EFFECT OF COOLING RATE ON THE FORMATION OF 14H–LPSO STRUCTURE IN GWZ1032K ALLOY
ZHANG Song1,2, YUAN Guangyin1,2, LU Chen1,2, DING Wenjiang1,2
1. Light Alloy Net Forming National Engineering Research Center, School of Materials Science and Engineering, Shanghai
Jiao Tong University, Shanghai 200240
2, The State Key Laboratory of Metal Matrix Composite, School of Materials Science and Engineering, Shanghai
Jiao Tong University, Shanghai 200240
Cite this article:
ZHANG Song YUAN Guangyin LU Chen DING Wenjiang. EFFECT OF COOLING RATE ON THE FORMATION OF 14H–LPSO STRUCTURE IN GWZ1032K ALLOY. Acta Metall Sin, 2010, 46(10): 1192-1199.
Abstract Mg–10Gd–3Y–1.8Zn–0.5Zr (mass fraction, %) (GWZ1032K) alloys were fabricated by permanent mold casting and slow solidification with different cooling rates. The microstructures of the GWZ1032K alloys with different cooling rates were investigated by SEM, TEM and XRD. Two kinds of LPSO structure were observed, include lamellar 14H–LPSO structure in the grain interior and χ phase at the grain boundaries. Lamellar 14H–LPSO structure in α–Mg matrix propagated in the matrix with the decease of solidification rate, and filled the whole grain in the alloy solidified at 0.005 ℃/s. The second phase in the alloys also changed with deceasing the solidification rates, there are (Mg, Zn)3RE compounds only when solidification rate is 5 ℃/s, (Mg, Zn)3RE compounds and 14H–LPSO structured phase when solidification rates are 0.5 and 0.1 ℃/s, and 14H–LPSO structured χ phase only when solidification rates are 0.01 and 0.005 ℃/s. It was detected that (Mg, Zn)3RE compounds and χ phase existed simultaneously at the grain boundaries in the alloys at solidification rates of 0.5 ℃/s and 0.1℃/s, and the orientation relationship between them was determined to be [110] χphase//[223](Mg,Zn)3RE and ∠g(001)χ phase g(110) (Mg, Zn)3RE=8.4°.
Supported by Science and Technology Commission of Shanghai Municipality (No.08JC141412200), Program for New Century Excellent Talents in University (No.NCET–07–0554), and Open Research Fund Program by Jiangsu Key Laboratory of Advanced Metallic Materials (No.AMM200903)
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