Enhanced Creep Resistance Research Articles

Controlled creep resistance and melt-flow properties of vitrimers in a facile dual-catalytic system

Interest in vitrimers has increased due to the growing importance of recyclable thermosets. Controlling the flow properties of vitrimers to enhance creep resistance and processability presents challenges, particularly in extending the operating temperature range. Herein, a facile approach using a dual-catalytic system with varied activation energies (Ea) was applied to control the creep and flow properties of vitrimers. We employed an asymmetric dual-catalytic system, where a catalyst with a lower Ea facilitated the formation of a highly cross-linked structure, ensuring high creep resistance at low temperatures, while a catalyst with a higher Ea increased the deformation rate at elevated temperatures. The temperature range with distinct stress-relaxation behaviors were observed when the proper asymmetric dual-catalytic system was applied, where creep was effectively suppressed at lower temperatures, and a dormant catalyst with a higher Ea significantly accelerated the exchange reaction upon activation at higher temperatures. These findings and characterization offer valuable insights into the potential for vitrimer properties control, and vitrimer recycling using diverse catalytic systems.

Enhancing Creep Resistance of Powder-Metallurgy Near-β Titanium Alloy via Rapid Heat Treatment Followed by Aging

Enhancing Creep Resistance of Powder-Metallurgy Near-β Titanium Alloy via Rapid Heat Treatment Followed by Aging

Enhanced creep resistance and microstructure in 7055 Al alloy by in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr)

This work put forward a novel approach to enhancing high-temperature creep resistance of 7055 Al alloy via inducing reinforcements including in-situ (Al2O3 + ZrB2) nanoparticles and Al3(Er, Zr). Creep steady-state rates of the (Al2O3 + ZrB2)/7055 Al composites enhanced by synergistic Er, Zr were lower than the (Al2O3 + ZrB2)/7055 Al composites, indicating the values of stress component (n) and apparent activation energy (Q) were 1.05–1.15 and 1.06–1.08 times of (Al2O3 + ZrB2)/7055 Al composites. The dislocation climb mechanism was considered as the dominative creep mechanism because the suitable true stress exponent was 5. The uniform distribution of Al2O3 and Al3(Er, Zr) and their influence on improving the distribution of ZrB2 aggregates gave rise to relative uniform deformation during creep process. The built interface models that induce Al3(Er, Zr) between the nanoparticle/Al interface could lead to a more thermodynamically stable and well-bonded interface. The coupling effect of attachments containing Al2O3, ZrB2 and Al3(Er, Zr) played an enhanced role in terms of vacancy-trapping, precipitate-nucleation, dislocation motion during creep process. The nanoparticles and Al3(Er, Zr) together with nuclear sites containing solute atoms, vacancies and misfits nearby, caused an expansion-inhibiting effect on the helical dislocations. The in-grain misorientation axes (IGMA) concentration of some deformed grains associated with Schmid factor (SF) analysis were related to 〈001〉, 〈111〉 and 〈101〉 direction. The calculation of creep resistance mechanisms was quantified. Additionally, typical intergranular fracture appeared within the composites due to the relatively uniform reinforcements, resulting in the complex crack path.

Accelerated discovery of lead-free solder alloys with enhanced creep resistance via complementary machine learning strategy

Minor alloying is an effective method to improve the performance of lead-free solder alloys. In this study, we propose a complementary Machine Learning (ML) strategy for minor alloying to design solder alloys with enhanced creep resistance. Two ML models, leveraging compositional and knowledge-aware features, respectively, were constructed to predict the creep stress exponent of Sn–Ag–Cu (SAC)-based solder alloys. Five new solder alloys were designed and experimentally evaluated by screening the virtual sample space consisting of the critical elements, including Bi, In, and Ni, affecting the creep resistance of SAC solder alloys with the ML model. The creep resistance of the designed alloys was characterized using nanoindentation tests. Notably, the creep stress exponent of SAC387-3 wt % Bi-0.4 wt% Ni was determined to be 12.82 at room temperature, indicating a significant 33.9% decrease in creep strain rate compared to the SAC387 alloy. This study demonstrates the potential of the ML approach to design solder alloys with enhanced creep resistance.

Co-, Ni- and Fe-rich grain-boundary phases enhance creep resistance in θ′-strengthened Al-Cu alloys

Microstructural evolution and creep response were investigated in the cast Al-5.0Cu-0.3Mn-0.2Zr (wt.%) alloy with and without addition of slow-diffusing, intermetallic-forming elements Fe, Ni, or Co. Baseline Al-5.0Cu-0.3Mn-0.2Zr alloy exhibits high creep resistance at 300 °C, up to ∼75 MPa, which is attributed to high-aspect-ratio, intragranular θ′-Al2Cu precipitates that effectively suppress dislocation climb. However, θ′-Al2Cu precipitate-free zones form along grain boundaries upon heat treatment, whose extent is amplified during subsequent creep. Such weak regions experience dislocation creep, leading to strain localization and acceleration of grain-boundary sliding. Adding Ni and Co, individually or in combination, leads to the formation of grain-boundary precipitates (Al9Co2, Al3Ni2) which are resistant to coarsening, thus suppressing the formation of θ′-Al2Cu precipitate-free zones. This microstructure provides high creep resistance at stresses up to 75–80 MPa, with strain rates much lower than in unmodified Al-5.0Cu-0.3Mn-0.2Zr. Adding Fe, which results in extensive decoration of grain boundaries with coarsening-resistant Al7Cu2Fe, and then increasing the Cu content to compensate for the Cu loss to this new phase, leads to a new Al-7.4Cu-1.6Fe-0.3Mn-0.2Zr alloy with creep resistance at 300 °C that surpasses known cast aluminum alloys. Adding Fe to improve the creep resistance of Al-Cu alloys is both cost-effective and sustainable. Our findings offer guidelines applicable to various alloy systems on controlling the evolution of precipitate-free zones and its ensuing effects on creep deformation.

Understanding the influence of boron in additively manufactured GammaPrint®-700 CoNi-based superalloy

Boron is commonly added to superalloys in small amounts to enhance creep resistance, but can lead to cracking at high concentrations, especially during the additive manufacturing process. Two variants of CoNi-based GammaPrint®-700 superalloy with different B contents (0.08 at% vs 0.16 at%) were printed via laser powder bed fusion (LPBF) with the same printing parameters, with only the high B alloy exhibiting solidification cracking. Atom probe tomography (APT) revealed stronger segregation behaviors in the high B alloy compared to the low B alloy at both the inter-dendritic regions and grain boundaries (GBs). The segregation behavior at inter-dendritic regions was well captured with Scheil simulation and can correlate with the existing cracking susceptibility index (CSI) on cracking tendencies, although high angle GBs are where cracking occurs according to electron backscatter diffraction (EBSD) measurements. Additionally, the extent of GB segregation was compared between the high B and low B alloy. Higher B additions led to significantly more GB B segregation in the high B alloy compared to the low B alloy. For the high B alloy, the cracked region of one GB exhibited higher levels of B compared to the uncracked region of the same GB. However, much higher B contents were also found in two other uncracked GBs in the high B alloy, which demonstrates that higher GB B concentrations are not fully responsible for the cracking. A much larger variance in GB B segregation content was found in the high B alloy compared to the low B alloy. These phenomena were explained with a solidification model with the GB segregation content expressed explicitly by a modified Langmuir-McLean equation. This model linked the GB segregation content with solidification undercooling, which can be used as quantitative cracking criteria for future builds.

Enhancing creep resistance performance in silica-based ceramic core materials through shell-core structure

The creep behavior of silica-based ceramic cores significantly impacts dimensional precision in investment casting. This study focuses on synthesizing an alumina coating on fused silica surfaces to create a shell-core structure. The creep behavior of silica-based ceramic cores was explored. Specifically, the influence of the shell-core structure on their creep mechanism was investigated. The results revealed the excellent creep resistance of silica-based ceramic cores with shell-core structures. The softening deformation of particles and the viscous flow of the glass phase were observed to account for the differences in creep behavior. The alumina shell structure reinforced the powders, effectively inhibiting the softening deformation of the core structure. Notably, the shell-core structure not only suppressed the viscous flow of the glass phase, thereby weaking the pore filling process, but also promoted the mullitization reaction. This reaction accelerated the consumption of the glass phase, enhancing the creep resistance of the silica-based ceramic cores.

Grain refinement and exceptional creep resistance achieved in an as-cast Mg–Y alloy with Al addition

Grain refinement strengthening is crucial for Mg alloys. However, refined grains can facilitate grain boundary migration during high-temperature creep, usually unfavorably affecting high-temperature creep properties. Al was incorporated into Mg–Y alloy to address this trade-off between fine-grained structures and creep properties, causing the refinement of the Mg–Y alloy (average grain size of 73.2 ± 2.9 μm) while maintaining excellent creep resistance. At 300 °C/50 MPa, the Al-refined alloy exhibited the minimum creep rate of 1.31 × 10−8 s−1, representing a 62 % reduction compared to that of the Mg–Y alloy without Al refinement. During high-temperature creep, the thermally stable Al2Y and long-period stacking ordered (LPSO)/stacking faults (SFs) phases introduced by Al addition effectively pin grain boundaries and impede dislocation movement, which could thus enhance the alloy's creep resistance. Meanwhile, Al addition reduces stacking fault energy (SFE), rendering dislocation climb more challenging and further enhancing the alloy's creep resistance. This study employs Al to refine Mg–Y alloys, achieving grain refinement while enhancing creep resistance, providing a novel method for developing Mg-RE alloys with both refined grains and creep resistance.

Impact of Vanadium Presence on the Mechanical and Microstructural Characteristics of a Dilute Al–Sc–Zr–Si Alloy During Isothermal Aging

In this work, we studied precipitation tendency and resulting ambient and elevated temperature properties in low-V (Al-0.06Sc-0.06Zr-0.18Si-0.05V at.%), high-V (Al-0.06Sc-0.06Zr-0.18Si-0.10V at.%), and free-V (Al-0.06Sc-0.06Zr-0.18Si at.%) alloys subjected to isothermal aging at 300 °C and 400 °C. Scanning transmission electron microscopy revealed that V incorporated into Al3(Sc, Zr) nano-precipitates during aging, forming Al3(Sc, Zr, V) while retaining the spherical morphology and L12 order. Analysis showed that V delays precipitation kinetics by interacting with vacancies, requiring longer aging for peak strength. Both V alloys demonstrated increased peak microhardness around 50–100 MPa relative to the free-V alloy after extended aging. V also reduced precipitate coarsening rates during overaging. However, creep testing exhibited no improvements to threshold stress, indicating V did not expand the precipitate/matrix lattice mismatch needed for enhanced creep resistance. The threshold stress changed from 10.2 MPa in the free-V alloy to 10.4 MPa and 10.1 MPa in the low-V and high-V alloys, respectively. Instead, V localization in the interface of nano-precipitates with matrix contributed more stability. The precipitation strengthening mechanisms in all alloys were studied using established models for L12-reinforced systems. The results showed that coherency and ordering strengthening are the primary active mechanisms.

Unexpected effects on creep resistance of an extruded Mg-Bi alloy by Zn and Ca co-addition: Experimental studies and first-principles calculations

In the present work, a new Mg-Bi based alloy is developed by the addition of Zn and Ca in equivalent atom fraction with Bi. Mg-Bi and Mg-Bi-Zn-Ca alloys were prepared by extrusion at a ram speed of 20 mm/s. Room temperature mechanical properties and creep behaviors at 423 K were investigated. The results show that Zn and Ca co-addition shows little influence on average grain size and texture intensity but changes the dispersive Mg3Bi2 into Mg2Bi2Ca particles in different sizes and a lower density. Twinning is largely activated during room-temperature deformation. Consequently, a slightly decreased proof strength but tripled elongation is shown at room temperature. Unexpectedly, large enhancement in creep resistance is detected after the co-alloying of Zn and Ca and the minimum creep rate is reduced by 10 to 20 times in the BZX621 alloy. Stress exponent n = 4–5 indicates that the creep is a dislocation-climb controlled type. Post-mortem characterization on microstructure shows slip of dislocation 〈c + a〉 are also largely found in B6 as well as BZX621 alloy and cross-slip is detected more severe in B6 alloy. Dynamic segregation and precipitation are also seen in both alloys. Bi-clusters are seen dispersive across the grains in B6 and so did the PFZs that could undermine creep resistance at the grain boundaries. By contrast, Zn-rich needle-like precipitates are developed at most “ends” of 〈c + a〉 dislocations, which would hinder the further dislocation motions and thus improve the creep resistance. First-principles calculations were adopted and the results show that the thermal stability and thermomechanical properties of Mg2Bi2Ca are much better than that of Mg3Bi2. Stacking faults energy is lowered down with the co-addition of Ca and Zn, which could inhibit the rate of dislocation climb and cross-slip. As a result, the improved creep resistance is obtained in the Mg-Bi-Zn-Ca alloys. Microstructural and controlling mechanism changes by thermal activation result in the unexpected enhancement in creep resistance with decreased room-temperature proof strength after co-addition. These findings could contribute to the development and optimization of creep-resistant Mg alloys in the future.

Variations in γ′ formers and refractory elements for enhanced creep resistance and phase stability of an advanced Ni-based superalloy

The strong demands on increasing fuel efficiency have continuously driven the optimization of superalloys for high-performance applications.

Critical effect of exchangeable units distribution on properties of vitrimers: Quantitatively controlling dynamics thus suppressing creep

Vitrimers usually exhibit reprocessability and recyclability due to the reversible crosslinking bonds, thus these materials are expected to be applied as sustainable materials. However, the vitrimer elastomers are susceptible to creep because of their inherent exchange nature, which limits their practical application. The key to improve the creep resistance at service temperature relies on controlling and regulating the intrinsic dynamic properties. Therefore, an in-depth study of the effect of molecular variables on dynamic properties was useful for the design and application of vitrimers. exchangeable units distribution is one of the major molecular variables to tune the dynamics, but it has hardly been studied. Herein, vitrimer elastomers with different uneven degrees of exchangeable units distribution (n) was prepared to study the quantitative relationship between exchangeable units distribution and dynamic behaviors. Due to the uneven exchangeable units distribution, the crosslink-rich and crosslink-poor regions existed simultaneously in networks. The relaxation time of resulting networks increased and then decreased with n due to the combined effects, and samples with moderate uneven distribution showed the longest relaxation time. At the same time, the relaxation times for all samples were short enough to reprocess at elevated temperatures. What is more, the activation energy (Ea) and topology freezing transition temperature (Tv), two important intrinsic parameters for controlling the dynamics, increased linearly with n values. In the meantime, the creep strains and creep rates decreased with n, revealing improved creep resistance. This work provides a strategy to control the dynamics by adjusting the exchangeable units distribution thus enhancing creep resistance. And the proposed strategy and resulting quantitative models might be applied to other vitrimers, which could be utilized to prepare desired vitrimers with exact network designs for various applications.

Microstructural evolution of Mg–14Gd–0.4Zr alloy during compressive creep

The present work reports the creep behavior and microstructural evolution of the sand-cast Mg–14Gd–0.4Zr alloy (wt.%) prepared by the differential pressure casting machine. Their compressive creep tests at 250 °C were performed under various applied stresses (i.e., 60, 80 and 100 MPa). Among them, the sand-cast Mg–14Gd–0.4Zr samples examined under 250 °C/80 MPa for 39 and 95 h, respectively, were chosen to systemically analyze their creep mechanisms using high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). The obtained results showed that the enhancement of creep resistance can be mainly attributed to the coherent β' and β'F phases with an alternate distribution, effectively impeding the basal <a> dislocations movement. However, with the creep time increasing, the fine β'+β'F precipitate chains coarsened and transformed to semi-coherent β1 phase and even to large incoherent β phase (surrounded by precipitate-free areas) in grain interiors. The precipitate-free zones (PFZs) at grain boundaries (GBs) were formed, and they could expand during creep deformation. Apart from the main cross-slip of basal and prismatic <a> dislocations, <c + a> type dislocations were activated and tended to distribute near the GBs. The aforementioned phenomena induced the stress concentrations, consequently leading to the increment of the creep strain.

Elucidating the role of precipitated phase particles in modifying creep properties of as-cast Mg-Bi/Sn-based alloys

The study developed the three alloy systems with different precipitates and examined the role of precipitated phase particles in modifying the creep properties of as-cast Mg-10Bi-0.5Mn-0.5Ag (BMQ1000), Mg-5Bi-5Sn-0.5Mn-0.5Ag (BTMQ5500) and Mg-10Sn-0.5Mn-0.5Ag (TMQ1000) alloys at temperatures ranging from 423 to 473 K and stresses of 45–85 MPa. The values of n for the BMQ1000, BTMQ5500, and TMQ1000 alloys were determined as 6.67, 5.75, and 5.92, respectively. Moreover, the activation energy for these alloys was found to be 164.71, 134.68, and 135.93 kJ/mol, respectively. The results suggested that the creep properties followed the order of BTMQ5500 > TMQ1000 > BMQ1000. A coarse and uneven distribution of the Mg3Bi2 precipitated phase in the BMQ1000 alloy leads to a feeble pining effect on dislocation slipping and generates substantial stress concentrations. For TMQ1000 alloy, while the nanoscale Mg2Sn precipitates have a stronger barrier effect on dislocations than the Mg3Bi2 in the BMQ1000 alloy, their ability to inhibit dislocation climbing is comparatively weak. Furthermore, it was found that Mg2Sn precipitates and α-Mg exhibited a preferential orientation relationship of (020)Mg2Sn // (–1010)Mg, and the morphology of the precipitated phase transformed in a way that hinders dislocation movement effectively. In addition, elastic interactions between the precipitated phases are identified. The above-mentioned factors are largely responsible for the notable enhancement in creep resistance. Further, it is ascertained that cross-slip and pyramidal 〈c + a〉 slip are primary creep mechanisms in the BMQ1000 alloy. In contrast, the dominant mechanisms in TMQ1000 and BTMQ5500 alloys are dislocation climb and pyramidal 〈c + a〉 slip. Moreover, stacking faults (SFs) and twinning assist in the creep deformation of the BTMQ5500 alloy.

Influence of minor RE addition on microstructures, tensile properties, and creep resistance in a die-cast Mg–Al–Ca–Mn alloy

In this work, we have investigated the influence of RE content on the tensile property, creep resistance, and microstructures of a die-cast Mg–9Al-0.3Ca-0.2Mn (wt. %). Minor content of RE elements simultaneously increases the strength and ductility, which is mostly since RE addition refined primary dendritic α-Mg and eutectic α-Mg matrix and eutectic β-Mg17Al12 phases and formed thermally stable Al11RE3 phases. The 0.6% RE adding alloy obtains the best strength-ductility synergy along with the UTS of 245 MPa, TYS of 170 MPa, and EL of 5.7%. The 0.6−1.0% RE addition gives rise to a reduction of the minimum creep rate by over one order of magnitude of the alloy, indicating a significant enhancement in creep resistance, which can be mainly attributed to RE addition introducing Al11RE3 phases to prevent grain boundary sliding, and suppressing dynamic precipitation of γ-Mg17Al12 phases during high-temperature creep. These results can provide important references for the design of creep-resistant die-cast Mg alloys and promote the application of commercial Mg–Al based alloys at high temperatures.

Internal hydrogen bonding of imines to control and enhance the dynamic mechanical properties of covalent adaptable networks

Covalent Adaptable Networks (CANs) have the potential to replace current thermoset materials, as the dynamic covalent bonds in CANs enable reprocessability and recycling of crosslinked polymer networks. A current limitation of CANs is, however, that they are generally susceptible towards creep, as the bond exchange reactions facilitate stress relaxation. In this work, we propose the use of internal hydrogen bonding in polyimine CANs as an efficient tool to enhance creep resistance (at operating temperature) and further control the dynamic mechanical properties, while still enabling malleability at elevated temperatures. We are able to show on a small-molecule level that ortho-substituted hydroxy groups on aromatic imines stabilise the dynamic covalent imine bonds as a result of the internal hydrogen bond that is formed between the hydroxy and imine group. Furthermore, we show that polyimine CANs with incorporated ortho hydroxy groups have significantly enhanced material properties, as can be seen in the glass transition temperature (Tg), elastic modulus (G’), creep resistance and solvent resistance. While we also consider additional steric and electronic effects that might have arisen due to installation of the hydroxy groups, we find that the stabilising effect of the internal hydrogen bond is primarily dictating the material performance.

Creep-induced redistribution of alloying elements in CZ1 zirconium alloys

Introducing minor alloying elements is an effective strategy to improve the corrosion and mechanical properties of zirconium alloys for nuclear applications. During in-reactor service, external environment and stress can affect the distribution of alloying elements, substantially changing the degradation process of zirconium alloys. To date, there is a lack of in-depth understanding of the interaction between creep and microchemistry changes. Here, we conducted systematic transmission electron microscopy (TEM) and atom probe tomography (APT) investigations to address creep-induced redistribution of alloying elements in CZ1 (Zr-Sn-Nb-Fe-Cr-Cu) zirconium alloy with different initial microstructures. Nb, Fe, Sn, and Cu are found to co-segregate at grain boundaries. The higher the intermediate annealing temperature, the larger the Gibbsian interfacial excesses of solute elements are. We further demonstrate that creep can reduce the excess value of Fe at grain boundaries due to the coarsening of Zr-Fe-Cr second phase particles via grain boundary and dislocation pipe diffusion. At the same time, the excess value of Sn is increased by diffusing from the matrix to grain boundaries. Moreover, Cu as a minor element in the concentration range of 0.05–0.3 wt.% is found to segregate at dislocations to form the Cottrell atmosphere and develop Cu-rich nanoclusters for suppressing dislocation motion. The new understanding of the segregation and clustering of minor alloying elements provides guidance for developing zirconium alloys with enhanced creep resistance.

Microstructure and creep properties of cast hypereutectic Al-11Ce alloy with Si addition

This study systematically investigated the as-cast microstructure, heat and creep- resistance of Al-11Ce-xSi (x = 0, 0.9, 1.7 wt%) alloys. A tetragonal AlCeSi intermetallic compound was formed by adding Si. With the increase of Si content, the Chinese-script Al11Ce3/α-Al eutectics changed to rod-like structure and were gradually replaced by broad flaky AlCeSi/α-Al eutectics. The Al-11Ce alloy containing 0.9 wt% Si possessed the optimal tensile properties with an ultimate tensile strength of 129.2 MPa and an elongation of 4.3%, which were 8.4% and 65.4% higher than that of the based alloy, respectively. After aging at 400 ℃ for 1008 h, the microhardness of Si-containing alloys remained unchanged, indicating excellent coarsening resistance of the strengthening AlCeSi phases. Under tensile creep conditions at 300 ℃, the creep deformation of three alloys was the dislocation creep mechanism. Nevertheless, with the addition of 1.7 wt% Si, the steady-state strain rate of Al-11Ce alloy was decreased to 1/3 of its original value. The enhanced creep resistance was mainly attributed to the relatively high volume fraction of intermetallic phase, the reduced volume fraction of coarse primary phase, and the presence of AlCeSi precipitates that effectively hinder dislocations motion.

Effect of dislocation-induced aging precipitate bands on creep resistance of Mg-Gd-Y-Zr-Ag alloy

This work investigates the effect of dislocation array induced β’ precipitation bands on the creep behavior in wrought Mg-8.9Gd-1.8Y-0.5Zr-0.2Ag (wt%) alloy. The alloy with β’ precipitate bands shows significantly enhanced creep resistance ranging from 448 to 548 K. Pipe diffusion-controlled grain boundary sliding (GBS) is suggested to be the main steady creep mechanism below 498 K. Cross-slip is suggested to be the main steady creep mechanism above 498 K. The characterization indicates that the precipitate bands separate the matrix into multiple units within the grains and restrict the long-distance slip of the dislocations. Bands with high thermal stability limit the diffusion of vacancies across the grain and prevent precipitation free zone (PFZ) broadening on the grain boundaries. For the alloy without precipitate bands, basal slip is initiated before the formation of β’, and it is easy to form broad PFZs on grain boundaries. Although cross-slip is still unavoidable at 523 K, these results provide guidance for improving the creep resistance of the deformed Mg-Gd series alloys.

Critical role of dynamic precipitation on enhanced creep resistance in Mg–Zn alloy by Mn substitution for Zr

Mg alloys with excellent creep resistance are able to withstand fatigue and damage under high temperature and complex load. Adding alloying elements rather than rare earth elements, such as Mn, can further reduce the cost and thus facilities the widespread applications of Mg alloys. In this paper, the individual effect of Mn and Zr elements on the dynamic microstructural evolution of Mg–Zn alloys during creep is evaluated, on the basis of identical initial microstructure before creep. And the essential origin of Mn substitution for Zr improving the creep resistance of Mg–Zn alloys by one order of magnitude is revealed. Experimental investigations and first principle calculations reveal that prior-precipitation of α-Mn particles serve as the heterogeneous nucleation sites for the precipitation of β1′ phases, and Mn partitioning in MgZn2 phases promote the nucleation and thermal stability of β1′ precipitates during creep. High number density of fine precipitates can effectively inhibit the occurrence of continuous dynamical recrystallization (CDRX), pin dislocations and impede the activation of cross-slip, which are the main reasons for the enhanced creep resistance in ZM60 alloy. As Zr does not participate in the formation of precipitates in ZK60 alloy, the MgZn2 phases with low thermal stability are prone to growth and coarsening during long-term creep. Large number of fine CDRXed grains and sparse coarse precipitates in ZK60 alloy cannot effectively impede the dislocation movement, which contributes to the occurrence of cross-slip and deteriorate the creep resistance. This work provides new insights for designing and fabricating outstanding heat-resistance Mg alloys.