Metallurgical Characterization of Hot Tearing Curves Recorded during Solidification of Magnesium Alloys

Huang, Yuanding; Wang, Z.; Srinivasan, A.; Kainer, Karl Ulrich; Hort, Norbert

doi:10.12693/aphyspola.122.497

Cited by 21 publications

(4 citation statements)

References 10 publications

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“…After hot tears occur, the neighbouring regions have a negative pressure. The negative pressure can suck back the eutectic liquid, and subsequently heal the hot cracks [39]. Liquid healing was reported for Mg-Y and Mg-Gd binary alloys, especially at a high solute content [7,15].…”

Section: Effect Of Zn Additionmentioning

confidence: 99%

Effect of Zn addition on hot tearing behaviour of Mg–0.5Ca–xZn alloys

et al. 2015

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The influence of Zn addition (0, 0.5, 1.5, 4.0 and 6.0 wt. %) on hot tearing behaviour of Mg-0.5 wt.% Ca alloy was investigated using a constrained rod casting (CRC) apparatus. The effects of mould temperature and grain refinement on the hot tearing susceptibility (HTS) were studied. Hot tears were observed with 3D X-ray tomography and the tear volumes were quantified. Results show that the Zn addition increases the HTS of Mg-0.5Ca alloys. At a mould temperature of 250 ⁰C, all alloys investigated except Mg-0.5Ca-6Zn alloy show severe HTS. An increase in the mould temperature from 250 ⁰C to 450 ⁰C did not reduce the HTS in Mg-0.5Ca-1.5Zn and Mg-0.5Ca-4Zn alloys. Among all the investigated alloys, Mg-0.5Ca-4Zn alloy exhibits severe HTS as it completely broke away from the sprue-rod junction. The HTS of alloys was well correlated with the susceptible temperature range (ΔT s). An increase in ΔT s increased the HTS. The hot tears propagated along the grain boundaries through liquid film rupture. Grain refinement by Zr addition improved the hot tearing resistance of Mg-0.5Ca-4Zn alloy as the fine grain structure facilitated the easy feeding of liquid into the last area of solidification and accommodated the developed strain more effectively.

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Section: Effect Of Zn Additionmentioning

confidence: 99%

Effect of Zn addition on hot tearing behaviour of Mg–0.5Ca–xZn alloys

et al. 2015

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“…However, the analysis of the castings (shown in the next section) indicates that hot tearing occurred in this alloy too. In this situation, according to Huang et al [30], the onset of hot tearing can be identified by locating the point at which the load as a function of time changes from linear increment to non-linear increment in the force curve. Hence the initiation temperature of hot tearing for Mg-1.5 wt.% Y alloy is found to be 616.6 °C .…”

Section: Hot Tearing Volume Measurementmentioning

confidence: 99%

Hot tearing susceptibility of binary Mg–Y alloy castings

et al. 2013

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The influence of Y content on the hot tearing susceptibility (HTS) of binary Mg-Y alloys has been predicted using thermodynamic calculations based on Clyne and Davies model. The calculated results are compared with experimental results determined using a constrained rod casting (CRC) apparatus with a load cell and data acquisition system. Both thermodynamic calculations and experimental measurements indicate that the hot tearing susceptibility as a function of Y content follows the " λ " shape. The experimental results show that HTS first increases with increase in Y content, reaches the maximum at about 0.9 wt.% Y and then decreases with further increase the Y content. The maximum susceptibility observed in Mg-0.9 wt.% Y alloy is attributed to its coarsened columnar microstructure, large solidification range and small amount of eutectic at the time of hot tearing. The initiation of hot cracks is monitored during CRC experiments. It corresponds to a drop in load increment on the force curves. The critical solid fractions at which the hot cracks are initiated are in the range from 0.9 to 0.99. It is also found that it decreases with increasing the content of Y. The hot cracks propagate along the dendritic or grain boundaries through the interdendritic separation or tearing of interconnected dendrites. Some of the formed cracks are possible to be healed by the subsequent refilling of the remained liquids.

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“…At last, the eutectic is formed from the last remaining liquid at eutectic temperature and appears as eutectic segregation on the SEM micrograph [37]. Many previous investigations have shown that the eutectic liquid can completely or partially heal the previously formed hot cracks in binary Al-Cu [37,38], Mg-Al, Mg-Zn and Mg-Y alloys [9,39]. In direct chill casting of Al-Cu binary alloys, a thick line of eutectic (or eutectic path) along grain boundaries of several grains is observed near the tear region [37,38].…”

Section: Effect Of Zn Additionmentioning

confidence: 99%

Hot tearing characteristics of Mg–2Ca–xZn alloys

et al. 2015

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Influence of Zn content (0, 0.5, 1.5, 4 and 6 wt%) on the hot tearing characteristics of Mg-2 wt% Ca alloy was investigated. The constrained rod casting (CRC) apparatus equipped with a load cell and data acquisition system was used. The initiation of hot tearing was monitored during solidification. The effect of mould temperatures (250 and 450 • C) on the hot tearing was also investigated. The formed tears were evaluated using X-ray tomography and the tear volumes were measured. Results show that hot tearing susceptibility (HTS) of Mg-2Ca-xZn (x = 0, 0.5, 1.5, 4 and 6 wt%) alloys increases with increase in Zn content up to 1.5 wt%, then decreases with further increase in the Zn content to 6 wt%. Higher initial mould temperature (450 • C) improves the hot tearing resistance. The observations on the microstructures and the fracture surfaces suggest that the hot tear initiated at the grain boundaries and propagated along them through the thin liquid film rupture and liquid metal embrittlement of solid bridges. Tear healing by low melting point eutectic liquid is also observed in some of the alloys.

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Metallurgical Characterization of Hot Tearing Curves Recorded during Solidification of Magnesium Alloys

Cited by 21 publications

References 10 publications

Effect of Zn addition on hot tearing behaviour of Mg–0.5Ca–xZn alloys

Effect of Zn addition on hot tearing behaviour of Mg–0.5Ca–xZn alloys

Hot tearing susceptibility of binary Mg–Y alloy castings

Hot tearing characteristics of Mg–2Ca–xZn alloys

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