Microstructure evolution and mechanical properties of the Sip/Zn-Al composite joints by ultrasonic-assisted soldering in air

Hypereutectic Al-27 Si alloys were joined without flux by ultrasonic-assisted soldering at 420 ℃ in air using Zn-5 Al the filler alloys,and Si particulate-reinforced Zn-Al based composites filler joints were obtained. The ultrasonic vibration introduced into soldering could influence the migration of Si particles and the microstructure of solidified Zn-Al based alloys. Both the distribution of Si particles and microstructure of the solidified Zn-Al based alloys affected the shear strength of joints. The shear strength increased with the ultrasonic vibration time. The highest average shear strength of joints reached to ～ 68. 5 MPa. Transcrystalline rupture mode was observed on the fracture surface.     

GCr15钢在平衡球上的失效分析

采用低倍酸洗、光谱分析和金相分析等手段对GCr15平衡球淬火后开裂原因进行了分析。分析结果表明,GCr15平衡球锻造后没有球化退火,且存在零件表面应力集中,在大的热应力和组织应力作用下,在盐水介质中淬火引起开裂。