Residual stress induced mechanical property enhancement in steel encapsulated light metal matrix composites

Macro hybridized systems consisting of steel encapsulated metal matrix composites (MMCs) were produced with the goal of creating a low cost/light weight system with enhanced mechanical properties. The systems exhibit the high strength and modulus commonly expected from steels and high specific stiffness and low density observed in MMCs. The material combination also works to alleviate the high density of steels and the poor ductility of the MMCs. Furthermore, a coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized to improve the ductility of the MMCs. Systems consisting of an A36 or 304 stainless steel shell with an Al-SiC or Al-Al2O3 shell are evaluated via neutron diffraction to quantify bulk residual stresses. The analysis shows variation in the measured strain due to steel thickness, difference in CTE between materials, and position within the composite. Improvements in ductility and yield stress are a result of these strains.