ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
Thixoforming or Semi-Solid Metal Forming offers many advantages in comparison withcasting and conventional forging. The purpose of the present study is to provide the basicmicrostructure and deformation data for austenitic and ferritic stainless steel under mushy state. Aswell known, the stainless steels solidify in different modes according to the different chemicalcompositions. In this paper, microstructural evolution of austenitic stainless steel type 304 whichsolidifies in FA mode ( L → L +δ → L +δ +γ →δ +γ →γ ),austenitic stainless steel type 310Swhich solidifies in A mode ( L → L +γ →γ ), and ferritic stainless steel type 430 which solidifies inF mode ( L → L +δ →δ )[removed info]are investigated during partial remelting by way of SIMA (Strain InducedMelted Activation). The results show that A and F mode of stainless steels melt directly at the grainboundary without phase transformation during reheating. A banded structure, originating from theprimary dendritic segregation of the original ingots, is observed in type 310S steel during furtherheating. On the other hand, a perfect globular and insegregative two-phase semi-solid structure L +δcan be obtained while heated beyond the banded three-phase L +δ +γ semi-solid state in FA modeaustenitic stainless steel type 304. This spheroidization can be attributed to the peritectic reactionoccurred in the L +δ +γ semi-solid state. In addition, simple compression tests of these alloys insemi-solid state for varied combination of deformation rate and deformation temperature areconducted to examine the deformation behavior of stainless steel. Flow stress curves exhibit abruptchange in various alloys, even though in the same alloy such as type 304, various flow stresses areobserved according to the difference in inner microstructure or morphology. Stress of type 310S steelshows the most reduction as the deformation temperature increasing at the same strain rate condition.The Liquid is centralized to periphery by the compression force in all deformed test pieces. Fracture,observed in all alloys except type 304 steel in globular L +δ semi-solid state, should be resultedfrom the lack of liquid in L +δ +γ state of type 304 steel and solidification crack in type 310S andtype 430 steel. Deformation of solid particles occurs only in L +δ +γ state of type 304 steel. Last inthis paper, various deformation mechanisms are proposed for various microstructures
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/22/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.116-117.681.pdf
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