Compressive creep behavior of hot-pressed Si3N4 ceramics using alumina and a rare earth solid solution as additives

a−SiAlON (a’) is a solid solution of a−Si3N4, where Si and N are substituted by Al and O, respectively. The principal stabilizers of the a’-phase are Mg, Ca, Y and rare earth cations. In this way, the possible use of the yttrium-rare earth oxide mixture, CRE2O3, produced at FAENQUIL, in obtaining these SiAlONs was investigated. Samples were sintered by hotpressing at 17500C, for 30 minutes, using a sintering pressure of 20 MPa. Creep behavior of the hot-pressed CRE-a-SiAlON/b-Si3N4 ceramic was investigated, using compressive creep tests, in air, at 1280 to 1340 0C, under stresses of 200 to 350 MPa, for 70 hours. This type of ceramic exhibited high creep and oxidation resistance. Its improved high-temperature properties are mainly due to the absence or reduced amount of intergranular phases, because of the incorporation of the metallic cations from the liquid phase formed during sintering into the Si3N4 structure, forming a a’/b composite.

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Effect of Ca and Rare Earths on Compressive Creep Behavior of Mg-4Al Alloy

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.190-191.457 ◽

2012 ◽

Vol 190-191 ◽

pp. 457-461

Author(s):

Chun Ping Du ◽

Dao Fen Xu ◽

Bin Wu Wang

Keyword(s):

Rare Earth ◽

Creep Behavior ◽

Rare Earths ◽

Creep Resistance ◽

Compressive Creep ◽

Ca Addition ◽

Special Apparatus ◽

Before And After ◽

Poor Creep Resistance ◽

Better Than

The effect of Ca and rare earths on compressive creep behavior of Mg-4Al alloy was investigated with a special apparatus. The microstructures were analyzed by OM, XRD, SEM and EDS before and after compressive creep test. The results reveal that a small amount of Ca was added into AE41 alloy in order to refine the crystalline structure and improve the creep resistance. Comparing with NdPr rare earths alloy, the creep resistance of LPC rare earths alloy decreases, but is still better than AE41 alloy. The as-cast microstructure of AE41 alloy is mainly composed of α-Mg matrix and Al11Nd3 phase. The acicular Al11Nd3 phase is prone to decompose at high temperature, which leads to the poor creep resistance of AE41 alloy. The acicular Al11RE3 phase is gradually replaced by Al2Ca and Al2RE with Ca addition into AE41. LPC rare-earth mixture is in cluster at grain boundaries so that the creep resistance is worse than that of alloy containing NdPr rare-earth mixture.

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COMPRESSIVE CREEP BEHAVIOR OF REACTORCONTROL ROD MATERIAL Ag-In-Cd ALLOY

ACTA METALLURGICA SINICA ◽

10.3724/sp.j.1037.2013.00247 ◽

2013 ◽

Vol 49 (8) ◽

pp. 1012 ◽

Cited By ~ 2

Author(s):

Hongxing XIAO ◽

Chongsheng LONG ◽

Le CHEN ◽

Bo LIANG

Keyword(s):

Creep Behavior ◽

Compressive Creep

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Effect of Rare Earth Ce on Deep Stamping Properties of High-Strength Interstitial-Free Steel Containing Phosphorus

Materials ◽

10.3390/ma13061473 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1473

Author(s):

Hao Wang ◽

Yanping Bao ◽

Chengyi Duan ◽

Lu Lu ◽

Yan Liu ◽

...

Keyword(s):

Solid Solution ◽

Grain Size ◽

Rare Earth ◽

High Strength ◽

Rolling Process ◽

P Element ◽

Second Phase ◽

Strengthening Effect ◽

Interstitial Free ◽

If Steel

The influence of rare earth Ce on the deep stamping property of high-strength interstitial-free (IF) steel containing phosphorus was analyzed. After adding 120 kg ferrocerium alloy (Ce content is 10%) in the steel, the inclusion statistics and the two-dimensional morphology of the samples in the direction of 1/4 thickness of slab and each rolling process were observed and compared by scanning electron microscope (SEM). After the samples in each rolling process were treated by acid leaching, the three-dimensional morphology and components of the second phase precipitates were observed by SEM and energy dispersive spectrometer (EDS). The microstructure of the sample was observed by optical microscope, and the grain size was compared. Meanwhile, the content and strength of the favorable texture were analyzed by X-ray diffraction (XRD). Finally, the mechanical properties of the product were analyzed. The results showed that: (1) The combination of rare earth Ce with activity O and S in steel had lower Gibbs free energy, and it was easy to generate CeAlO3, Ce2O2S, and Ce2O3. The inclusions size was obviously reduced, but the number of inclusions was increased after adding rare earth. The morphology of inclusions changed from chain and strip to spherical. The size of rare earth inclusions was mostly about 2–5 μm, distributed and dispersed, and their elastic modulus was close to that of steel matrix, which was conducive to improving the structure continuity of steel. (2) The rare earth compound had a high melting point. As a heterogeneous nucleation point, the nucleation rate was increased and the solidification structure was refined. The grade of grain size of products was increased by 1.5 grades, which is helpful to improve the strength and plasticity of metal. (3) Rare earth Ce can inhibit the segregation of P element at the grain boundary and the precipitation of Fe(Nb+Ti)P phase. It can effectively increase the solid solution amount of P element in steel, improve the solid solution strengthening effect of P element in high-strength IF steel, and obtain a large proportion of {111} favorable texture, which is conducive to improving the stamping formability index r90 value.

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