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Coarsening of the basketweave α + β microstructure in Ti-6Al-4V is a common phenomenon that occurs during thermal cycling in both additive manufacturing and cyclic heat treatment. Such a coarsening process is driven by multiple dissolution and precipitation transformations rather than by conventional Ostwald ripening. It is clear that during the first cycle, the complete dissolution of the thinnest α plates at the heating stage provides large spaces for surviving plates to regrow at the cooling stage, which results in coarsening after the first cycle. However, it is still unclear how the α plates continue to vanish and the remaining α plates sustainably coarsen in the repeated thermal cycles. In this study, cyclic heat-treatment experiments and phase-field simulations were conducted to illustrate the mechanism of sustained coarsening during thermal cycling. It was found that in addition to the complete dissolution of the thinnest α plates in the first thermal cycle, α-plate vanishing continued during repeated thermal cycling in two ways, which has not been reported before. The origin of such sustained vanishing of α plates is related to the Gibbs–Thomson effect. Moreover, the influences of cycling frequency and total duration on the transformation coarsening are detected. Both the experimental and simulation results indicate that long cycling duration results in severe coarsening, while for a given duration time, the final coarsening of the α plates is almost independent of the cycling frequency. [Display omitted] • During the repeated thermal cycling,α–plates vanishing can continue in three ways. • The origin of sustained vanishing of α plates is related to Gibbs–Thomson effect. • The transformation coarsening is more sensitive to cycling time than frequency. [ABSTRACT FROM AUTHOR]

• The Cr phase can be uniformly dispersed by addition of Y in the as-cast Cu-0.9Cr and Cu-1.45Cr alloys. • The effects of CRA and SSA processes on the properties of the Cu-0.9Cr-Y and Cu-1.45Cr-Y alloys were studied. • Y-containing Cu-Cr alloys posses better over-aging resistance because the coarsening of Cr is suppressed during CRA. • The difference of softening temperature between the Cu-Cr and Cu-Cr-Y alloys is investigated. The effects of Y content on the microstructure and properties of Cu-0.9Cr and Cu-1.45Cr alloys were investigated systematically in present manuscript. Cu-Cr-(Y) alloys were prepared by vacuum melting and casting, solid solution treatment at 960 °C, (90% cold rolling) and aging treatment at 460 °C. The results indicate that the addition of 0.1 wt% Y refines the eutectic structure of as-cast Cu-0.9Cr and Cu-1.45Cr alloys. Besides, the hardness of Cu-Cr-(Y) alloys after solid solution treatment increases with the increase of the Y content. CRA (cold-rolling and aging) process can enhance the hardness of peak-aged alloys compared with SSA (solid solution and aging), the peak-aged hardness and corresponding conductivity of cold-rolled alloys slightly increase by addition of Y. Especially, when CRA for 300 min, the ultimate tensile strength, hardness of Cu-0.95Cr-0.1Y alloy (433 MPa, 146.8 HV) are superior to those of Cu-0.9Cr alloy (333 MPa, 102 HV), indicating that addition of Y significantly inhibits the over-aging during CRA. The TEM results reveal that Cr precipitates of FCC and BCC structures exist in the Cu-Cr-Y alloy aged for 300 min, and Y element suppresses the coarsening of Cr precipitates and the reduction of dislocation density. Moreover, the softening temperature of peak-aged Cu-Cr-Y alloys is ~70 °C higher than that of Cu-Cr alloys since the addition of Y inhibits the coarsening of Cr precipitates. [ABSTRACT FROM AUTHOR]