机械切屑诱发的局部冷铁效应与富铁相选择性析出机理OA

Taking the Al-12Si-Fe alloy as the matrix and charging the cutting chips with different mass fractions(0-3%)to establish a coupled effect field of local chilling-heterogeneous nucleation,the influence of it on solidification microstructure and mechanical properties was systematically investigated.The results show that with insufficient chip feed(≤1.5%),only local chilling and solute segregation occur,leading to coarsening of eutectic/primary Si.With an appropriate amount(2.5%),oxide films and impurity clusters on the chip surfaces serve as potential nucleation substrates,significantly increasing nucleation density and promoting equiaxed grain formation,suppressing large-scale segregation of Fe-rich phases,thereby improving microstructural homogeneity and toughness.Whereas excessive charging chips(3.0%)act as crack initiation sites due to poor interfacial wetting and fusion.When the chip addition is 2.5%,the tensile strength of the alloy is increased from approximately 181 MPa to 213 MPa and the elongation is increased from approximately 4.5%to 6.4%.Furthermore,based on critical nucleation work,secondary dendrite arm spacing,and columnar-to-equiaxed transition(CET)conditions,a quantitative relationship between"chip addition-effective undercooling-equiaxed grain density"was established and an optimal process parameter window was proposed,providing a new approach for precise microstructure/property control and high-value utilization of recycled Al-Si-Fe alloys.