grain refinement
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2022 ◽  
Vol 211 ◽  
pp. 114510
Author(s):  
Yonghao Yu ◽  
Hongchao Kou ◽  
Mengyu Jia ◽  
Yichao Wang ◽  
Yarong Wang ◽  
...  
Keyword(s):  

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 600
Author(s):  
Lili Zhang ◽  
Yan Song ◽  
Linjie Yang ◽  
Jiuzhou Zhao ◽  
Jie He ◽  
...  

Synergistic effect of TiB2 (in form of Al-5Ti-1B) and La on grain refining results in Al-2Cu alloy was investigated. α-Al grains are significantly refined by Al-5Ti-1B. When trace La is added to the melt, further refinement is exhibited. Average grain size and nucleation undercooling of α-Al reduce first and then almost remain unchanged with La addition. Satisfactory grain refining result achieves when La addition level reaches 600 ppm. When more than 600 ppm La is added to the melt, La-rich particles form and the effect of solute La left in matrix on the microstructure almost no longer changes. Theoretical calculation results demonstrate that solute La segregates to Al melt/TiB2 particles interface along with Ti and Cu prior to α-Al nucleation and the synergistic effect of La and TiB2 particles on grain refinement mainly attributes to the enhancement in the potency of TiB2 particles to heterogeneously nucleate α-Al by trace La addition.


2022 ◽  
Vol 327 ◽  
pp. 45-53
Author(s):  
Jiehua Li ◽  
Maria Pammer ◽  
Ernst Neunteufl ◽  
Peter Schumacher

AZ80 alloy has been widely used to produce high performance Mg casting and wrought parts for high-end applications due to its high mechanical properties and deformation ability. However, at least two important issues still need to be solved in order to further improve its mechanical properties and deformation ability. Firstly, the grain size of α-Mg in AZ80 alloy is relatively large (more than 1000 µm) due to a lack of efficient grain refinement methodologies. Secondly, the size of the eutectic Mg17Al12 phase is also large and the distribution of the eutectic Mg17Al12 phase is continuous, which is very harmful for the mechanical properties, in particular to elongation. In this paper, these two important issues are investigated by adding Mg3N2 sub-micron particle into AZ80 alloy and thereby refining the α-Mg and the eutectic Mg17Al12 phase. Firstly, the Mg3N2 sub-micron particle was directly added into AZ80 alloy by using mechanically stirring in the semi-solid state, subsequently the melting temperature was increased above the liquidous temperature, and finally the melting was casted in the liquid state. It was found that the grain size of α-Mg can be refined from 883.8 µm to 169.9 µm. More importantly, the eutectic Mg17Al12 phase was also refined and the distribution became discontinuous. It should be noted that directly adding the Mg3N2 sub-micron particle into AZ80 alloy leads to a great loss of the Mg3N2 sub-micron particle due to the weak wetting behavior between the Mg3N2 sub-micron particle and Mg melt. The second methodology through mixing Mg3N2 sub-micron particles with AZ91 chips using a twin extruder was also used to prepare AZ91 master alloy with 3wt.% Mg3N2 sub-micron particle, which was subsequently added into AZ80 alloy in the liquid state. In this way, a significant grain refinement of α-Mg and a simultaneous refinement of the eutectic Mg17Al12 phase in AZ80 alloy was also achieved. The grain size of α-Mg can be refined from 883.8 µm to 325.9 µm. However, no significant grain refinement by using UST was observed. Instead, the grain size increases from 325.9 µm to 448.6 µm, indicating that the Mg3N2 sub-micron particle may lose its grain refinement potency due to possible aggregation and clustering. This paper provides an efficient and simple methodology for the grain refinement of α-Mg and the simultaneous refinement of the eutectic Mg17Al12 phase in AZ80 alloy.


2022 ◽  
Vol 327 ◽  
pp. 54-64
Author(s):  
Ivo Spacil ◽  
David Holec ◽  
Peter Schumacher ◽  
Jiehua Li

Different Ta concentrations together with stochiometric grain refiner (Al-2.2Ti-1B) in Al-Si-Mg based alloys were investigated with the aim to elucidate grain refinement mechanisms. Post-solidification microstructure was characterised using optical microscopy and scanning electron microscopy (SEM), with a special focus on the Ta-rich layer (more likely to be Al3Ta) on the basal planes (0001) of TiB2. A significant grain refinement was observed by using the solute Ta together with stochiometric grain refiner (Al-2.2Ti-1B). In order to further elucidate the formation of Ta-rich layer on the basal planes (0001) of TiB2, the Density Functional Theory (DFT) calculation were also performed to determine the interface energies of different interfaces and sandwich configurations, including Al (111), Al3Ti (112) and Al3Ta (112) at the interface of TiB2 basal plane (0001). It was found that the interface energy for Ti-terminated TiB2 at the interface throughout all configurations involved in this paper is lower than that for B-terminated TiB2, indicating that Ti-terminated TiB2 is more favourable. It was also found that the Al3Ta configuration yields the same interface energies as the Al3Ti configuration. Furthermore, the interface energy of the sandwich configuration also shows nearly identical values along the TiB2 // Al3Ti and TiB2 // Al3Ta interface energy, strongly indicating that the solute Ti can be fully replaced by the solute Ta.


Author(s):  
Jiawei Yang ◽  
Yijiang Xu ◽  
Sarina Bao ◽  
Shahid Akhtar ◽  
Ulf Tundal ◽  
...  

AbstractIt is well known that the filtration efficiency of ceramic foam filters (CFF) on aluminum melt can be significantly reduced by the addition of grain refiner particles under a high inclusion load. Also, it is usually considered that the filtration process has little impact on grain refinement efficiency. In this work, the influence of inclusions and filtration on the grain refinement effect of AA 6060 alloy has been studied. This was done through TP-1 type solidification experiments where the aluminum melt prior to and after the filter during a pilot-scale filtration test was investigated. In the experiments, 80 PPi CFFs were used to filtrate aluminum melt with an ultra-high inclusion load and two addition levels of Al–3Ti–1B master alloys. It is found that both inclusions and filtration significantly reduce the grain refinement efficiency of the grain refiner master alloys. A detailed characterization of the used filters shows that the reduction of grain refinement efficiency is due to the strong adherence of TiB2 particles to the oxide films, which are blocked by the CFF during filtration. A grain size prediction model based on deterministic nucleation mechanisms and dendritic growth kinetics has been applied to calculate the solidification grain size and estimate the loss of effective grain refiner particles during filtration. It is shown that due to the strong adherence between TiB2 particles and oxide films in the melt, the high addition level of aluminum chips also has an influence on reducing the grain refinement efficiency of aluminum melt without filtration. The results of this study extended our understanding of the behavior and performance of inoculant particles in CFF and their interactions with the inclusions.


Hardness and microstructure homogeneity of pure copper and iron-chromium alloy processed by severe plastic deformation (SPD) were investigated in grain refinement. Equal channel angular pressing (ECAP) is one of the well-known techniques of the SPD technique due to their up-scale ability and other methods. SPD was applied to pure copper and iron-chromium alloy at comparable temperatures up to four passes. The microstructure and microhardness were observed and measured in the transverse plane for each billet. The homogeneity observation was carried out from the sub-surface until in the middle of the billet. The result showed that the deformed structure appeared adequately after the first pass and had a higher hardness level. The first pass showed a higher inhomogeneity factor than the fourth pass due to the homogeneity microstructure. The hardness also showed homogeneous value along the transverse plane, and it was concluded that ECAP could achieve complete homogeneity in grain refinement


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