The correlation of microstructure features, dry sliding wear behavior, hardness and tensile properties of Al-2wt%Mg-Zn alloys

Dendritic Spacing/Columnar Grain Diameter of Al–2Mg–Zn Alloys Affecting Hardness, Tensile Properties, and Dry Sliding Wear in the As‐Cast/Heat‐Treated Conditions

“…As reported by Reis et al., results of scanning electron microscopy–energy‐dispersive X‐ray spectroscopy (SEM–EDS) analyses and X‐ray diffraction (XRD) confirmed that both alloys have microstructures consisting of the dendritic matrix of α‐Al with C14‐Laves MgZn 2 and τ ‐phase Al 2 Mg 3 Zn 3 precipitates in interdendritic spacings . Despite the phase equilibrium diagram of Figure a, which predicts only the presence of α‐Al and C14‐LAVES phases at low temperatures, the τ phase precipitates as a consequence of solidification occurs under nonequilibrium cooling conditions in the present experiments that restrict the diffusion of the alloying elements into the α‐Al matrix, which remained segregated in the liquid phase.…”

“…Alumina ceramic balls (10 mm diameter) were used as the counterface material due to their higher hardness (1500 HV) in comparison with those of the alloys, restricting surface damage of the pin. For all wear tests, identical parameters to those used in our previous work were adopted (14.7 N normal load, 1.8 m s −1 sliding speed, and 1000 m total sliding distance) for comparison purposes . The parameters were selected for inducing high stress (Hertzian contact pressure—750 MPa maximum—higher than the alloy yield strengths), severe wear damage in the disc, and high‐speed contacts for preventing excessive wear‐track heating; similar conditions to those found in structural components of automobile suspension parts.…”

“…Furthermore, the smaller grain size restricts the dislocation motion during plastic deformation. In the present investigation, specific equations for each alloy were required to express the trend of the HB and UTS experimental results, whereas in the work reported by Reis et al., a single equation represented the evolution of hardness and strength responses with λ 2 for the alloys in the as‐cast condition …”

“…Experimental Hall–Petch‐type expressions were obtained by a curve‐fitting technique (dashed lines); in the as‐cast condition, these properties are dependent on the inverse square root of λ 2 and CGD, whereas in the heat‐treated condition, this dependence is on the inverse square root of CGD. For comparison purposes, the experimental equations for HB and UTS obtained in the previous work reported by Reis et al., using the same alloys and similar experimental procedures for the as‐cast condition, are shown in Figure a,c (solid lines) …”

“…The alloys were melted at 720 °C ± 7 °C and solidified using a water flow of 4 L min −1 on the bottom of the mold, permitting tip growth rates during solidification ranging from 0.37 to 0.21 mm s −1 and liquid thermal gradients from 13 1 to 2 °C mm −1 for those positions from the bottom to the top of the ingots. The details of the casting assembly and procedures have been described in our previous work . However, in this investigation, the ingots were solidified under higher cooling rates due to a more efficient cooling system; consequently, the obtained microstructures were more refined than those previously observed.…”