Influence of surface liquid segregation on corrosion behavior of semi-solid metal high pressure die cast aluminium alloys

Masuku, E.P.; Möller, Heinrich; Curle, Ulyate Andries; Pistorius, Petrus Christiaan; Li, W.

doi:10.1016/s1003-6326(10)60591-2

Cited by 22 publications

(10 citation statements)

References 16 publications

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“…Analyzing the damage by scanning electron microscopy, it is noted that the α globules appear almost not to have been attacked, while the Si particles and the intermetallic compounds in the eutectic have a fundamental role in the corrosion damage [113,116], acting as local cathodes ( Figure 14). Interestingly, some authors have also investigated the effect of surface eutectic segregation on corrosion resistance [117,118]. This thin layer of liquid phase can be found in semi-solid products due to the "sponge" effect [11], when the slurry is injected under pressure into the die, and it contains a higher amount of alloying elements than the bulk.…”

Section: Corrosion Resistancementioning

confidence: 99%

“…Again, the intermetallic compounds were shown to exhibit a cathodic behavior as compared to the α-phase [120]. Interestingly, some authors have also investigated the effect of surface eutectic segregation on corrosion resistance [117,118]. This thin layer of liquid phase can be found in semi-solid products due to the "sponge" effect [11], when the slurry is injected under pressure into the die, and it contains a higher amount of alloying elements than the bulk.…”

Section: Corrosion Resistancementioning

confidence: 99%

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Microstructure and Properties of Semi-Solid Aluminum Alloys: A Literature Review

Pola

Tocci

Kapranos

2018

Metals

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Semi-solid processing of aluminum alloys is a well-known manufacturing technique able to combine high production rates with parts quality, resulting in high performance and reasonable component costs. The advantages offered by semi-solid processing are due to the shear thinning behavior of the thixotropic slurries during the mold filling. This is related to the microstructure of these slurries consisting of solid, nondendritic, near-globular primary particles surrounded by a liquid matrix. This paper presents a review on the formation of this nondendritic microstructure, reports on the different proposed mechanisms that might be responsible, and illustrates the relationship between microstructure and properties, in particular, tensility, fatigue, wear, and corrosion resistance.fraction. Unfortunately, all these tend to increase the production costs [8], even though recent investigations have shown that SSM processing is only slightly more expensive than conventional die-casting and cheaper than some other competing foundry processes [9].Since its development in the early 1970s at MIT [10], much research has been performed worldwide, aimed mainly at developing new and alternative routes of feedstock production for different alloys suitable for SSM processing. At present, there are a number of different techniques used to produce semi-solid castings, differentiated by the percentage of liquid/solid fraction they employ and the way they produce the alloy in the semi-solid state. SSM methods can be divided in two main categories according to their processing route, known as rheocasting and thixocasting [11]. In rheocasting, the semi-solid slurry is prepared in situ from the liquid state down to a certain percentage of solid fraction (usually between 10 and 30% [12]), and then directly transferred into the shot sleeve for being injected into the die. In thixocasting, a billet, characterized by an almost globular or rosette-like microstructure developed through some specific route, is reheated in the mushy zone (semi-solid region) to an appropriately chosen solid fraction (usually between 50% and 60% [13]), placed in a modified shot sleeve and finally injected into the die [14]. Another classification methodology distinguishes the SSM methods according to the initial step used for obtaining the semi-solid feedstock, i.e., from the liquid state, by controlled solidification or from the solid state, via heavy plastic deformation and recrystallization [11].Some of the most common routes for feedstock material preparation are: mechanical stirring, such as the SSR [15,16] or GISS [17] processes, electromagnetic stirring (EMS or MHD) [18,19], ultrasonic stirring (UTS) [20,21], New Rheocasting (NRC or UBE) [22,23], cooling slope [24], twin screw [25], Rheometal [26], liquid mixing method [27], SEED [28], thermomechanical [29], and SIMA [14,30].A number of interesting reviews about the different technologies available for obtaining nondendritic slurries can be found in the literature [11,13,14,[31][32][33]. Nevertheless, indep...

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Section: Corrosion Resistancementioning

confidence: 99%

Section: Corrosion Resistancementioning

confidence: 99%

Microstructure and Properties of Semi-Solid Aluminum Alloys: A Literature Review

Pola

Tocci

Kapranos

2018

Metals

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“…However, the aggregation of the primary α(Al) grains at the inner gate increases the mold filling resistance for the subsequent semi-solid slurry; thus, the number of primary α(Al) grains per unit area and the solid fraction both decrease. By contrast, large primary α(Al) grains are sheared and broken under the pressure shearing; at the same time, mutual impact and friction among primary α(Al) grains occur during mold filling, resulting in the primary α(Al) grains getting refined and spheroidized [28].…”

Section: Microstructures Of the Spiral Samplesmentioning

confidence: 99%

Investigation of rheo-diecasting mold filling of semi-solid A380 aluminum alloy slurry

Liu

Mao

Wang

et al. 2017

Int J Miner Metall Mater

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Abstract:The rheo-diecasting mold filling capacity and the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the mold filling capacity was strengthened with increasing pouring temperature or increasing injection pressure. Under certain process parameters, the mold cavity was fully filled. However, the mold filling capacity decreased with increasing holding time. The mold filling capacity was improved with increasing shape factor of primary α(Al) grains; however, the solid fraction and the grain size significantly increased at the same time. In addition, the microstructures along the route of the spiral samples obviously differed. The grain size decreased gradually from the near-end to the far-end, whereas the shape factor increased gradually.

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“…It is expected that the effect of the surface liquid segregation layer will have an impact on corrosion properties of castings. Pitting was investigated for an Al-Si-Mg alloy [40] while corrosion was investigated for Cu-containing wrought alloy systems [41]. A corrosion comparison of HPDC and R-HPDC magnesium alloys is presented at this conference [42].…”

Section: Component Productionmentioning

confidence: 99%

R-HPDC in South Africa

Curle¹,

Möller²,

Govender³

2012

SSP

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Abstract. The history of semi-solid metal forming and in particular rheo-high pressure die casting at the Council for Scientific and Industrial Research in South Africa is discussed. Processing flexibility is demonstrated on the Al-Si-Mg, Al-Mg-Si, Al-Cu-Mg and Al-Zn-Mg-Cu casting and wrought alloy systems as well as on high purity aluminium, unmodified Al-Si binary eutectic, metal matrix composites and magnesium alloys. Material properties are highlighted.

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Influence of surface liquid segregation on corrosion behavior of semi-solid metal high pressure die cast aluminium alloys

Cited by 22 publications

References 16 publications

Microstructure and Properties of Semi-Solid Aluminum Alloys: A Literature Review

Microstructure and Properties of Semi-Solid Aluminum Alloys: A Literature Review

Investigation of rheo-diecasting mold filling of semi-solid A380 aluminum alloy slurry

R-HPDC in South Africa

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