Papers by Keyword: Solidification Mode

Abstract: Hot ductility in slab shell of two types of low Ni austenitic stainless steels was investigated via tensile test. Results showed that, reduction of area (RA) in Cr17Mn6Ni4Cu2N decreased gradually from surface to inside. However, RA in Cr15Mn9Cu2NiN shell surface was low, and increased from surface to inside. Analysis suggested that, the difference of RA between the two steels due to the different solidification process. In the shell of former steel, δ ferrite solidifies as the primary phase, then transforms into austenite. The space between primary arms increases from surface to inside, leading to the decrease of hot ductility. In the latter steel, δ ferrite does not solidify entirely as the primary phase because of the high cooling rate, but austenite solidifies directly from the retained liquid between δ ferrite dendrites. The change of solidification mode is most obviously in slab surface, which decreases its hot ductility.

Abstract: This paper describes the cast structure study of A357 aluminum alloy stress frame casting under consecutive solidification and simultaneous solidification by test and numerical simulation methods, with the conclusions of tensile tests by using of SEM and EDS analysis, the mechanical properties and fracture morphology were observed both under the cast and T6 heat-treatment state. Intergranular fracture cracks were observed to be the main failure mode in the casting state condition, cracks originated from the tissue defects and continued to proliferate until the tensile specimens were ruptured. Simultaneous solidification can decrease the casting shrinkage and micro-cavity and improve the mechanical properties of the castings. Dimple fracture was the dominated failure mode after T6 heat treatment state, the distribution of some intergranular cracks staggered with dimple fracture can surveyed under the fractography analysis. The superiority of simultaneous solidification was demonstrated by the numerical simulation of China casting CAE.