Formation Mechanism Of In-situ Iron-rich Nanoparticle In Copper Alloy

Formation mechanism of in-situ iron-rich nanoparticle in copper alloy melt has been studied in this paper. Solidification conditions, strength of convection, constituent of elements and adding alloying elements have a pronounced effect on morphology and microstructure of iron-rich nanoparticles. The finely dispersed iron-rich nanoparticles in the matrix can be obtained under the directional solidification condition, strengthening mechanisms of iron-rich nanoparticles for single crystal Cu-Fe alloy was described.Results show that, nanoparticles were indexed to be iron-rich phase both in Cu-Fe alloy and Cu-Fe-Co alloy, the matrix Cu and iron-rich nanoparticles form a completely coherent relation. Nanoparticles are divided into three types according to their shape:Type Ⅰ, nanoparticles are spherical, with their size is 2-50nm. Type Ⅱ, nanoparticles are near spherical, whereas the boundary of nanoparticles appear sunken, with their size is 50-100nm. Type Ⅲ, the shape of nanoparticles is petal-shaped, with the size is larger than 200nm. The microstructure of iron-rich nanoparticle changed by adding Co, twins appeared with nanoparticle size is about 20 nm. The results of DSC tests and designed water quenching experiments show that the iron-rich nanoparticles are directly formed in the Cu-Fe alloy melt instead of precipitating from α-Cu. Mechanism that how iron-rich nanoparticles are uniformly embedded in the matrix was described.A single crystal Cu-Fe alloy with finely dispersed precipitate iron-rich nanoparticles was fabricated under directional solidification condition. The tensile strength and the elongation of the Cu-Fe alloy observed by measurement have increased simultaneously. Nanoparticles which have coherent interface with matrix can improve the distribution of dislocations in the matrix. Some dislocations can slip through the nanoparticle along the coherent interface and some dislocations can enter into the nanoparticles. The distribution of dislocations in the matrix has been improved. Thus to improve the tensile strength of single crystal Cu-Fe alloy without sacrifice the ductility simultaneously.