Low-temperature Deformation Research Articles

Correlation analysis of creep properties at low temperature between BF reinforced BRA modified asphalt and its mixture

To better understand the low-temperature creep properties of basalt fibre (BF)-reinforced Buton rock asphalt (BRA)-modified asphalt mixture, a rheological test on an asphalt bending beam and a creep test on an asphalt mixture bending beam were performed on the original asphalt (OA), BF-reinforced asphalt (BFA), BRA-modified asphalt (BRAA), BF-reinforced BRA-modified asphalt (BFBRAA), and its mixtures, namely, the OA mixture (OAM), BFA mixture (BFAM), BRAA mixture (BRAAM), and BFBRAA mixture (BFBRAAM). The creep compliance curves of the eight materials were fitted according to the Burgers model, and correlation analysis was conducted on the creep compliance curves of the four groups of materials, namely, OA/OAM, BRAA/BRAAM, BFA/BFAM, and BFBRAA/BFBRAAM. The results showed that as the testing temperature decreased, the creep stiffness modulus of the OA, BRAA, BFA, and BFBRAA increased and the creep rate decreased. Moreover, the failure load values, bending tensile strengths, and stiffness of OAM, BRAAM, BFAM, and BFBRAAM gradually increased while the bending tensile strains gradually decreased, and the creep compliance of OA/OAM, BRAA/BRAAM, BFA/BFAM, and BFBRAA/BFBRAAM decreased. In addition, the test results showed that the addition of BF to asphalt and asphalt mixtures effectively improved their low-temperature deformation properties, whereas the addition of BRA to asphalt and asphalt mixtures led to a decrease in their low-temperature crack resistance. Furthermore, the Burgers model provided a good fit to the creep compliance curves of the eight materials, and a correlation formula of E1, η1, E2, and η2 between asphalt and its mixture at low temperature was established, providing a new perspective and method for analysing the creep characteristics of asphalt mixtures.

Hot deformation behavior and process parameters optimization of GH4738 nickel-based superalloy

The GH4738 nickel-based superalloy exhibits exceptional overall performance at high temperatures. However, its high deformation resistance, narrow hot working window, and complex microstructural evolution pose significant challenges to plastic deformation of the alloy. Hot compression experiments were conducted on the GH4738 nickel-based superalloy using a Gleeble 3800-GTC thermal–mechanical physical simulation system. The hot deformation behavior of the alloy was systematically investigated across deformation temperatures ranging from 950 to 1150 °C and strain rates from 0.01 to 10 s⁻1. The analysis of the true stress–strain curves revealed the effect of deformation parameters on the flow stress of the alloy. The flow stress was highly sensitive to both strain rate and deformation temperature, increasing with higher strain rates or lower deformation temperatures. Based on the experimental data, a high-precision peak stress prediction model and an Arrhenius constitutive model considering strain compensation were established. In addition, processing maps for the alloy were constructed based on the dynamic materials model (DMM) and Prasad's instability criterion. Coupled with microstructural observations and validation, the flow instability of the alloy was manifested as flow localization and adiabatic shear bands (ASBs), while the deformation mechanism in the safe region was characterized by discontinuous dynamic recrystallization (DDRX). Ultimately, the optimal hot working process windows for the alloy were determined to be 1010–1075 °C/0.01–1 s−1 and 1075–1150 °C/0.03–1 s−1.

Research on the ultra-low temperature tensile deformation mechanism of Al-Mg-Si alloys in different heat treatment states

The susceptibility of Al-Mg-Si alloy to cracking during room temperature large plastic deformation poses a significant obstacle to its widespread application. Cryogenic temperature forming of aluminum alloys has emerged as a prominent research topic. However, the precise mechanisms underlying the enhancement of aluminum alloy plasticity in different states remain elusive. In order to elucidate this matter, a series of uniaxial tensile experiments were conducted on Al-Mg-Si alloy featuring diverse initial states, under varying temperature conditions. The results show that when the deformation temperature is reduced from 25℃ to −196℃, the tensile strength and elongation of the wrought material are increased by 48 MPa and 5.42 %, and the tensile strength and elongation of the annealed material are increased by 118 MPa and 5.65 %. In contrast, while the T4 state sample exhibited a significant improvement in tensile strength (103 MPa), no substantial enhancement in elongation was observed. This disparity can be primarily attributed to the absence of second-phase precipitation in the as-forged and annealed states. As the temperature decreased, the critical shear stress increased, resulting in increased resistance to deformation. Consequently, an increased degree of lattice rotation and activation of dislocations in various slip systems ensued, thereby improving the deformation uniformity. The formation of initial microvoids predominantly occurred close to grain boundaries. Therefore, compared with room temperature deformation, low temperature deformation caused by the accumulation of dislocations and hole sprouting concentrated at a single location was less likely. As a result, the dislocation distribution was more uniform and fracture was less likely to occur. Conversely, in the T4 state, the aging process resulted in the precipitation of a substantial amount of the soluble second phase (Mg5Si6). Consequently, microvoid nucleation transpired at the phase boundaries, leading to an elevated tensile strength. However, because of the increased dislocation hindrance when the deformation temperature was lowered, no significant enhancement in plasticity was observed.

Effect of Recycled Asphalt Mixture and Solid Waste-Based Solidification Materials on Performance of Cold-Regenerated Asphalt Mixture

In this study, an aging asphalt mixture was regenerated by a waste-based rejuvenator and cemented by solid waste-based solidification materials (SSMs). A splitting test, wheel tracking test, and three-point bending test were conducted to evaluate the properties of the regenerated asphalt mixture (RAM). The results reveal that the properties of the asphalt mixture were not diminished or were moderately enhanced by the 30% substitution of RAP. With the substitution of RAP to 100%, the splitting tensile strength, dynamic stability, and splitting strength ratio were decreased by 13%, 15%, and 5%, respectively. With the 100% substitution of SSMs for cement, the compressive strength, dynamic stability, flexural strain, and splitting strength ratios of the RAM were increased by 40%, 32%%, 14%, and 8%, respectively. The lightweight components can be supplemented, and low-temperature deformation and interlayer flowability can be improved by the incorporation of the rejuvenator. The generation of hydrated calcium silicate and ettringite for SSMs is greater than those of cement. The massive generation of ettringite has been observed to increase the solid phase volume by 120%, which may facilitate a more complete filling of the remaining pores in the RAM due to water evaporation. The regeneration and cement on green and the high performance of the rejuvenator and the SSM markedly enhanced RAM performance.

Strong Strain Hardening Induced by {11–22} Twins of Hexagonal Titanium upon Low-Temperature Deformation Along the Transverse Direction

Strong Strain Hardening Induced by {11–22} Twins of Hexagonal Titanium upon Low-Temperature Deformation Along the Transverse Direction

Low-temperature superplastic behavior of nanostructured Al-Zn-Mg-Cu alloy

The evolution of Al-Zn-Mg-Cu alloy microstructure during high pressure torsion at room temperature and subsequent low-temperature superplastic deformation is studied. The formation of a nanostructured state in Al-Zn-Mg-Cu alloy made it possible to implement a superplasticity (SP) effect at 170 °C and a strain rate of 5 × 10−4 s−1. The deformation relief of the gauge part of an Al-Zn-Mg-Cu alloy sample at the stage of steady-state SP flow is analyzed. Low-temperature superplastic deformation is stated to take place due to grain boundary sliding. High formability of nanostructured alloy under biaxial tension at a temperature of 170 °C is recorded.

Study of austenite grain growth and recrystallization behavior in pipeline steels containing niobium

Abstract The austenite grain growth and recrystallization behaviors of three pipeline steels with different Nb contents were investigated through reheating and thermal simulation compression experiments. The initiation conditions for dynamic and sub-dynamic recrystallization of austenite were analyzed, and sub-dynamic recrystallization equations in Avrami form were established. The influences of Nb content and deformation conditions on the evolution of grain size during austenite recrystallization was examined. The findings indicate that the austenite grain size of the three steels increases gradually with higher reheating temperatures, while the average grain size decreases with increasing Nb content. Sub-dynamic recrystallization initiation temperatures for the B150-steel, B145-steel, and 73-steel were found to be 920 °C for 10 s, 940 °C for 30 s, and 960 °C for 30 s, respectively. During high-temperature deformation, Nb in solid solution hindered recrystallization by impeding grain boundary and dislocation movement. At lower deformation temperatures, Nb(C, N) precipitation pinned grain boundaries and dislocations and consumed substantial free energy, thus competing with recrystallization. As Nb content increased, strain-induced precipitation became more pronounced, resulting in more effective inhibition of recrystallized grain growth.

Enhancing of low-temperature deformation compatibility of pure titanium welded tube by laser welding and cold-worked in welded zone

This study is aimed to improve the low-temperature deformation behaviour of titanium heat exchange tubes by optimizing welding method and weld treatment processes. The various welding processes and cold-worked in welded zone process are adopted, and the effects of macro-morphology, microstructure and mechanical properties on low-temperature deformation behaviour are studied. The results show that the width of the laser welded joint and welded zone is 3.8 mm and 2.9 mm respectively, which is 40% and 63% of TIG welded joint. Especially, the width of heat affected zone and the grain size of laser welded joint are obviously reduced due to its concentrated energy density. The cold-worked process in welded zone can relieve the macroscopical and microstructural discontinuity between base metal, heat affected zone and welded zone. The inner weld reinforcement is eliminated to improve smooth transition and the columnar α grains in welded zone are remarkable fragmented with plenty of twins. The hardness of the welded zone after cold-worked is significantly higher than that of the base metal, resulting in base metal being the main deformation area of the welded tube at low temperature, which is beneficial to improve the deformation performance of the whole welded tube. By adapting the cold-worked and laser welding process with smooth transition and narrower weld width, the pure titanium welded tube can meet the requirement of three times low-temperature deformations.

Investigating the influence of acid-base/KH550 composite surface modified BF on the properties of fiber-reinforced SBS-modified asphalt mastic

The surface properties of fibers significantly influence fiber-reinforced asphalt mastic (FRAM) performance. However, the impact of composite-modified basalt fiber (BF) on basalt fiber-reinforced asphalt mastic (BFRAM) remains unclear. This study examines the effects of acid-base/KH550 modified BFs on BFRAM performance, providing an experimental basis for further optimization. Tests included SEM and fiber leakage for BFs and separation, physical properties, DSR, and DMA for BFRAMs. The research indicates that (1) Composite modification enhances the fiber’s surface roughness, activity, oil-holding properties, and compatibility with SBS-modified asphalt. (2) Due to differences in acid-base etching, acid etching combined with KH550 promotes a more uniform and extensive coupling reaction with the BFs. In contrast, alkali etching with KH550 facilitates a deeper, localized reaction. (3) Composite modification of the BFs significantly improves the high-temperature rheological properties of the BFRAMs, with acid-base etching making the grafting reaction between the fiber and coupling agent more pronounced. At a test temperature of 82°C, the rutting factor of BFRAMs containing composite-modified (acid-etched + KH550) BFs is 2.7 times that of asphalt mastic without BFs. (4) The glass transition temperature of BFRAMs modified by acid etching and KH550 is 4.9°C lower than that of the original asphalt mastic, proving that composite-modified BFs enhance the low-temperature elastic deformation capacity of the BFRAMs.

Excellent low temperature superplasticity and its deformation mechanism in nano/ultrafine grained Fe–17Cr–6Ni stainless steel

Superplastic deformation typically occurs in non-ferrous metals at high temperatures, which results in severe surface oxidation and high energy consumption. In this study, we designed and manufactured a nano/ultrafine-grained stainless steel with a dual-phase microstructure that exhibits excellent low-temperature superplastic deformation capability. A maximum tensile elongation of approximately 500% was achieved when the tensile test was conducted at 700 °C with an initial strain rate of 5 × 10⁻⁴ s⁻1. Even after a 500% tensile elongation, the austenite grains in the gauge section of the tensile specimen still maintained an equiaxed grain shape, and the texture also weakened significantly, indicating that grain boundary sliding and grain rotation dominated the deformation process during superplastic flow. The outstanding superplasticity is mainly attributed to the dual-phase microstructure composed of nano/ultrafine austenite grains and martensite.

INFLUENCE OF CRYOGENIC COOLING AFTER DRAWING ON CHANGES IN PROPERTIES OF STEEL WIRE

One of the promising and little-studied methods for obtaining an ultrafine-grained structure and enhanced mechanical properties is the so-called cryogenic deformation - deformation at temperatures below 120K. It is assumed that low deformation temperatures suppress recovery processes, thus contributing to the accumulation of an extremely high dislocation density and increase internal stresses, as well as activate deformation twinning, which together will accelerate grain refinement. In this regard, in this work, we studied the drawing of steel wire under cryogenic cooling in liquid nitrogen. The results of the laboratory experiment show that the application of cryogenic deformation treatment after wire drawing improves mechanical properties compared to conventional wire drawing. In this case, after two cycles of deformation, the relative contraction after stretching decreases by 8 %, the ultimate strength increases by 40 %, and the conditional yield strength by 26 %. The results show that the deformation conditions during cryogenicdrawing are an additional factor for the realization of structural resources of steel wire physical and mechanical properties optimizing.

Deformation-induced grain boundary segregation in a powder-metallurgy ultrafine-grained MoNbTaTiV refractory high-entropy alloy

A powder-metallurgy MoNbTaTiV refractory high-entropy alloy synthesized by mechanical alloying (MA) and spark plasma sintering was subjected to hot deformations at different temperatures and strain rates. The microstructural morphologies were characterized, and component element segregation was elucidated. With grain refinement and lattice strain increase, the large inhomogeneous milled powder became refined and homogeneous after the MA. Component element segregation was observed at relatively low deformation temperatures and high strain rates. As the deformation temperature increased and the strain rate decreased, the segregation gradually disappeared, which was attributed to dislocation movement.

Hot compression recrystallization and processing characteristics of 18 %Cr lean duplex stainless steel with Mn addition

The deformation differences of hot compression tests for 18 % Cr lean duplex stainless steels, alloyed with 3.1 and 5.8 wt% Mn concentrations were comparatively investigated. The deformed microstructure revealed that more Mn promoted the formation of austenitic dislocation cells, inhibited the occurrence of dynamic recrystallization (DRX), and resulted in a decrease in the number of refined austenite grains at lower temperatures and strain rates. Meanwhile, more Mn addition promoted ferrite DRX, and delayed austenite DRX initiation deformed at higher strain rates and lower deformation temperatures. The nearly complete refinement of austenite grains formed due to DRX deformation at 950℃/0.01 s−1 with 3.1 % Mn addition, while fine grains caused by ferrite DRX mainly occurred at 850℃/1 s−1 with 5.8 wt% Mn addition. The relationships between the Zener–Hollomon parameter (Z) and critical strain (stress) were established using the power law relation. The stability processing domains with high power efficiency greater than 0.34 narrowed with increasing Mn content, are located in the temperature range of 1000–1150℃ and strain rate range of 0.01–0.03 s−1, and austenite DRX plays a significant role in compression deformation improvement. At a low deformation temperature of 850 ℃, the work hardening rate in the initial strain increased with increasing Mn addition, and a lower strain rate and deformation temperature contributed to the dynamic deformation softening caused by austenite DRX, but ferrite DRX slightly contributed to the improvement of compression deformation. The DRX kinetics models show that the trend of the volume fraction of DRX as a function of processing variables is in good agreement with experimental data.

The dual effects of phosphorus on the hot deformation behavior in an as-cast Ni-Fe-Cr based alloy

The effect of phosphorus on dynamic recrystallization (DRX) and hot deformation behavior of an as-cast Ni-Fe-Cr based was investigated by performing hot compression deformation. The results indicate that phosphorus can play dual roles during hot deformation. The phosphorus dissolving in matrix and segregating to the dislocation can hinder the dislocation motion and DRX nucleation, which acts as the solute drag effect. And phosphorus-addition can increase the size and number of MC carbides. MC carbides increase the local dislocation density around them and promote the DRX nucleation and exhibit the particle stimulated nucleation effect. Influenced by the dual effects of phosphorus, the DRX fraction and grain size decrease first and then increase with the increase of phosphorus content. The solute drag effect of the substitutional phosphorus atoms on dislocation motion decreases the DRX nucleation rate and increase the possibility of instability at low deformation temperature in phosphorus-addition alloys. In the early stage of deformation, more MC carbides in the high-phosphorus alloy hinder the motion of dislocation and result in the stress concentration, which leads to the intergranular cracks at high temperature and high strain rate.

Cryogenic tensile behavior of CoNiCrMo medium entropy alloy

The microstructure and mechanical properties of 35Co-34Cr-24Ni-7Mo medium entropy alloy, known as MP35N, were investigated at different cryogenic temperatures (77 K and 195 K) and compared with those at room temperature (295 K). The microstructural features at the mentioned three distinct temperatures were characterized by X-Ray diffraction, electron back skater diffraction analysis and transmission electron microscopy. It was found that, compared to room temperature, cryogenic temperatures significantly increased the yield strength and tensile strength from 330 MPa and 1300 MPa at 295 K to 711 MPa and 1890 MPa at 77 K, respectively, without a noticeable change in elongation. Microstructural investigation revealed that lower deformation temperatures resulted in higher dislocation density, higher stacking fault probability, more mechanical twins, and a more homogeneous dislocation structure. Up to a strain of 0.4, no sign of fcc to hcp phase transformation was observed in EBSD, TEM images, or SAED patterns, even at 77 K. The higher work hardening due to mechanical twinning, increased dislocation density, and lower stacking fault energy, in addition to a more homogeneous dislocation structure, postponed the formation of geometric instabilities and maintained a ductile fracture mechanism at cryogenic temperatures.

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Pure titanium due to its high corrosion resistance, low stiffness and good mechanical properties is commonly used in medicine for orthopaedic applications. However, its material properties (especially in the case of α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upalpha }$$\\end{document}-titanium) require a further enhancement to fulfil its role. The thermoplastic deformation in mid-temperature is proposed as a method for microstructure improvement. Titanium samples were compressed in different temperatures and strain rates to determine the best conditions for grain fragmentation—the main factor responsible for strength and hardness increase. The thermoplastic stress–strain curves were registered. Then microstructure observations and electron backscatter analysis were performed on the chosen samples. Finally, mechanical response of the previously deformed material was obtained in room temperature compression tests. A significant grain fragmentation was recorded for the material deformed in 400 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\hbox {C}$$\\end{document}, at 0.1/s and 1/s strain rates. Desirable results were also noticed for the deformation performed at 500–600 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\hbox {C}$$\\end{document}. However, high temperatures (700–800 ∘C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{\\circ }\\hbox {C}$$\\end{document}) and strain rates (10/s) resulted in dynamic recrystallization, causing undesirable grain growth. An increase in hardness was observed in all cases, with higher values recorded in lower deformation temperatures. Room temperature compression tests revealed slight increase of ductility.

The improvement of deformability in AA7075 alloy through cryogenic treatment and its correlation with microstructural evolution and FE modelling

Cryogenic treatment has high potential for improving the deformation behavior through the recrystallization at a low temperature. In this work, true stress–strain curves were obtained via compression tests to understand the deformation behavior of an AA7075 under cryogenic conditions. Results showed a significant improvement in the flow stress of AA7075, increasing from 260 to 560 MPa at the yield point. The strain hardening exponent (n) also increased from 0.25 to 0.35 after deformation at cryogenic temperatures. The presence of Al2CuMg phase influenced the deformation texture of the tested aluminum alloy, resulting in more elongated grains and fine sub-grains after deformation at cryogenic temperatures, due to the hindered recrystallization. Microstructure evolution after deformation at room and cryogenic temperatures was investigated using EBSD technique to characterize texture and recrystallized grains. The results indicated that the spacing of the high-angle grain boundaries (HAGBs) in the sample deformed at room temperature was slightly larger than in the cryogenically treated sample. The alloy deformed at the cryogenic temperature exhibited a higher strain hardening exponent (n = 0.35) compared to room temperature deformation (n = 0.25). Furthermore, finite element analysis supported the experimental findings, showing that the Plastic Equivalent Strain (PEEQ) of the model tested at cryogenic temperature was higher than at room temperature, attributed to grain refinement during low-temperature deformation. The calculated effective stress responses at cryogenic temperatures for the investigated flow stress aligned well with the experimental results. These new aspects and mechanisms of deformation of aluminum alloys at cryogenic temperatures can improve the formability of high-strength alloys in the future production of more complex and integrated lightweight components.

Microstructure evolution and recrystallization mechanisms of a fine-grained nickel-based superalloy during thermal deformation process

The thermal deformation behavior of fine-grained GH93 alloy was investigated through isothermal compression tests at deformation temperatures of 930–1020 °C, strain rates of 0.001–1 s−1 and deformation amount of 50 %. Based on the true stress-strain data, the power dissipation maps, instability maps and hot processing maps of this alloy were established at different strains. The precision of the hot processing maps was verified by deformation microstructures, and the optimal processing parameter was ascertained to be 975–1010 °C/0.001–1 s−1. The microstructure evolution, dynamic recrystallization (DRX) and twinning evolution were analyzed by means of EBSD and SEM, simultaneously the DRX mechanisms under different deformation parameters were elucidated. The results demonstrate that the degree of recrystallization increases with the increase of deformation temperatures and the decrease of strain rates. At lower deformation temperatures, γ′ phases at grain boundaries hinder grain boundaries to slip and encourage dislocation entanglement, thereby promoting recrystallization. As the deformation temperatures increase, γ′ phases gradually dissolve, and the pinning effect weakens, leading to grain coarsening. The proportion of ∑3 twin boundaries shows a continuous upward trend with increasing temperature, which is consistent with the trend of changes in recrystallization volume fraction. DRX mechanisms of the alloy under different process parameters include continuous dynamic recrystallization (CDRX) mechanism and discontinuous dynamic recrystallization (DDRX) mechanism. DDRX is the main recrystallization mechanism, and CDRX mechanism becomes more active with increasing temperatures and decreasing strain rates, while it is still only an auxiliary nucleation mechanism.

Influence of preparation parameters on rheological properties and relation analysis of waste rubber modified bitumen mastic

Waste rubber modified bitumen has gained significant attention as a sustainable and innovative material in the field of pavement engineering. This study aims to evaluate the performance of rubber modified bitumen mastic by considering its rheological properties, specifically focusing on preparation parameters, i.e., rubber content, mesh number, and filler to bitumen ratio. From the experimental results, the rheological properties of rubber modified bitumen mastic were significantly influenced by preparation parameters. Increasing the rubber powder content in bitumen mastic results in higher viscosity. Increasing the rubber content improves high-temperature rutting resistance to a certain extent, however, excessive rubber powder content would result in weakened high-temperature performance improvement. The rutting factor decreases gradually with an increase in the rubber mesh number. A ratio of filler to bitumen of 0.95 exhibits the best resistance to rutting at high temperatures. Higher rubber content and larger mesh number correspond to stronger low-temperature crack resistance in bitumen mastic. As the ratio of filler to bitumen increases, the low-temperature deformation capacity gradually decreases, resulting in weaker low-temperature crack resistance. Based on the grey relation analysis, the ratio of filler to bitumen has the greatest impact on the high and low-temperature rheological properties of bitumen mastic, followed by the rubber content. The rubber mesh number has a relatively lower impact. It is crucial to control the ratio of filler to bitumen to avoid excessive values. When possible, a higher rubber powder content should be used while meeting process requirements. These findings provide valuable insights into the design and optimization of rubber modified bitumen mastic, which can contribute to the development of sustainable and high-performance bitumen mixtures, promoting the use of recycled rubber in pavement engineering.

A new pavement crack repair sealant with two-way shape memory effect

To address the challenge of sealant debonding due to cyclic temperature variations, a new pavement crack repair sealant which can achieve two-way shape memory deformation is developed. The developed crack sealant is a shape memory liquid crystal elastomer (SMLCE), designed to exhibit the deformation characteristics of heat contraction and cold expansion. First, the material composition and preparation process of the developed SMLCE are given. Thermodynamic properties, phase transition temperatures and molecular structures are analyzed based on DSC and FITR. The effects of the crosslinker and chain extender ratios and the key preparation processes on the two-way shape memory deformation and mechanical performance of SMLCE are systematically analyzed. Based on the analysis, the optimum ratio of SMLCE is determined to be 1:15 and the optimum secondary crosslinking preparation process is 150% orientation stretching. Under the optimal solution, the developed SMLCE can achieve the multiple two-way shape memory reversible deformation with a maximum 46% deformation in the temperature range of -20°C∼120°C. At the same time, the developed SMLCE has excellent mechanical properties, with a tensile strength of 20.7Mpa and an elongation at break of 322%. It also exhibits good low-temperature deformation capabilities at -10°C and above. Finally, the suitability and application potential of the developed two-way SMLCE as a pavement crack sealant are assessed. The developed SMLCE has good adaptability in most climate zones, which indicates its great potential as a pavement crack sealant. This research provides a new way for the pavement crack repair.