Effect of pass reduction on microstructure, mechanical properties and texture of hot-rolled 7075 alloy

Abstract

Mechanical properties, microstructure morphology and texture evolution of the hot rolled 7075 alloy with 11% and 16% pass reductions were analyzed via tensile test, optical microscope (OM), electron scanning microscope (SEM) and electron backscattered diffusion (EBSD). The results showed that the ultimate tensile strength (UTS) and yield strength (YS) of the hot rolled 7075 alloy with 11% pass reduction increases firstly, then decreases and eventually increases with increasing total rolling reduction. However, UTS and YS of the hot rolled 7075 alloy with 16% pass reduction increases obviously with increasing total rolling reduction. The maximum UTS value of 376 MPa and YS of 332 MPa were obtained in the hot rolled 7075 alloy with 11% pass reduction. The maximum elongation value of 20% is obtained at the 61% total rolling reduction. The microstructure of the hot rolled 7075 alloy consists of elongated grains and equiaxed grains. Work hardening, fine-grain strengthening and texture influence the mechanical properties of the hot rolled 7075 alloy together. Misorientation angle and high-angle grain boundary of the hot rolled 7075 alloy with 11% pass reduction decreases with increasing rolling pass, but low-angle grain boundary exhibited an obvious increase. Misorientation angle and high-angle grain boundary of the hot rolled 7075 alloy with 16% pass reduction underwent an obvious increase and then a slight change with an increase of rolling pass, but low-angle grain boundary showed an adverse changing trend. The texture intensity of the hot rolled with 11% pass reduction in the (100) crystal face is larger than those in the (110) crystal face and (111) crystal face. Texture created by hot rolling process with 11% pass reduction mainly distributed in the rolling and transverse directions. Texture intensity firstly decreased and then increased with an increase of rolling pass from 9 to 15. Higher texture intensity of the hot rolled 7075 alloy with 16% pass reduction occurred in (100) crystal face as compared to (110) and (111) crystal faces. Mechanical properties of the hot-rolled 7075 plates were improved via T6 heat treatment. It was attributed to recrystallization and precipitated second phase. The high mechanical such as YS of 446 MPa, UTS of 539 MPa and elongation of 11.6% were obtained in the hot-rolled 7075 plate with 16% pass reduction after T6 heat treatment. The texture intensity was reduced and distribution of texture was more random after T6 heat treatment.