Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 25    No. 3    March 2015

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Effects of Cr content on microstructure and mechanical properties of single crystal superalloy
Zhen-xue SHI, Shi-zhong LIU, Xiao-guang WANG, Jia-rong LI

Science and Technology on Advanced High Temperature Structural Materials Laboratory,
Beijing Institute of Aeronautical Materials, Beijing 100095, China

Abstract:Two experimental single crystal superalloys with 2% Cr and 4% Cr (mass fraction) were cast in a directionally solidified furnace, while other alloying element contents were kept unchanged. The effects of Cr content on the microstructure, phase stability, tensile properties at 1100 °C and stress rupture properties at 1070 °C and 160 MPa of the single crystal superalloy were investigated. The results show that the size of γ′ phase particles become small and uniform, and the cubic shape turns a little regular with the increase of Cr content. The γ′ directional coarsening and rafting were observed in the 2% Cr and 4% Cr alloys after long term aging (LTA) at 1100 °C. The rafting rate of γ′ phase increased with increasing Cr content. Needle-shaped topologically close packed (TCP) phases precipitated and grew along fixed direction in both alloys. The precipitating rate and volume fraction of TCP phases significantly increased with the increase of Cr content. The tensile property of the alloy increased and the stress rupture properties of the alloy decreased with the increase of Cr content at high temperature. The increase of Cr content increased the partition ratio of TCP forming elements, Re, W, and Mo, and the saturation degrees of these elements in γ phases increased. Therefore, the high temperature phase stability of the alloy decreased with the increase of Cr content.

 

Key words: single crystal superalloy; Cr content; microstructure; phase stability; mechanical properties

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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