High-Temperature Mechanical Properties of Aluminum Alloy Matrix Composites Reinforced with Zr and Ni Trialumnides Synthe
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INTRODUCTION
THE high-temperature mechanical properties of conventional aluminum alloys are unable to meet the requirements of mechanical properties of new automotive engines that work at temperatures above 300 C.[1] At such high temperatures, coarsening or dissolution of the strengthening phases at elevated temperature results in loss of mechanical properties of the alloy and make
LIWEN PAN and ZHILIU HU are with the Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, School of Resources, Environment and Materials, Guangxi University, Nanning 530004, P.R. China and also with the Center Ecological Collaborative Innovation for Aluminum Industry in Guangxi, Nanning 530004, P.R. China. SAINAN ZHANG, CHAO YANG, and YANJUN ZHAO are with the Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, School of Resources, Environment and Materials, Guangxi University. YI YANG and NIKHIL GUPTA are with the Composite Materials and Mechanics Laboratory, Department of Mechanical and Aerospace Engineering, Tandon School of Engineering, New York University, Brooklyn, NY 11201. Contact e-mail: [email protected] Manuscript submitted July 28, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
them unsuitable for engine applications.[1] Aluminum matrix composites have been studied as promising materials for such applications.[2,3] In-situ aluminum matrix composites have been investigated and have shown promising tensile and wear properties for such applications[4] but their high-temperature properties are not determined. The a-Al matrix of these alloys is mainly strengthened by eutectic mixture and intermetallic phases such as Al2Cu and Mg2Si, depending on the alloy composition. However, spheroidization of Si particles may reduce the high-temperature strength of Al-Si alloys.[5] The Al2Cu and Mg2Si intermetallic phases are effective in improving strength and creep resistance of the alloys at elevated temperatures but only below 200 C.[6,7] Many cast Al-Si alloys have hypereutectic composition and contain coarse, angular primary silicon phase, resulting in low strength and ductility of the alloys.[8] Casting defects such as porosity and inclusions are observed in cast Al-Si alloys due to a broad ‘‘mushy zone’’. These defects considerably degrade the mechanical properties and service life of the alloys.[8] Therefore, it is desired to develop new high-temperature alloys as substitutes to the conventional Al-Si alloys.
Studies have attempted to introduce thermally stable trialuminides by microalloying of transition metals (TM) to improve elevated-temperature mechanical properties of aluminum alloys.[1,9–11] Precipitation strengthening was provided by Al3Zr and Al3Ni by adding Zr and Ni, respectively, in aluminum alloys is found to be promising in this regard. Al3Zr serves as a high-temperature strengthening phase due to its high melting point (1580 C), high modulus of elasticity (205 GPa), high thermal stability (425 C),[12] slow diffusivity in Al-matrix (at 400 C, DZr = 1.2 9
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