The effect of cooling rate on thermophysical properties of magnesium alloys
- PDF / 258,206 Bytes
- 9 Pages / 584.957 x 782.986 pts Page_size
- 22 Downloads / 191 Views
M. Aljarrah and J.T. Wood Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON, Canada N6A 5B9
M. Medraja) Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, Canada, H3G 1M8 (Received 13 August 2010; accepted 13 January 2011)
Thermophysical properties such as phase-transformation temperatures and enthalpy of solidification depend on the composition and on the solidification conditions. To analyze the effects of the cooling rate on these properties, three commercial magnesium alloys (AZ91D, AM60B, and AE44) have been studied. Phase-transformation temperatures and enthalpy of solidification of these alloys have been measured using differential scanning calorimetry. Solidification curves have been obtained experimentally and compared with thermodynamic calculations. For all the studied alloys, it has been found that with increasing cooling rate, liquidus temperature increases slightly, whereas solidus temperature decreases. Enthalpy of solidification increases significantly with increasing cooling rate. Finally, relationships of phase-transformation temperature and enthalpy of solidification as a function of cooling rate have been established on the basis of the general power law. Using these relationships, the phase-transformation temperature and enthalpy of solidification have been predicted at high cooling rates and compared with experimental results.
I. INTRODUCTION
AZ91D, AM60B, and AE44 alloys have been in widespread use in the automotive industry processed mainly by casting. In designing cast automotive components, it is important to know how these alloys solidify at different cross sections of the casting resulting in precise structure and mechanical properties. Cooling rate is one of the many factors that affect the solidification behavior of castings, which influences the thermophysical properties and consequently the microstructure and mechanical properties. As a result, these castings are prone to the development of porosity and other microstructural defects that lead to local variation of mechanical properties. Therefore, the knowledge of the thermophysical properties during solidification enables the designer to ensure that the casting will achieve the desired properties for its considered application. Thermal analysis technique is a useful tool to obtain the value of phase-transformation temperature and heat of solidification of multicomponent alloys. Many researchers1–13 studied the solidification behavior of magnesium a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.24 974
J. Mater. Res., Vol. 26, No. 8, Apr 28, 2011
http://journals.cambridge.org
Downloaded: 19 Mar 2015
alloys, but the effect of cooling rate on phase-transformation temperatures and enthalpy of solidification has not been investigated extensively in the literature. Hence, this work has been initiated to investigate experimentally the effect of cooling rate on phase-transformation temperatures and heat of solidi
Data Loading...
