The ultimate tensile strength of 250 MPa, 0.2% proof stress of 150 MPa, and fracture strain of 10% at the as-cast condition for Al-1.5Mn-X alloys, were objective in this development. As ternary elements, Ca, Mg, Ti and Zn were initially chosen and the values in ¦Mk of the s-orbital energy level in alloys were adjusted to be less than 0.017. Their proof stress and fracture strain increased and decreased as ¦Mk increased, respectively. The composition of promising alloy was decided to Al-1.5Mn-2.4Mg with ¦Mk of 0.029 on the basis of the relation between tensile properties and ¦Mk. This as-cast alloy showed the · uts · 0.2 and ¾ f of 270, 135 MPa and 18% showing excellent corrosion resistance in the NaCl solution, which resulted in the approximate satisfaction of the objective. The interaction between the proof stress and dislocation density or hindrance for dislocation migration at the constant strain could be explained by ¦Mk, which might lead to the indication of solid solution hardening level using this parameter for Al-1.5Mn-X ternary alloys.

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Three-dimensional local number, LN3D, and two-dimensional local number, LN2D, were defined as the number of gravity centers (GCs) of second phase particles in the measuring sphere and circle with specially determined radiuses, respectively, whose centers were put on GCs of noticed particles. LN3D and LN2D represent local number density including a noticed and its neighboring particles and each particle has a specific value. We suggested the quantitative method to evaluate the particle spatial distribution using the relative frequency distributions of LN3D and LN2D, and this method was examined by computer experiments using overlap permissive spheres. It was shown that randomness of second phase particles was correctly evaluated in 3-and 2-dimensions by this method, and the average and variance of LN3D and LN2D are proper descriptors to evaluate the spatial distribution randomness of second phase particles. It was also shown that spatial distribution randomness of 2-dimensional particles appeared on cut planes of 3-dimensional particles having uniform random arrangement can be evaluated by this method regardless of both the particle volume fraction and the particle size distribution.

The effect of particle clustering distribution on the damage accumulation and the deformation behavior is investigated in the particle reinforced metal-matrix composites. The clustering tendency of the Al-10 vol%SiC composite is evaluated by the normalized 2-dimensional local number density (LND2D) of the particle. It is found that the uniform material having a spatial distribution close to the random distribution has higher flow stress and larger elongation. The particle/matrix delamination is easy to occur preferentially at the particles of larger size in the more clustered regions in tensile deformation. Composites with lower clustering tendency have larger strain hardening capacity than those with more clustering one.