scholarly journals Effect of N/C Ratio on Precipitation Behavior of (Cr,Fe)23C6 Carbide in Novel Cast Austenitic Heat-Resistant Steels during Directional Solidification

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 678 ◽  
Author(s):  
Yinhui Zhang ◽  
Jian Yang
Keyword(s):  
Directional Solidification ◽  
Room Temperature ◽  
Microstructural Characterization ◽  
Eutectoid Reaction ◽  
Precipitation Behavior ◽  
Gasoline Engines ◽  
Heat Resistant ◽  
Δ Ferrite ◽  
Liquid Metal Cooling ◽  
Heat Resistant Steels

The precipitation of (Cr,Fe)23C6 carbide could significantly degrade the mechanical properties of Nb-bearing cast austenitic heat-resistant steels, designed for exhaust components of automotive gasoline engines at 1000 °C. In the current research, the precipitation behavior of (Cr,Fe)23C6 carbide in these alloys, with great variations in N/C (Nitrogen/Carbon) ratio, was investigated through the liquid metal cooling directional solidification method, combined with thermodynamic calculations. Microstructural characterization suggested that the (Cr,Fe)23C6 carbide formed in the steady-state zone and the competitive zone, upon cooling to room temperature, after the solidification ended. It grew in the colony of the δ-ferrite, through the eutectoid reaction and showed different concentrations of C and Si from the δ-ferrite. Its precipitation temperature decreased significantly with increasing the N/C ratio, thereby retarding its precipitation. Therefore, the quantity of (Cr,Fe)23C6 carbide could be limited though increasing the N/C ratio of this type of alloys.

scholarly journals Dependence of Precipitation Behavior and Creep Strength on Cr Content in High Cr Ferritic Heat Resistant Steels

2009 ◽  
Vol 3 (3) ◽  
pp. 457-463 ◽  
Author(s):  
Yoshinori MURATA ◽  
Koji YAMASHITA ◽  
Masahiko MORINAGA ◽  
Toru HARA ◽  
Kazuhiro MIKI ◽  
...  
Keyword(s):  
Creep Strength ◽  
Precipitation Behavior ◽  
Cr Content ◽  
Heat Resistant ◽  
Heat Resistant Steels

Microstructure and microtexture of a Nb-16%Si (DS) Alloy

1995 ◽  
Vol 53 ◽  
pp. 122-123
Author(s):  
J. A. Sutliff ◽  
B. P. Bewlay
Keyword(s):  
High Temperature ◽  
Directional Solidification ◽  
Room Temperature ◽  
Microstructural Characterization ◽  
Crystallographic Analysis ◽  
Directionally Solidified ◽  
Heat Treated ◽  
Other Orientation

In-situ composite Nb-Si alloys have been studied by several investigators as potential high temperature structural materials. The two major processing routes used to fabricate these composites are directional solidification and extrusion of arc-cast solidified ingots. In both cases a stable microstructure of primary Nb dendrites in a eutectoid of Nb and Nb5Si3 phases is developed after heat treatment. The Nb5Si3 phase is stable at room temperature and forms as a decomposition product of the high temperature Nb3Si phase. The anisotropic microstructures developed by both directional solidification and extrusion require evaluation of the texture to fully interpret the fracture and other orientation dependent mechanical behavior of these composites.In this paper we report on the microstructural characterization of a directionally solidified (DS) and heat treated Nb-16 at.%Si alloy. The microtexture of each of the phases (Nb, Nb5Si3) was determined using the Electron BackScattering Pattern (EBSP) technique for electron diffraction in the scanning electron microscope. A system employing automatic diffraction pattern recognition, crystallographic analysis, and sample or beam scanning was used to acquire the microtexture data.

OS1302 Dependence of precipitation behavior and creep strength on Cr content in high Cr ferritic heat resistant Steels

2008 ◽  
Vol 2008 (0) ◽  
pp. _OS1302-1_-_OS1302-2_
Author(s):  
Yoshinori MURATA ◽  
Kohji YAMASHITA ◽  
Masahiko MORINAGA ◽  
Toru HARA ◽  
Kazuhiro MIKI ◽  
...  
Keyword(s):  
Creep Strength ◽  
Precipitation Behavior ◽  
Cr Content ◽  
Heat Resistant ◽  
Heat Resistant Steels

Effect of titanium on second phase precipitation behavior in 9–12Cr ferritic/martensitic heat resistant steels

Rare Metals ◽  
2011 ◽  
Vol 30 (S1) ◽  
pp. 497-500 ◽  
Author(s):  
Fengshi Yin ◽  
Liqian Tian ◽  
Bing Xue ◽  
Xuebo Jiang ◽  
Li Zhou
Keyword(s):  
Second Phase ◽  
Phase Precipitation ◽  
Precipitation Behavior ◽  
Heat Resistant ◽  
Heat Resistant Steels

scholarly journals Uneven Precipitation Behavior during the Solutionizing Course of Al-Cu-Mn Alloys and Their Contribution to High Temperature Strength

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Jinlong Chen ◽  
Hengcheng Liao ◽  
Heting Xu
Keyword(s):  
High Temperature ◽  
Tensile Testing ◽  
Room Temperature ◽  
Fine Particles ◽  
Microstructural Characterization ◽  
Tension Test ◽  
High Temperature Strength ◽  
Precipitation Behavior ◽  
Cu Content ◽  
The Core

The dispersoid precipitation behavior during the solutionizing and aging of Al-xwt.%Cu-1.0 wt.% Mn alloys (x = 2.0, 4.5, and 7.5) and contribution to mechanical properties were investigated using tensile testing and microstructural characterization. A shell-core structure of primary α-Al dendrites is found in Al-Cu-Mn alloys, in which the Cu content in the shell is higher than that in the core. The area of shell zone (Cu-rich) increases with an increase in Cu content in the alloy. Large amounts of fine dispersoid Al-Cu-Mn particles precipitate in solution. An alloy with low Cu content results in only the TMn (Al20Cu2Mn3) particles being precipitated. However, in an alloy with high Cu content, AlCu3Mn2 particles are first found to precipitate beside TMn. However, this precipitation behavior is uneven. The precipitation zones in the solution microstructure are consistent with the Cu-rich regions in the as-cast microstructure. A number of fine particles (dozens nanometer in size) are first found to precipitate on the rod-like TMn particles during the aging phase. The redissolution and granulation of the eutectic CuAl2 phase during the solutionizing process result in the formation of particle-free bands between the precipitation zones. The tension test at 300°C demonstrates that the increase in high temperature strength is due to the dispersoid precipitation during solutionizing, and the precipitation behavior in the aging phase has little or no effect, however, largely improves the tensile strength at room temperature. High temperature strength is significantly increased with an increase in Cu content, which correlates to an increase in number and decrease in size of TMn and AlCu3Mn2 particles.

Precipitation behavior of high-Nb containing modified HR3C heat-resistant steels during isothermal aging

2019 ◽  
Vol 35 (14) ◽  
pp. 1717-1726
Author(s):  
Jiaming Bai ◽  
Yong Yuan ◽  
Peng Zhang ◽  
Jingbo Yan ◽  
Caiyin You
Keyword(s):  
Isothermal Aging ◽  
Precipitation Behavior ◽  
Heat Resistant ◽  
Heat Resistant Steels

scholarly journals Formation of Nb(C,N) Carbonitride in Cast Austenitic Heat-Resistant Steel during Directional Solidification under Different Withdraw Rates

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2397 ◽  
Author(s):  
Yinhui Zhang ◽  
Jian Yang
Keyword(s):  
Directional Solidification ◽  
Solid Phase ◽  
Eutectic Reaction ◽  
Interdendritic Liquid ◽  
Interlamellar Spacing ◽  
Quantitative Relationship ◽  
Microstructural Characterization ◽  
Chinese Script ◽  
Resistant Steel ◽  
Heat Resistant

It is recognized recently that primary “Chinese-script” Nb(C,N) carbonitride is critical to the development of cast austenitic heat-resistant steels for ultra-high temperature applications. In this paper, the precipitation behavior of Nb(C,N) carbonitride in a novel creep and fatigue resistant steel was investigated by the use of the liquid metal cooling directional solidification (LMC-DS) method under different withdraw rates. Thermodynamic calculations were also performed to aid in the understanding of the solidification behavior. Microstructural characterization and thermodynamic calculation agreed that the alloy solidified in the path of primary austenite, eutectic Nb(C,N) carbonitride, and secondary ferrite, regardless of the withdraw rate. However, the primary and secondary dendrite arm spacing decreased significantly with an increase in the withdraw rate, and a quantitative relationship was established. Furthermore, the eutectic reaction range increased at a higher withdraw rate, due to the rapid increase of the solid phase fraction and the accumulation of solutes in the interdendritic liquid phase. This gave rise to a decline in the interlamellar spacing of primary Nb(C,N) carbonitride sheets and rods for the higher withdraw rate. Therefore, a fine “Chinese-script” Nb(C,N) carbonitride in this type of alloys can be achieved through increasing the withdraw rate or the cooling rate during casting.

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