Research on high strength and creep behavior of in-situ (Al2O3+ZrB2)/7055 Al nanocomposites

In this study, to achieve high strength, high ductility and good creep resistance, in-situ Al2O3 and ZrB2 nano -particles were introduced into 7055 aluminum alloy subjected to the deformation of hot rolling. The interface between nanoparticles and Al matrix displayed tightly-bonded and there were orientation relationships (ORs) between them: [124]Al2O3//[211]Al,(021)Al2O3//(111)Al, [020]ZrB2//[022]Al. The precipitates were easy to nucleate at the interface than in the matrix due to the low energy barrier to overcome. Precipitates like eta and Al2Cu had the ORs with the matrix: [1123]eta//[110]Al, [111]Al2Cu//[110]Al. The nanoparticles along with the precipitates had the effect of both promotion and inhibition to the recrystallization process. The particle-induced improvement for the strength was due to the excellent work-hardening ability. Moreover, mechanical performance of the (Al2O3 + ZrB2)/7055 Al nanocomposites exhibited the tensile strength of 749 MPa and the elongation of 21.81%, which indicated 14.3% and 11.8% higher than the matrix. The plastic zone and dislocation punched zone of the nanoparticles had been calculated during the crack process. The Al2O3 and ZrB2 nanoparticles indicated the high -temperature creep resistance ability with the steady creep rate of the (Al2O3 + ZrB2)/7055 Al composites 6- 17 times higher than the matrix, in which the values of apparent stress exponent (n), apparent activation energy (Q) and threshold stress were 9.48, 374.13 kJ/mol and 50.13 MPa, respectively. The stress exponent of 5 suggested that the dislocation climb was dominative in creep process. In addition, the strengthening contributions, toughness mechanism and creep behavior were discussed.

Automated summary

In this study, in-situ Al2O3 and ZrB2 nanoparticles were introduced into 7055 aluminum alloy to achieve high strength, high ductility, and good creep resistance. The nanoparticles were tightly bonded with the aluminum matrix and had orientation relationships with it. The nanoparticles and precipitates showed both promotion and inhibition effects on the recrystallization process. The (Al2O3 + ZrB2)/7055 Al nanocomposites exhibited improved mechanical performance and high-temperature creep resistance compared to the matrix.