scholarly journals Effects of Holmium Additions on Microstructure and Properties of A356 Aluminum Alloys

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 849 ◽  
Author(s):  
Qiang Wang ◽  
Zhiming Shi ◽  
Hong Li ◽  
Yaming Lin ◽  
Ningyu Li ◽  
...  
Keyword(s):  
Complete Loss ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Element ◽  
Microstructure And Properties ◽  
Abnormal Growth ◽  
Sr Modification ◽  
Comprehensive Properties ◽  
Eutectic Si ◽  
A356 Aluminum ◽  
Intrinsic Orientation

Sr-modification of A356 alloys has distinct shortages due to the volatilization and oxidation during remelting and pouring, which often reduce the modification efficiency and mechanical properties of the alloys. To avoid the adverse effects and enhance the comprehensive properties, the effects of heavy rare earth element holmium (Ho) modification on the microstructure and properties of the alloy were investigated. Ho addition inhibited the intrinsic orientation growth of (111)Al planes and stimulated the growth of the (200)Al planes for α-Al crystals. The addition of 0.2 wt.% Ho produced the best refinement effect for α-Al grains; 0.3 wt.% of Ho addition yielded the most distinct modification effect for eutectic Si phases, which was further improved by a T6 treatment. The extra addition of 0.4 wt.% Ho resulted in the complete loss of the refinement and modification effects and in the abnormal growth of the α-Al crystals. Ho additions produced Al3Ho phases containing Fe elements, which were distributed on the boundaries of the α-Al dendrites. The corrosion-proof performance was enhanced by Ho addition and the T6 treatment; the tensile strength and elongation achieved the highest value upon 0.2 wt.% of Ho addition and the T6 treatment. Moreover, the hardness was also enhanced by Ho additions in both states.

Rare-earth crystal chemistry of thalénite-(Y) from different environments

2018 ◽  
Vol 82 (2) ◽  
pp. 313-327
Author(s):  
Markus B. Raschke ◽  
Evan J. D. Anderson ◽  
Jason Van Fosson ◽  
Julien M. Allaz ◽  
Joseph R. Smyth ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Spatial Scales ◽  
Structure Refinement ◽  
X Ray Diffraction ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Element ◽  
X Ray ◽  
Golden Horn

ABSTRACTThalénite-(Y), ideally Y3Si3O10F, is a heavy-rare-earth-rich silicate phase occurring in granite pegmatites that may help to illustrate rare-earth element (REE) chemistry and behaviour in natural systems. The crystal structure and mineral chemistry of thalénite-(Y) were analysed by electron microprobe analysis, X-ray diffraction and micro-Raman spectroscopy from a new locality in the peralkaline granite of the Golden Horn batholith, Okanogan County, Washington State, USA, in comparison with new analyses from the White Cloud pegmatite in the Pikes Peak batholith, Colorado, USA. The Golden Horn thalénite-(Y) occurs as late-stage sub-millimetre euhedral bladed transparent crystals in small miarolitic cavities in an arfvedsonite-bearing biotite granite. It exhibits growth zoning with distinct heavy-rare-earth element (HREE) vs. light-rare-earth element (LREE) enriched zones. The White Cloud thalénite-(Y) occurs in two distinct anhedral and botryoidal crystal habits of mostly homogenous composition. In addition, minor secondary thalénite-(Y) is recognized by its distinct Yb-rich composition (up to 0.8 atoms per formula unit (apfu) Yb). Single-crystal X-ray diffraction analysis and structure refinement reveals Y-site ordering with preferential HREE occupation of Y2 vs. Y1 and Y3 REE sites. Chondrite normalization shows continuous enrichment of HREE in White Cloud thalénite-(Y), in contrast to Golden Horn thalénite-(Y) with a slight depletion of the heaviest REE (Tm, Yb and Lu). The results suggest a hydrothermal origin of the Golden Horn miarolitic thalénite-(Y), compared to a combination of both primary magmatic followed by hydrothermal processes responsible for the multiple generations over a range of spatial scales in White Cloud thalénite-(Y).

scholarly journals Petrogenesis of Heavy Rare Earth Element Enriched Rhyolite: Source and Magmatic Evolution of the Round Top Laccolith, Trans-Pecos, Texas

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 423 ◽  
Author(s):  
Brent Elliott
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Geochemical Evolution ◽  
Magmatic Differentiation ◽  
Magmatic System ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Element ◽  
Element Concentrations ◽  
Stage Crystallization

The Round Top rhyolite located in Trans-Pecos Texas is enriched in Be, F, Li, Nb, Rb, Sn, Th, U, Y, Zr, and rare earth elements (REEs). REE-bearing minerals are mainly ubiquitous nano-scale accessory phases throughout the groundmass, incorporated in synchysite-group minerals, xenotime-(Y), Y- and Ce-rich fluorite, and zircon. The rhyolite is peraluminous, high-silica, alkaline (not peralkaline), with elevated heavy rare earth element concentrations and anonymously negative Eu values. Pervasive spongy groundmass and recrystallization textures are consistent with the elevated and remobilized Zr, Th, and Y + HREE (heavy rare earth element) concentrations and a high field strength element (HFSE) soluble, sub-alkalic, F-rich, magmatic system. REE-bearing minerals are present as late-magmatic, interstitial phases and attributed with closed-system, post-magmatic, hydrothermal alteration. Petrogenetic modeling provides scenarios that explain the geochemical evolution and REE complexing behavior in evolved rhyolite magmas, and determines possible source compositions and evolution. Trace element models suggest a system typical of having extensive magmatic differentiation. The resulting rhyolite magma is indicative of a silica-rich magmatic system enriched in H2O, Li, and/or F that could be considered transitional between pure silicate melt and hydrothermal fluid, where fluorine-ligand complexing was prevalent through late magmatic cooling and crystallization processes. Thorough differentiation and high fluorine activity contributed to the late stage crystallization of REE-bearing minerals in the Round Top rhyolite.

Microstructure and Properties of Al-Cu-Mn Alloy with Y, Zr and (Y+Zr)

2017 ◽  
Vol 898 ◽  
pp. 334-344
Author(s):  
Ting Biao Guo ◽  
Feng Zhang ◽  
Qi Li ◽  
Chen Wang ◽  
Wan Wu Ding
Keyword(s):  
Tensile Strength ◽  
Performance Improvement ◽  
Great Influence ◽  
The Other ◽  
Refined Grains ◽  
Microstructure And Properties ◽  
Comprehensive Properties ◽  
Important Significance ◽  
Better Than ◽  
Strengthening Method

As an important strengthening method, micro alloying has been widely used to improve the comprehensive properties of aluminum alloy. The research on microstructures and properties of Al-Cu-Mn alloy with Y, Zr and (Y, Zr) was conducted through OM, SEM and EDS methods. Three addition methods were comprehensively compared and the important significance of elements and relevant precipitates distribution to performance improvement was explored. The results show that adding different contents of Y, Zr and (Y, Zr) has great influence on microstructure and properties of Al-Cu-Mn alloy. Fluidity of the (Y+Zr)-containing alloy was significantly higher than that of the Zr or Y-containing one. The hardness and elongation of the Zr-containing alloy were also better than the other two groups, while with the increase of addition amounts from 0 to 0.2 %, it showed a decreasing trend. When the content was 0.3%, the grains of the Y and (Y+Zr)-containing alloys were well refined and the tensile strength and hardness increased as well, and Y-containing alloy presented the best tensile strength. After T6 heat treatment, the mechanical properties of the Y and (Zr+Y)-containing alloys were enhanced due to the dispersed θ phase and completely refined grains. And both ductile fracture ratios increased. When the content was more than 0.3%, the reticular θ phase formed that was extremely unfavorable to properties of the studied alloy. It appears that the addition of Y and Zr has an important influence on improving the properties of the Al-Cu-Mn alloy. And Y, Zr and (Y+Zr) dosages should be adjusted reasonably in the range of 0.1-0.3% to optimize and improve the alloy performance.

scholarly journals The Relationship between Residual Amount of Sr and Morphology of Eutectic Si Phase in A356 Alloy

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3222 ◽  
Author(s):  
Wenda Zhang ◽  
Shixuan Ma ◽  
Zhenhua Wei ◽  
Peikang Bai
Keyword(s):  
A356 Alloy ◽  
Sand Mold ◽  
Sr Modification ◽  
Treatment Processes ◽  
Modification Effect ◽  
Residual Amount ◽  
Eutectic Si ◽  
The Relationship ◽  
Modification Treatment ◽  
Alloy Cast

This paper studied the relationship between the residual amount of Sr and the morphology of the eutectic Si phase in A356 obtained through different modification treatment processes; additionally, the cooling rates of molds were studied. The eutectic Si phase revealed a satisfactory modification effect at residual Sr amounts above 0.01 wt % in A356 alloys cast using an iron mould. Complete modification of the eutectic Si phase could be achieved at a Sr additive amount 0.03 wt % in an A356 melt. The addition of higher amounts of Sr (~0.04–0.06 wt %) did not improve the modification effect. With the addition of 0.06 wt % Sr into A356 alloy melt and holding at 750 °C, the anti-fading capacity of Sr modification effect could be sustained for 120 minutes. More Sr is needed to obtain a good modification of eutectic Si for an A356 alloy cast using a sand mold.

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