The Effects Of Constrained Groove Pressing Plus Cold Rolling On The Microstructure And Mechanical Properties Of H65Brass

Constrained groove pressing as one of the severe plastic deformationmethod, has great potential in refining grains into ultrafine grains withoutchanging the cross-section. In this present study, H65brass was deformed byCGP firstly, and then by CGP/cross-CGP plus cold rolling. The effects of CGPand combined deformation on the microstructure and properties were studiedby the optical microscopy, scanning electron microscopy, transmissionelectron microscopy, micro-hardness test, tensile test and X-ray diffractionprofile analysis. Thermo-stability of the sample subjected to this combineddeformation technique was also studied.H65brass was subjected to CGP, and the results are as follows: the grainsof H65brass get refined after CGP, which are13.1μm and12.8μm respectivelyafter ten passes of CGP and cross-CGP. With the increasing of CGP passes, thegrains get refiner, and the number of deformation twins is greater, and themicrostructure is getting more homogeneous; the mechanical properties ofH65brass are greatly improved after both CGP and cross-CGP, yet cross-CGPcan lead to finer grains, better homogeneity and mechanical propertiescompared with CGP.The grains of H65brass are not further refined by subsequent cold rolling,but the number of deformation twins in the sample is higher and thehomogeneity of the sample is also improved with the increasing of the rollingreduction. After the deformation of CGP plus cold rolling, the hardness andstrength are further improved, and with the increasing of CGP passes and therolling reduction, the hardness and strength are higher, yet the elongation islower. The difference between CGP plus cold rolling and cross-CGP plus coldrolling is that the materials subjected to cross-CGP plus rolling get moredeformation twins, better homogeneity, higher hardness and strength ratherthan CGP plus rolling. After the deformation of H65brass by ten passes of CGP plus30%cold rolling, the hardness is improved by155%, and thesurrender strength by345%, and the tensile strength by72%.As for the thermo-stability of the sample subjected to ten passes of CGPand30%cold rolling, the microstructure and the mechanical strength remainstable under300℃; when above300℃, the grains begin to grow coarser andthe mechanical properties start to drop dramatically with the temperaturerising.