Microstructure of Heavily Deformed Magnesium-Lithium Composites Containing Steel Fibers

Abstract

The microstructure of deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers was characterized to correlate the fiber size to the deformation strain and mechanical properties of the composite material. Micrographs taken using scanning and transmission electron microscopy techniques revealed fiber sizes larger than predicted from the deformation applied to the bulk composite. Deformation strain in the fibers, therefore, was less than in the bulk material. Measurements from SEM and TEM micrographs were used to calculate the actual deformation strain present in the fibers. This strain was then used to adjust rule-of-mixture (ROM) predictions of the strength of the composite material. However, the experimental strengths of these materials were still less than the adjusted ROM values, potentially due to the presence of fibers considerably larger than the average size measured stereologically. Of the many models used to describe the strengthening observed in DMMC materials, the Hall-Petch relationship best describes the experimental data. Details of the strengthening models are discussed in relation to these composite materials. Keywords Ames Laboratory Disciplines Metallurgy CommentsThis article is from Journal of Materials Engineering and Performance 7 (1998): 375-384, doi: 10.1361/ 105994998770347828. Posted with permission. RightsCopyright 1998 ASM International. This paper was published in Journal of Materials Engineering and Performance, Vol. 7, Issue 3, pp. 375-384 and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited. The microstructure of deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers was characterized to correlate the fiber size to the deformation strain and mechanical properties of the composite material. Micrographs taken using scanning and transmission electron microscopy techniques revealed fiber sizes larger than predicted from the deformation applied to the bulk composite. Deformation strain in the fibers, therefore, was less than in the bulk material. Measurements from SEM and TEM micrographs were used to calculate the actual deformation strain present in the fibers. This strain was then used to adjust rule-of-mixture (ROM) predictions of the strength of the composite material. However, the experimental strengths of these materials were still less than the adjusted ROM values, potentially due to the presence of fibers considerably larger than the average size measured stereologically. Of the many models used to describe the strengthening observed in DMMC materials, the Hall-Petch relationship best describes the experimental data. Details of the strength...

Recent progress in magnesium–lithium alloys

“…Strengths are also lower than predicted from ROM calculations because of the presence of fibres considerably larger than the average size measured stereologically. 92 The bcc/bcc material shows the potential for producing highly formable composite sheet materials by combining a ductile bcc matrix with a bcc reinforcing fibre. Figure 26 shows the different formability of Mg-4Li/27 vol.-%steel and Mg-12Li-2Nd/21vol.-%steel.…”