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Dieringa H.,Helmholtz Center Geesthacht | Zander D.,RWTH Aachen | Gibson M.A.,Co operative Research Center | Gibson M.A.,CSIRO
Materials Science Forum | Year: 2013

The development of creep resistant high pressure die casting (HPDC) alloys is one of the main focuses in magnesium research. Alloying elements like rare earths, calcium, strontium or scandium added to the necessary aluminium for die casting have already been introduced. Newly developed barium containing magnesium alloys with three levels of alloying additions were processed via HPDC and their compression creep response at 200 °C was evaluated. DieMag633 (Mg-6Al-3Ba-3Ca) displays the best creep resistance followed by DieMag422 (Mg-4Al-2Ba-2Ca) and then DieMag211 (Mg-2Al-1Ba-1Ca). Stress exponents from tests at different applied stresses were calculated. The creep tests were also accompanied by microstructural investigations and mechanical property evaluation. © (2013) Trans Tech Publications, Switzerland. Source


Clegg R.E.,Central Queensland University | Clegg R.E.,Co operative Research Center | Clegg R.E.,Bureau Veritas | McLeod A.J.,Central Queensland University | McLeod A.J.,Co operative Research Center
Annual Conference of the Australasian Corrosion Association 2013: Corrosion and Prevention 2013 | Year: 2013

High chromium white cast irons are a useful family of materials for wear resistant applications in high temperature Bayer liquor, as they combine high abrasion resistance with reasonable corrosion resistance. The performance of white irons in high temperature caustic solutions has been found to depend on alloy composition and heat treatment. In this paper, the corrosion behaviour of three grades of high chromium white cast iron was studied in pure caustic solutions at temperatures from 170C to 280°C, with an exposure time of 10 days. The oxide films formed under these conditions were characterised and corrosion penetration depths were estimated on the basis of oxide penetration. It was found that at lower temperature, the corrosion proceeded by a mechanism of degradation of the carbide-matrix interface with significant corrosion of the carbide component of the alloy. At higher temperatures, preferential corrosion of the matrix occurred exposing carbide particles to mechanical damage. This work will assist in our understanding of the mechanism of degradation of white irons in high temperature, high caustic environments. Copyright © 2013 by the Australasian Corrosion Association. Source


Easton M.,Co operative Research Center | Easton M.,Monash University | Sweet L.,Co operative Research Center | Sweet L.,Monash University | And 7 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2012

An investigation into the hot tear susceptibility of ternary Al-Si-Mg alloys has been made using direct crack observation, measurement of load response, and predictions made by a modified Rappaz-Drezet-Gremaud (RDG) hot tearing model. A peak in both the hot tear susceptibility and the load at solidus occurred at approximately 0.2Si and 0.15Mg, and then the hot tear susceptibility decreased as the total solute content increased. In general, a good correlation was found among the observation of cracks, the load at solidus, and the predictions of the RDG hot tearing model, although it was shown that correlation with the RDG model depended critically on the fraction solid at which solid coalescence was assumed to occur. A combination of these approaches indicated that when the total Si+Mg content and the Si:Mg ratio increased toward four, a decrease occurred in the hot tear susceptibility because of an increase in the amount of final eutectic formed. At the lowest Si:Mg ratio of 0.25, the RDG model also predicted a lower relative hot tear susceptibility than that measured by the load at solidus. In these alloys, the final stages of solidification are predicted to occur over a large temperature range, and hence, both the predictions of the RDG model and the measurement of the load were dependent on which fraction solid was chosen for grain coalescence. In the alloys studied in this article, the formation of small amounts of the ternary eutectic Al+Mg2Si+Si caused the highest hot tear susceptibility. © The Mineral, Metals & Materials Society and ASM International 2012. Source


Easton M.A.,Co operative Research Center | Easton M.A.,Monash University | Gibson M.A.,Co operative Research Center | Gibson M.A.,CSIRO | And 8 more authors.
Materials Science Forum | Year: 2011

This paper reports on the results of the castability of three MRI alloys (153A, 153M and 230D). MRI153A was found to cast best, with castings produced rated with a quality approaching AZ91. MRI230D produced the next best castings, whilst MRI153M showed the worst castability across a range of conditions. However, these alloys showed a tendency to build-up oxide in the melt transfer tube leading to melt transfer problems. This was particularly severe in MRI230D. © (2011) Trans Tech Publications. Source


Sivarupan T.,Co operative Research Center | Taylor J.A.,Co operative Research Center | Caceres C.H.,Co operative Research Center | Caceres C.H.,University of Queensland
TMS Annual Meeting | Year: 2014

Quasi-directionally solidified plates were sand cast using unmodified Al-xSi-yCu-0.1Mg-0.5Fe alloy with two Si (x = 4.5 or 9 mass%) and three Cu (y = 0, 1 or 4mass%) contents, and the size of the intermetallic phase particles ( β-Al5FeSi and Al2Cu) assessed at constant secondary dendrite arm spacing (SDAS) using optical microscopy and back scattered electron images. Increasing the concentration of Si alone or in combination with Cu refined the β-Al5FeSi platelets, whereas increasing Cu at constant Si shows an SDAS and Si level dependent effect. Source

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