ISSN:
1662-9779
Quelle:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Thema:
Physik
Notizen:
The process of thixoforming incorporates a series of forming processes in the semi-solidstate, which can be categorized between the conventional processes of forging and casting andcombines the advantages of these processes. Thixoforming of steels in the semi-solid state, requiresround, solid particles (globulites) in a liquid matrix which is deformed with low forming forces. Inorder to achieve laminar material flow and to produce segregation-free components, the materialmust fulfil diverse criteria. First, the melting interval should be as large as possible for an easytemperature regulation. Next, low solidus and liquidus temperatures are advantageous regardingtool loading. Additionally, thixoformable steels should show a melting behaviour that is finegrainedand globular. Furthermore, these steels should possess low contents of intraglobular liquidphase fractions.This paper gives a survey of the current state of steel Thixoforming and deals with the developmentof adaptive heat treatment strategies. Regarding the structure formation and the development ofsuitable heat treatment strategies, the once semi-solid state yields new structures that can be appliedin ways not previously possible with conventional hardening processes. New microstructures andup to date unknown better mechanical properties can be adjusted with an optimised heat treatmentstrategy. By this, new fields of application for thixo-materials can be entered and also advancedprocedures for special applications can be established. For example the steel X210CrW12 leads to avery hard material with high wear-resistance, which can be used at higher temperatures than theconventional hardened material. In general, new generic microstructures after thixoforming resultsin unexpected favourable mechanical properties. Problems arise with respect to segregation andpores which resulting in inhomogeneous property distributions
Materialart:
Digitale Medien
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.141-143.695.pdf
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