Abstract
An effort to obtain superior impact properties for Al-7Si-0.35 Mg alloy is presented,where modification with 0.02 wt％Sr and 0.1 wt％La as well as solution treatment was jointly employed.The samples were solution treated at 535 ℃ for 15 min to 12 h.The microstructure,fracture mecha-nism,and their correlation with the impact properties of the alloy were studied in detail mainly through optical micro-scopy(OM),scanning electron microscopy(SEM)and oscillography impact test.The results show that the addition of Sr and La refined the eutectic Si particles significantly from～2.05 pm(modified with Sr alone)to～0.75 pm in as-cast microstructure,leading to a very homogeneous dis-tribution of spheroidized Si particles in the alloy solution treated at 535 ℃ for 8 h.The alloy exhibits excellent impact toughness up to 75 J·cm-2,which is much higher than the maximum impact toughness of the alloys modified by Sr alone(～46 J·cm-2).The major reason for this remarkable increase in the impact property is the dramatic increase in crack initiation energy.The dispersoid-free zones(DFZs)near the eutectic regions mainly consist of the ductile Al-matrix,which exhibits excellent ductility.The ductile Al-matrix of the DFZs hinders the crack propagation,resulting in a significant increase in crack propagation energy.
基金项目
Beijing Natural Science Foundation(L223001)
NETL
NSTL
万方数据