技合作计划项目(2015DFA50470);河南省基础与前沿技术研究项目(162300410215)资助

摘　　要：解理断裂通常发生在体心立方金属和密排六方金属,面心立方的铝合金极少发现解理断裂。通过金相显微镜(OM)、扫描电镜(SEM)和能谱分析(EDS)等分析方法和冲击试验研究了Si对铸态多组元Al-5Mg-Mn-Cr-Ti焊料断裂韧性损失,着重研究了Si致焊料解理断裂机制。研究发现,当Si含量大于0.5%时面心立方的铝镁焊料中有解理断裂。随焊料中Si含量的增加,Mg2Si金属间化合物相增加,Mg2Si在晶界析出。Mg2Si相室温延展率几乎为零,硬度达HV 450,存在严重的室温脆性。焊料晶粒边界存在的Mg2Si相在应力作用下开裂形成初生裂纹,初生裂纹形成后扩展到相邻α-Al晶粒,α-Al发生断裂,该断裂属于裂纹形核控制断裂。同时Si聚积在α-Al密排面(111)面上,弱化密排面原子结合力,断裂沿α-Al密排面扩展。Si含量从0.15%增加到0.8%时焊料的冲击韧性急剧劣化,冲击功从35 J下降到14 J。断裂特征由延性断裂转变为脆性解理断裂为主的混合型断裂。Si增加,焊料断裂韧性损失严重,Si等于0.5%为焊料韧脆转变的临界点。Cleavage fracture usually occurred in the body-centered cubic metal and hexagonal close-packed metal, but rarely occurred in the face-centered cubic aluminum alloy. The influence of Si contents on impact toughness loss of the casting AL-SMg-Mn-Cr-Ti alloys was investigated with optical microscopy （OM）, scanning electron microscope （SEM）, energy dispersed spectrum （EDS） and Charpy pendulum impact tests. The influence of Si element on mechanism of cleavage fracture was investigated. Cleavage fracture occurred when Si content was more than 0.5% of AL-Mg welding materials. With the Si content increasing, MgESi phases increased. Mg2Si was a severely brittle phase at room temperature for its almost zero percentage elongation and the microhardness was HV 450. Mg2Si phases on grain boundary of alloys were cracking and primary cracks formed. The α-Algrain fractured after the primary cracks extended to the adjacent α-Al grain. This fracture was controlled by cracks nucleation mechanism. The interatomic bonding force of close-packed plane was weaker for Si atoms accumulating on close-packed plane. The cracks propagated along the α-Al close-packed plane. With the Si content increasing from 0.15% to 0.8% , the Charpy energy reduced from 35 to 14 J, and the impact toughness changed from plasticity fracture to brittle fracture. So, with Si content increasing, the impact toughness lost seriously. Impact fracture transition from the ductile fracture to the brittle cleavage fracture occurred when the Si content was 0.5%.

关 键 词：铝镁焊料 硅焊料 冲击韧性 解理断裂 

分 类 号：TG422[金属学及工艺—焊接]