High as-cast strength die-cast AlSi9Cu2Mg alloy prepared by nanoparticle strengthening with industrially acceptable ductility

摘要

High as-cast strength die-cast AlSi9Cu2Mg alloy was achieved with industrially acceptable ductility, via the addition of titanium diboride nanoparticles. The main intermetallic compounds in the die-cast AlSi9Cu2Mg alloy were identified as theta-Al2Cu and Q-Al5Cu2Mg8Si6 phases. The Fe-rich compound formed in the present die-cast alloy with a high Mn/Fe ratio of 3:1 was determined as the BCC structured alpha-Al-15(Fe,Mn)(3)Si-2 phase with a lattice parameter of a = 1.2702 nm, and the Fe-rich compound had highly faceted morphology with {110} surface termination. The Al matrix phase in the die-cast AlSi9Cu2Mg alloy was refined by similar to 65% from 18.1 mu m to 6.4 mu m, after adding 3.0 wt% titanium diboride nanoparticles. The titanium diboride nanoparticles in the alloy showed coherent interface with the Al matrix, with the (11-1) lattice face of Al parallel to the (0001) lattice face of titanium diboride. The as-cast AlSi9Cu2Mg alloy containing 3.0 wt% titanium diboride nanoparticles exhibited the high yield strength of 233 +/- 3 MPa and the tensile strength of 398 +/- 7 MPa, as well as the industrially acceptable elongation of 4.8 +/- 0.7%, and it showed at least 23% improvement in the as-cast yield strength over the existing diecast Al alloys. The strengthening by nanoparticle and coherent interface (similar to 32 MPa) was higher than that by the refining of Al matrix (similar to 10 MPa). The addition of titanium diboride nanoparticles also affected the fracture of the die-cast AlSi9Cu2Mg alloy, and cracks were prone to form in the Q and Fe-rich compounds, after the addition of titanium diboride nanoparticles. (C) 2020 Elsevier B.V. All rights reserved.