Study of the Effect of Solidification Structures on the Strength of Metals

摘要

Ingots of the A13Ni-A1 eutectic were unidirectionally solidified, hydrostatically extruded by amounts up to 60%, and tensile properties evaluated. Tensile strengths up to 36,700 psi with 2.25% elongation at maximum load (total elongation over 3.0%) were obtained on specimens with an initial colony microstructure. Analysis of the data, while still incomplete, indicates that one or more extrusion variables can have effects of the same order of magnitude as the microstructural variables of the material being studied. In the other phase of the research on light-metal alloys (i.e. Mg base eutectics) tensile data was obtained on unidirectionally solidified specimens of all alloys under investigation. Compression tests were run to obtain a more reasonable evaluation of the intrinsic strength of these alloys, all of which are rather brittle. Further evidence that the alloys are behaving as reinforced composites is given by the fact that the tensile stress-strain curves usually have the shape expected from anisotropic two phase composites. It should be noted that the tensile strengths observed are as high as any cast magnesium base alloy known to the authors and that the compressive strengths, on a strength to density ratio, range up to 975,000 in. This latter property may be attractive in certain ballistic applications. (Author)