Abstract Scope |
The effect of transition metals, e.g. Ti, Zr, V, Nb, Cr, Ag, Mo, Hf, Sc, Ge, In, Ga Ti, Zr, V and Nb, on the microstructure and mechanical properties of Al-Si-Mg alloy has been studied. The application of a single micro-addition (up to 0.25%wt.) does not have a noticeable effect on the alloy microstructure, while a simultaneous combination of 4 micro-elements in the volume of up to 0.8%wt. leads to significant refining of grains and a modification of the eutectic. To improve mechanical properties, the T6 heat treatment has been developed. It consisted of solutioning at 520˚C for 4h and next ageing at 160˚C, 180˚C i 200˚C for 0.15 - 550h. The dependence hardness as a function of the aging time shows that the presence of transition elements in an Al-Si-Mg system leads to prolonged hardness while keeping the alloys at 180˚C. The tensile strength of the alloys containing Ti, Zr, Nb, V micro-additions after the optimal T6 (520˚C/4h and 180˚C/17.5h) has the following properties: R0.2 ≈ 240 MPa and Rm ≈ 380 MPa, at plasticity of 4.5 %. The TEM studies allow to identify the nano-precipitations responsible for the strengthening of alloys.
Acknowledgements
The research was supported by Polish science financial resources The National Centre for Research and Development, in frame of “Szybka Sciezka” program, project No POIR.01.01.01-00-0890/17. |