Microstructure evolution and mechanical properties of in-situ ZrB2/Al7085 nanocomposites during hot rolling deformation

Abstract

In this study, ZrB2/Al7085 nanocomposites were fabricated by in-situ reaction with KBF4 and K2ZrF6 fluoride powders during casting, then hot deformation and heat treatment were applied to the sheet product. The deformation by hot rolling was employed to change the distribution of second phases and ZrB2 nanoparticles and significantly improve the microstructure of the matrix. TEM results indicate the semi-coherent relationship between ZrB2 particle and α-Al on the interface without intermediate products. The contributions of ZrB2 particles on composite are described by refining Al7085 grain size to 47% as heterogeneous nuclei during solidification and accelerating to decrease the residual stress and reduce anisotropy during heat treatment. Meanwhile, Al3Zr precipitate in composites is refined to half size in Al 7085. Compared to the Al7085, mechanical property on composite is enhanced when the ZrB2 volume fraction achieves 1% after quenching with 465 ℃−10 min and artificial aging of 120 ℃−5 h/160–10 h. The strengthening mechanisms are grain refinement, coefficient of thermal expansion, Orowan strengthening, and load transfer effect and corresponding strengthening contributions are 3.6 MPa,7.7 MPa,20 MPa, and 2.7 MPa. Our study shows the roles of ZrB2 particles act on composite in different processing statuses and provides the basic strengthening way caused by ZrB2 nanoparticles. Our study shows the roles of ZrB2 particles act on composite in different processing statuses and provides the basic strengthening way caused by ZrB2 nanoparticles.