| The surface roughening and its evolution during plane-strain tension deformation were extensively investigated for 6022-T4 Al sheets. Three different scales of observation windows, microscopic, intermediate, and macroscopic windows, were used to systematically examine surface roughening phenomena in different scales. Analytical tools based on roughness metrology were introduced in order to quantify characteristics of surface roughening from different observation windows. Efforts were made to correlate surface roughening directly with the textural variations. Various plasticity parameters were employed to investigate plastic behavior of grains both on the surface and through the thickness.; 6022-T4 Al sheets exhibited anisotropy in the development of roughening patterns during plane-strain tension deformation. 1-D lineal roughening patterns were predominantly developed along the RD when the sample is pulled in the TD (T-sample). In particular, the lineal macroscopic roughening in T-samples showed the ribbing behavior evolving from the intermediate strain. However, 2-D diamonding or diagonal patterns were dominant when the sample is pulled in the RD (L-sample). Both types of roughening patterns gradually evolved from the microscopic scale to the macroscopic scale and from the early stage of straining to the final necking. Quantitative analysis of surface roughening supported that both amplitudes and major wavelengths gradually increase with strain. Two new roughness parameters, Rmh and Rpv, introduced in the present work successfully provided quantitative measures for the characterization of morphological features of the deformed and undeformed surfaces.; Experimental observations suggested that slip-banded and non slip-banded surface grains tend to form valleys and hills, respectively, wherever these two types of grains are adjacent to each other. In particular, slip bands tend to be produced in grains either with very few (1∼2) slip systems of high Schmid factors or with low Taylor factors. However, plastic interactions among the adjacent grains play a key role in determining the plastic responses of surface grains. It is reasonable to attribute the formation of macroscopic roughening to the combined effects of textural variations in the surface, subsurface and through the thickness, rather than emphasizing a single source. Experimental observations also suggested that all these factors contribute to the macroscopic roughening. |
