Borivoj Šuštaršič (Author), Jože Medved (Author), Srečko Glodež (Author), Marko Šori (Author), Albert Korošec (Author)

Abstract

Al-based alloyed powders, appropriate for the sintering procedure (powder metallurgy, P/M) contain the alloying elements with a high solid solubility in Al, enabling reaction and liquid-phase sintering. They are surface oxidised because of a high affinity of Al to oxygen. Besides, this type of powders contains a polymeric lubricant (wax), which reduces the friction on die walls during automatic die compaction into the final compact shape of a product. This lubricant has to be removed slowly during the first stage of sintering in order to prevent deformations and cracking of the product. Consequently, its sintering is very complex. Generally, these powders are sintered in pure nitrogen with a low dew point. The optimum sintering conditions are generally determined on the basis of light and scanning electron microscopy. The investigation can also be completed very successively with differential scanning calorimetry and thermo gravimetry. The first one allows an insight into the endo- and exothermic reactions, taking place during the heating and cooling of a compacted metal powder, and the second one allows an insight into the processes, connected with the mass loss (a reduction, a lubricant removal, etc.) or mass increase (an oxidation). The DSC/TG of three commercial Al-based alloyed powders was performed in the frame of our investigations. The results were compared with the theoretical thermodynamic-based calculations and the optimum sintering conditions were proposed.

Keywords

aluminijevi prahovi;sintranje;diferencialna vrstična kalorimetrija s termogravimetrijo;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UM FS - Faculty of Mechanical Engineering
Publisher: Inštitut za kovinske materiale in tehnologije Ljubljana
UDC: 621.762.5:669.71
COBISS: 18068246 Link will open in a new window
ISSN: 1580-2949
Parent publication: Materiali in tehnologije
Views: 837
Downloads: 92
Average score: 0 (0 votes)
Metadata: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Other data

Secondary language: Slovenian
Secondary title: DSC/TG prahov na osnovi Al primernih za P/M uporabo
Secondary abstract: Legirani prahovi na osnovi Al, primerni za sinter postopek (P/M, metalurgija prahov), vsebujejo zlitinske elemente z veliko topnostjo v trdnem Al, kar omogoča reakcijsko sintranje v prisotnosti tekoče faze. Zaradi velike afinitete aluminija do kisika so na površini oksidirani. Poleg tega vsebujejo ti prahovi polimerno mazivo, ki zmanjšuje trenje na stenah orodja med avtomatskim stiskanjem prahu v končno oblikovan izdelek. To mazivo moramo v prvi fazi procesa sintranja počasi odstraniti, sicer bi lahko prišlo do nepopravljive deformacije ali celo pokanja izdelka. Zato je njihovo sintranje zelo zahtevno. Navadno se sintrajo v čisti dušikovi atmosferi z nizko temperaturo rosišča. Poleg fizikalno-kemijske karakterizacije sintranih izdelkov s svetlobno in elektronsko mikroskopijo je za določitev optimalnih pogojev sintranja zelo uporabna diferencialna vrstična kalorimetrija, kombinirana s termogravimetrijo (DSC/TG). Prva omogoča vpogled v endo- in eksotermne reakcije, ki potekajo med segrevanjem in ohlajanjem kompaktiranega kovinskega prahu, druga pa s temi procesi povezano izgubo (redukcija, odstranitev maziva itd.) ali prirastek (oksidacija) mase. V okviru naših raziskav smo izvedli DSC/TG treh komercialno dosegljivih prahov na osnovi Al, ugotovljene reakcije smo primerjali z napovedmi teoretične termodinamike in predlagali optimalne pogoje sintranja teh prahov.
Secondary keywords: aluminium powders;sintering;differential scanning calorimetry and thermo gravimetry;
URN: URN:NBN:SI
Type (COBISS): Scientific work
Pages: str. 531-536
Volume: ǂLetn. ǂ48
Issue: ǂšt. ǂ4
Chronology: jul.-avg. 2014
ID: 9591238