Hot Tearing Susceptibility Research Articles

Synergistic effect of in situ TiB2 particle and Ti solute on fluidity and hot tearing susceptibility of Al–Li–Cu–X alloy

Synergistic effect of in situ TiB2 particle and Ti solute on fluidity and hot tearing susceptibility of Al–Li–Cu–X alloy

Optimizing hot tearing susceptibility of Al-5.5Zn-2.4 Mg-1.3Cu alloys by grain refinement, increasing mold and casting temperature

The Al-Zn-Mg-Cu alloy is widely used in automotive lightweighting and other applications due to its excellent mechanical properties. However, when this alloy is cast using metal molds, it exhibits high hot tearing susceptibility (HTS), increasing the risk of use. Volumetric shrinkage due to density differences during the transition from liquid to solid metal produces shrinkage stresses. At the same time, lacks feeding of the remaining liquid phase in the late solidification stage can also lead to hot tearing. The purpose of this paper is to present a device for quantitatively determining and optimizing HTS. The relationship between solidification shrinkage displacement and stress was tested in a quantitative way using a Self-designed T-tester equipped with stress and displacement sensors. The test results show that the reduction of grain size shifts the solidification shrinkage of the alloy and reduces the solidification shrinkage stress, which avoids hot tearing caused by higher solidification shrinkage stress and local stress inhomogeneity. Secondly, the grain size reduction increases the number of feeding channels in the solidification vulnerable stage, and more liquid phase is available for crack healing. In addition, the influence of casting process parameters on the HTS was studied.

Effect of Ca on hot tearing susceptibility of WE43 alloy

The effect of Ca on the hot tearing susceptibility (HTS) of WE43 alloy was systematically investigated in this study. The results revealed a significant reduction in HTS with the addition of Ca. The tear volume in WE43-xCa alloys (x = 0, 0.5, 1.0, and 2.0 wt%) was accurately quantified using a Micro-CT system, serving as an indicator for HTS. The lowest HTS was observed in the WE43–2.0Ca alloy, associated with the precipitation of a substantial amount of the Mg2Ca phase. The addition of 2.0 wt% Ca significantly promotes the enrichment of rare-earth eutectic and increases the residual liquid eutectic, resulting in complete healing of the hot tear. The highest HTS was observed in the WE43 alloy due to its low residual liquid eutectic fraction and the inevitable presence of Y2O3 inclusion. Additionally, Ca alloying refined grain size and reduced the susceptible freezing range of the alloys, which can reduce the shrinkage strain acting on the grain boundary per unit at the hot spot. Furthermore, the study investigated the unique morphology of the second phase flat interfaces in the healing region of WE43–2.0Ca alloy. Two possibilities for forming the flattened interface and its effect on HTS are inferred.

Revealing the Role of Minor Zn and Zr Element Addition in Hot Tearing Susceptibility of Mg–Gd–Y Alloy

Revealing the Role of Minor Zn and Zr Element Addition in Hot Tearing Susceptibility of Mg–Gd–Y Alloy

Achieving low hot tearing susceptibility in high-strength cast Al–Li alloys: Experimental investigation and simulation assessment

Due to the exceptional low density and high stiffness, cast Al–Li alloys are deemed suitable for structural applications. However, their economic benefits are limited by intolerable hot tearing susceptibility (HTS) during casting. This work aims to optimize alloy compositions that compromise low HTS and good mechanical properties. Six alloys (Alloys 1–6) with potentially high hot tearing resistance were selected by regulating Li, Cu and Mg additions based on the Kou's criterion and ProCAST simulation. Experimental results indicated that in contrast to Alloys 1–4, Alloys 5 & 6 containing higher solute contents show anomalously high HTS, significantly deviating from the predictions. It was further revealed that this phenomenon originates from a variety of Li-rich inclusions formed at interdendritic channels, which lead to strain localization and hinder residual liquid refilling. Then, Alloys 1–4 with low HTS were subjected to a tailored subsequent heat treatment to achieve optimal mechanical properties. Among the tested alloys, Alloys 3 & 4 exhibit comparatively lower ductility attributed to strain accumulation at the interface between coalesced Sʹ-Al2CuMg phases and Al matrix. In comparison, a good combination of strength and ductility (YS = 371 ± 14 MPa, UTS = 456 ± 19 MPa, EL = 2.5 ± 0.1 %) was successfully achieved in Al-2.5Li–2Cu–1Mg-0.15Zr alloy (Alloy 2) due to the synergistic reinforcement of δʹ-Al3Li and T1-Al2CuLi precipitates. Compared to other available cast Al–Li alloys, Alloy 2 possesses better hot tearing resistance while being highly competitive in strength. Our results are anticipated to contribute scientific guidance for developing high-performance cast Al–Li alloys with low HTS.

Development of Low-Pressure Die-Cast Al-Zn-Mg-Cu Alloy Propellers-Part Ⅰ: Hot Tearing Simulations for Alloy Optimization.

Recent advances in the leisure boat industry have spurred demand for improved materials for propeller manufacturing, particularly high-strength aluminum alloys. While traditional Al-Si alloys like A356 are commonly used due to their excellent castability, they have limited mechanical properties. In contrast, 7xxx series alloys (Al-Zn-Mg-Cu based) offer superior mechanical characteristics but present significant casting challenges, including hot-tearing susceptibility (HTS). This study investigates the optimization of 7xxx series aluminum alloys for low-pressure die-casting (LPDC) processes to enhance propeller performance and durability. Using a constrained rod-casting (CRC) method and finite element simulations, we evaluated the HTS of various alloy compositions. The results indicate that increasing Zn and Cu contents generally increase HTS, while a sufficient Mg content of 2 wt.% mitigates this effect. Two optimized quaternary Al-Zn-Mg-Cu alloys with relatively low HTS were selected for LPDC propeller production. Simulation and experimental results demonstrated the effectiveness of the proposed alloy compositions, highlighting the need for further process optimization to prevent hot tearing in high Mg and Cu content alloys.

Effect of Ti Addition on the Hot-Tearing Susceptibility of the AlSi5Cu2Mg Alloy

Effect of Ti Addition on the Hot-Tearing Susceptibility of the AlSi5Cu2Mg Alloy

Effect of Sb Addition on Hot Tearing Susceptibility and Mechanical Properties of Mg–7Al–1Ca–xSb (x = 0, 0.5, 1, 1.5, and 2 wt.%) Alloys

Effect of Sb Addition on Hot Tearing Susceptibility and Mechanical Properties of Mg–7Al–1Ca–xSb (x = 0, 0.5, 1, 1.5, and 2 wt.%) Alloys

Simultaneous improvement of mechanical and castability properties of Al-Cu-Mn based alloys by Ca/Ni micro-alloying

Currently one major barrier for the design of cast high-strength and high-toughness Al alloys is hot tearing. In this work, a strategy of combination of squeeze casting and microalloying (Ca/Ni eutectic elements) in Al-Cu-Mn based alloys was employed to inherit the excellent mechanical properties of Al-Cu alloys whilst simultaneously reducing their tendency to hot tearing. The developed alloys exhibit comparable castability (fluidity and hot tear resistance) to A356, which is widely available commercially. However, their comprehensive mechanical properties far exceed those of A356. Trace Ca/Ni additions markedly reduce the grain size of the alloy and simultaneously increase the fraction of intergranular low melting point eutectic liquid phases, which is beneficial to the improvement of liquid feeding. The fine equiaxed grains have excellent thermal shrinkage coordination, while the high volume fraction eutectic liquid phase delays the development of grain cohesive skeleton. Accordingly, the localized shrinkage stress/strain at the hot spot is released timely, thus inhibiting the emergence and propagation of hot cracks in the brittle solidification interval. The diminished hot tearing susceptibility is attributed to the reduced load onset temperature and load values in the hot spot region. A new intergranular bridging mechanism is discovered in low-Ca alloys: based on compositional segregation-induced nucleation of an intergranular bridging skeleton, which strengthens the intergranular adhesive force and effectively reduces the hot tearing tendency of the alloys. The alloys with high-Ca/Ni additions, however, reduce the hot tearing tendency by healing cracks through eutectic liquid phase backfill. The results of the hot tearing experiments of the developed alloys are analyzed with the current hot tearing evaluation criteria. The results demonstrate that the predictions of the Kou's criterion provide guidelines for the design of alloys that are resistant to hot tearing.

New quaternary eutectic Al-Cu-Ca-Si system for designing precipitation hardening alloys

The aluminum corner of the previously unexplored quaternary eutectic Al-Cu-Ca-Si system promising for the design of new heat treatable alloys have been studied using thermodynamic modeling and experimental techniques. The experimental data have revealed the presence in equilibrium of a previously undescribed quaternary compound identified as a strict stoichiometric Al2CaSiCu phase with a tetragonal I4/mmm structure (Pearson symbol: tI10) and the lattice parameters a = 4.04 Å and c = 11.00 Å. The phase has a density of 3.36 g/cm3 and a microhardness of 335 Hv. In accordance with the suggested structure of the phase diagram, its region that can be promising for the design of heat treatable alloys contains three (Al)+Al2Cu+Al2CaSiCu, (Al)+Al2Si2Ca+Al2CaSiCu and (Al)+Al2Cu+Al2Si2Ca quasi-ternary sections and two (Al)+Al2Cu+Al2Si2Ca+Al2CaSiCu and (Al)+Al2Cu+Al2CaSiCu+Si four-phase fields. Analysis of the precipitation hardening response for the new quaternary Al-5 wt%Cu-Ca-Si alloys suggests that it is not inferior (the obtained peak hardness is ∼125 Hv) to that for the alloys Al-5 wt% Cu (∼120 Hv) and Al-4 wt%Si-5 wt%Cu (∼125 Hv) based on the conventionally used systems. However, to obtain noticeable hardening at aging, the content of silicon should be at least 1.1–1.2 times higher than that of calcium. A comparative hot tearing susceptibility (HTS) study revealed that the new heat treatable Al-5 wt%Cu-Ca-Si alloys have higher hot tearing resistances (HTS ∼16 mm according to a pencil probe) than that of the Al-5 wt%Cu base alloy (HTS >16 mm).

Semisolid tensile properties near solidus temperature of direct-chill-cast AA5182 alloy and its hot-tearing susceptibility

Semisolid tensile properties near solidus temperature of direct-chill-cast AA5182 alloy and its hot-tearing susceptibility

Influence of zinc and silver additions on hot tearing susceptibility of Mg-14Gd-0.4Zr alloy

The effects of 1Zn and/or 2Ag additions on the hot tearing susceptibility (HTS) of Mg-14Gd-0.4Zr (wt%) alloy were studied. The HTS was evaluated by both theoretical predictions using Kou's criterion and experimental observations based on the in situ force-temperature recorded constrained rod casting (ISFTCRC) method. The results show that the order of HTS from high to low is Mg-14Gd-2Ag–1Zn-0.4Zr, Mg-14Gd-2Ag-0.4Zr, Mg-14Gd-1Zn-0.4Zr and Mg-14Gd-0.4Zr. Adding 1Zn and/or 2Ag changes the solidification path and the solidification interval, which affects the hot tearing susceptibility. Alloying elemental 1Zn slightly increases the solidification interval and the temperature range in the square root of the solid phase fraction (ƒs1/2) range of 0.949–0.995, resulting in a slight increase in the hot tearing susceptibility. The addition of 2Ag drastically widens both the solidification interval and the temperature range in the ƒs1/2 range of 0.949–0.995, thus significantly increasing the hot tearing susceptibility. Compared to the addition of 2Ag alone, the broadening degree of both the solidification interval and the temperature range in the ƒs1/2 range of 0.949–0.995 is greater by adding the composite 2Ag/1Zn, which further promotes the occurrence of hot tearing. A narrower solidification interval and a temperature range in the ƒs1/2 range of 0.949–0.995 result in a lower hot tearing susceptibility.

Hot Tearing Susceptibility and Solidification Behavior of Mg-xGd-(4-x)Y-2Ni-0.5Zr Alloys

The hot tearing susceptibility (HTS) of Mg-xGd-(4-x)Y-2Ni-0.5Zr (x = 0, 1, 2, 3, 4, wt%) alloys was evaluated using a T-shape mold method. When the Gd element increased and the Y element decreased, the HTS of the alloys decreases gradually. The Mg-4Y-2Ni-0.5Zr has the highest while Mg-4Gd-2Ni-0.5Zr has the lowest HTS value. Microstructure observation reveals that the grains of the magnesium alloy were refined to a certain extent when the Gd element increased and the Y element decreased. The ‘pinning’ effect of the LPSO phase precipitated along the grain boundary effectively increases the solid skeleton strength of the alloy and reduces the HTS of the magnesium alloy to a certain extent. The thin and uniform liquid film at the fracture can disperse the solidification shrinkage stress. In addition, the binary phase precipitated in the alloy forms a fast channel of residual liquid phase feeding on the liquid film, which is beneficial to feeding hot cracks. Solidification behavior of the alloys by thermal analysis showed that with the increase of the Gd element and the decrease of the Y element, the dendrite coherency temperature of the dendrites of the alloy decreases, and the residual liquid phase feeding is easier. The solid fraction of dendrite coherency increases, the skeleton strength of the alloy increases, and the HTS of the alloy decrease. In Mg-xGd-(4-x)Y-2Ni-0.5Zr (x = 0, 1, 2, 3, 4, wt%) alloys, when x is 1, 2, 3, 4, the HTS of the alloy is reduced by 25%, 49%, 63%, 81%, respectively compared with that when x is 0.

Evaluation of Horizontal and Vertical Constrained Rod Casting Mold on Hot Tearing Susceptibility of Al-Cu Alloys

Evaluation of Horizontal and Vertical Constrained Rod Casting Mold on Hot Tearing Susceptibility of Al-Cu Alloys

Influence of cooling path on solidification morphology and hot tearing susceptibility of an Al−Cu−Fe−Mg−Si alloy

AbstractIn this work, a numerical approach is applied to study the impact of local cooling conditions on the hot tearing in an aluminium‐copper alloy with iron, magnesium and silicon as impurities. At first, CALPHAD‐coupled multicomponent and multiphase‐field simulations were performed to elucidate the effect of cooling conditions on solidification morphology in the final, critical stage of solidification. Then, the evolution of the melt flow permeability is derived from the simulated three‐dimensional microstructures and discussed in the context of the Rappaz‐Drezet‐Gremaud criterion for hot tearing susceptibility. With increasing cooling rates, the microstructure becomes finer and the resulting permeability first increases and then saturates within the investigated range. It is shown that the Rappaz‐Drezet‐Gremaud hot‐tearing criterion in combination with microstructure simulations responds to different cooling conditions in contrast to a Scheil‐Gulliver based model or an evaluation of the average Kou‐index.

Effects of Fe, Si, Cu, and TiB2 Grain Refiner Amounts on the Hot Tearing Susceptibility of 5083, 6061, and 7075 Aluminum Ingots

Aluminum alloys 5083, 6061, and 7075 are prone to hot tearing under direct-chill casting conditions; the defects that form during solidification of those alloys are highly sensitive to variation in the alloying elements, with these elements commonly being Si, Fe, Cu, and Ti. This study investigates the influence of the morphology, content, and size of intermetallic compounds on the hot tearing behavior of the 5083, 6061, and 7075 aluminum alloys by combining a constrained rod casting technique, phase diagram calculation, and multiscale microstructural characterizations. The fishbone-shaped α-Al15(Fe,Mn)3Si2 in 5083 can serve as a path for crack nucleation and growth, and an increase in Si content results in Mg2Si assuming fishbone morphology, thereby increasing hot tearing susceptibility. The amount of plate-like β-Al5FeSi is the primary factor controlling the hot tearing susceptibility of 6061. For 7075, increasing the Cu content can greatly enhance the remaining liquid fraction, feeding, and hot tearing susceptibility. For all three alloys, TiB2 grain refiner minimizes hot tearing. This study elucidates the influences of the amounts of Fe, Si, Cu, and TiB2 grain refiner on hot tearing susceptibility. The findings can help establish compositional control standards for the 5083, 6061, and 7075 aluminum alloy series, particularly when the recycling rate must be increased.

Computational simulation of hot tearing susceptibility of steel harp casting in rigid fixation conditions

Computational simulation of hot tearing susceptibility of steel harp casting in rigid fixation conditions

Enhanced Mechanical Strength and Electrical Conductivity of Al–Ni‐Based Conductor Cast Alloys Containing Mg and Si

The electrical conductivity (EC), mechanical strength, hot tearing susceptibility (HTS), and related microstructure of Al–xNi–0.55Mg–0.55Si conductor alloys (x = 1–4 wt%) are investigated. Adding Mg and Si into Al–Ni‐based alloys, numerous β″/β′ precipitate after T5 and T6 treatments, thus significantly improving the EC and mechanical strength. The HTS of the alloys reduces significantly as the Ni content increases, mainly because of an increase in the eutectic Al–Al3Ni and a reduction in the grain size. Under T5 condition, the tensile strengths increase gradually with the Ni content and reach a medium strength level, with yield strength (YS) of 158–205 MPa and EC of 47.1–50.7% IACS. After applying T6, all alloys achieve a high strength, with YS of 246–287 MPa and EC of 47.7–51.1% IACS. However, the strength decreases with increasing Ni content. In general, the Al3Ni–0.55Mg–0.55Si alloy presents a better trade‐off among HTS, YS, and EC among the four alloys investigated. Due to its excellent properties (EC of 49.4% IACS and YS of 178 MPa in T5, and EC of 49.7% IACS and YS of 250 MPa in T6), the Al3Ni–0.55Mg–0.55Si alloy is a promising material for the fabrication of Al conductor cast alloys.

Hot Tear Formation During the Casting of Al–Zn Binary Alloys

The hot tearing susceptibility of Al–Zn binary alloys with solute contents of Al–0.5%Zn, Al–1%Zn, Al–2%Zn, and Al–4%Zn, with all compositions being in wt%, is investigated through physical experiments and numerical simulation. The temperature at the hot spot, the designed critical point for hot tearing, and the load at the end of the test bar are measured and compared with the simulation results. The test samples with 0.5 and 1.0% Zn show hot tears while those with 2.0 and 4.0% Zn have no sign of such tearing. The correlation between solid fraction, strain, stress, and hot tearing indicator is revealed using the simulation results of the Al–1%Zn and Al–4%Zn alloys. Just before solidification, the Al–1%Zn alloy is found to have not only a much higher strain rate at the hot spot of the test bar than that of the Al–4%Zn alloy, but also a higher strain gradient along the longitudinal direction. It is believed that both the high strain rate and high strain gradient are attributable to the formation of hot tears in the Al–1%Zn alloy.

Simulating the hot tearing susceptibility of steel cast flange

Simulating the hot tearing susceptibility of steel cast flange