The enhanced microhardness in a rapidly solidified Al alloy

The objective of the present study is to explore the feasibility of producing 7075 Al alloy ribbons with the increased microhardness via rapid solidification processing, namely melt spinning. Our results show that the melt spun+aged 7075 Al alloy ribbons exhibit approximately 17% (307 MPa) higher microhardness than that of the coarse-grained (CG) counterpart solid-solution treated+aged under the same conditions. The higher microhardness of the melt spun+aged 7075 Al alloy stems from its microstructural features, including (i) sub-micrometric/micrometric sized grains, (ii) intragranular subgrains, and (iii) nanoscale precipitates with inter-precipitate distance slightly smaller than that in the CG counterpart. In an effort to understand the microstructure in melt spun+aged 7075 Al alloy, the microstructural evolution during aging of the as-melt spun 7075 Al alloy was analyzed and discussed. By quantifying the contributions of precipitation, grain boundary, dislocation, solid solution and subgrain boundary strengthening to the yield strength based on the microstructural analysis, the higher microhardness of the melt spun+aged 7075 Al alloy ribbons was rationalized.