科研之友
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摘要
This study was aimed at identifying underlying strengthening mechanisms and predicting the yield strength of as-extruded Mg-Zn-Y alloys with varying amounts of yttrium(Y) element. The addition of Y resulted in the formation of ternary I(Mg3 YZn6), W(Mg3 Y2 Zn3) and LPSO(Mg12 YZn) phases which subsequently reinforced alloys ZM31 + 0.3 Y, ZM31 + 3.2 Y and ZM31 + 6 Y, where the value denoted the amount of Y element(in wt%). Yield strength of the alloys was determined via uniaxial compression testing, and grain size and second-phase particles were characterized using OM and SEM. In-situ high-temperature XRD was performed to determine the coefficient of thermal expansion(CTE), which was derived to be 1.38 × 10(-5 K-1 and 2.35 × 10-5 K-1 for W and LPSO phases, respectively. The individual strengthening effects in each material were quantified for the first time, including grain refinement, Orowan looping, thermal mismatch, dislocation density, load-bearing, and particle shearing contributions. Grain refinement was one of the major strengthening mechanisms and it was present in all the alloys studied,irrespective of the second-phase particles. Orowan looping and CTE mismatch were the predominant strengthening mechanisms in the ZM31 + 0.3 Y and ZM31 + 3.2 Y alloys containing I and W phases, respectively, while load-bearing and second-phase shearing were the salient mechanisms contributing largely to the superior yield strength of the LPSO-reinforced ZM31 + 6 Y alloy.
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