Subsequent Aging Treatment Research Articles

Microstructure evolution and strengthening mechanisms of electron beam welded 2219 aluminum alloy plate after hot spinning and heat treatment

To investigate the feasibility of spinning the welded aluminum alloys, hot spinning tests were conducted on the electron beam welded (EBWed) 2219 aluminum alloy thick plates at 400 °C and successfully obtained a 2.8 mm curved welded-spun plate with a total thickness reduction of 72 %. The abnormal grain growth (AGG) phenomenon of the base material during hot spinning could be observed due to the reduced pinning effect of the θ-Al2Cu phases and static recrystallization, while the fusion zone exhibited homogeneous recrystallized microstructure. After hot spinning, the yield strength of the base material increased from 89.3 MPa to 133.6 MPa and the yield strength of the joint increased from 93.1 MPa to 134.7 MPa. To further optimize the microstructure and improve the mechanical properties of the spun alloy, the subsequent solid solution and aging treatment were conducted. Most of the coarse θ particles dissolved into the matrix and a large quantity of needle-like θ′ precipitates were generated. The yield strengths of the base material and the joint increased to 213.1 MPa and 216.4 MPa, respectively, which was mainly attributed to the precipitation strengthening of the θ′ precipitates. The comparison between the calculated yield stress and the experimental results showed that the contributions of different strengthening mechanisms in strengths were reliable.

Effect of Process Condition and Test Environment on Tensile Properties in Cold-Rolled Al-Cu-Mg Alloys

Severe plastic deformation processing and subsequent aging treatment have been known to be effective for achieving higher strength than the conventional aging treatment in aluminum alloys. This study prepared the Al-Cu-Mg-based alloy sample, Al-5.3Cu-2.8Mg (mass%). The alloys were solution treated at 480, 495 and 505°C, and cold-rolled by 90%. The effect of process condition and test environment on tensile properties in cold-rolled Al-Cu-Mg alloys was investigated. Results confirm that strength and ductility were improved with increasing the solution heat treatment temperature regardless of test environment. 0.2% proof stress and ultimate tensile strength were higher than aging treatment specimens, but elongation to failure was lower than aged one. Hydrogen embrittlement susceptibility increased with increasing solution treatment temperature. Ductile fracture with many dimples is observed in both cold-rolled and aged specimens. Second-phase particles were observed at the bottom of the dimples. There was no significant difference in fracture surface between the different test environments.

Enhanced Mechanical Properties of Cast Cu-10 wt%Fe Alloy via Single-Pass Friction Stir Processing

In this study, Cu-10 wt% Fe alloy in as-cast state was modified using friction stir processing (FSP). The microstructure evolution of Cu-10 wt% Fe alloys in different states was characterized in detail using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that due to dynamic recrystallization, the FSPed Cu-10 wt% Fe alloy obtained a uniformly equiaxed ultrafine microstructure with low density of dislocation, high proportion of high-angle grain boundaries (HAGBs), and high degree of recrystallization. Fine equiaxed grains with an average size of 0.6 μm were produced after FSP. Many fine-precipitate Fe-phases with an average size of 20 nm were uniformly distributed in the Cu matrix. The FSPed samples possessed excellent mechanical properties, such as high Vickers hardness (163.5 HV), ultimate tensile strength (538.5 MPa), and good elongation (16%). This single-pass FSP method does not require subsequent aging treatment and provides a simple and efficient way to improve the properties of Cu-Fe alloys.

Controlling mechanical properties and energy absorption in AlSi10Mg lattice structures through solution and aging heat treatments

The use of Selective Laser Melting (SLM) has gained popularity due to its ability to produce complex-shaped parts, which includes lightweight lattice structures that are appealing to a variety of industries. AlSi10Mg alloy is a favored choice for SLM due to its excellent specific properties. The utilization of AlSi10Mg in lattice structures further reduces their mass while enhancing specific mechanical properties. However, the inherent brittle deformation behavior of as-built AlSi10Mg restricts the energy absorption potential of lattice structures. This study explores the control of mechanical properties and energy absorption in AlSi10Mg lattice structures and bulk tensile samples through solution and aging heat treatments, examining their impact on microstructural transformations. The results show that solution heat treatment decreases the mechanical properties of lattice structures and bulk tensile samples while improving their ductility and energy absorption. This change is attributed to the transformation of the alloy's fine cellular microstructure into coarser Si-precipitates. Subsequent aging treatments lead to increased mechanical properties in lattice structures solution heat treated at 500 and 550 °C, albeit with a slight reduction in energy absorption. Intriguingly, lattice structures heat treated at 460 °C exhibit unchanged mechanical properties and energy absorption, as confirmed by the t-test. Additionally, the absence of the Al5FeSi intermetallic phase suggests that aging did not occur following solution heat treatment at 460 °C. These findings offer valuable insights into manipulating the mechanical properties and energy absorption of AlSi10Mg lattice structures through controlled heat treatments. Such control can significantly enhance the performance and functionality of lattice structures in practical applications.

Enhanced strength-ductility synergy of laser powder bed fused Inconel 718 via tailoring grain structure and precipitates

Inconel 718 fabricated by laser-powder bed fusion (L-PBF) exhibits a hierarchical microstructure, rendering traditional standard heat treatment processes not entirely suitable. To enhance the tensile properties, a novel heat treatment strategy to simultaneously tailor the grain structure and precipitates of L-PBFed Inconel 718 is proposed. This study aims to investigate the effects of homogenization time, coupled with water cooling, on grain structure, precipitation, and room-temperature tensile properties. The results demonstrate that increasing the homogenization time from 1 h to 4 h results in a significant improvement of tensile ductility by 33.7%, while maintaining higher tensile strength compared to the wrought counterparts. The utilization of water cooling following homogenization effectively suppresses the formation of undesirable δ phases and promotes the precipitation of γ′′ phases during subsequent aging treatment, leading to exceptional tensile strength. Furthermore, the prolonged homogenization time facilitates recrystallization and promotes uniform deformation between adjacent grains, thereby enhancing the material's ductility. This study provides theoretical guidance for the development of customized heat treatment processes to achieve superior mechanical properties in additive-manufactured metallic materials.

Optimization in strength-ductility of Mg-Gd-Y-Zn-Zr alloy processed by upsetting-extrusion combined with intermediate thermo-mechanical treatment (ITMT)

In this work, the effects of intermediate annealing and intermediate annealing subsequent aging treatment on the second phase precipitation, dynamic recrystallization (DRX) behavior, and mechanical properties of Mg-9Gd-4Y–2Zn-0.5Zr (wt.%) alloy were comparatively studied. The results showed that the one-pass upsetting-extrusion (UE) deformation intermediate annealing treatment sample (UAE) exhibited the highest dynamic recrystallized (DRXed) grains number fraction and the largest average DRXed grain size, which was mainly attributed to the precipitation of a large number of β-Mg5RE phases (>1 μm) at the grain boundaries (GBs) and within unDRXed grains after annealing treatment. These β-Mg5RE phases promoted DRX through particle-stimulated nucleation (PSN) mechanism during subsequent extrusion process. However, the lack of the pinning effect of the fine second phase precipitations led to the growth of DRXed grains. The DRXed grains of the deformation intermediate annealing subsequent peak-aging treatment sample (UAAE) were significantly smaller than the UAE sample. This is mainly due to the fact that the densely distributed prismatic β′ phases precipitated by the peak-aging treatment were rapidly transformed into nano-scale β-Mg5RE phases and pinned at the DRXed grain boundaries to inhibit the growth of the DRXed grains during the subsequent extrusion process. The ultimate tensile strength (UTS) and failure elongation (EL) of the UAAE sample were 274 MPa and 14.3%, respectively, 4.2% and 85.7% higher than those of the UE sample, showing excellent strength-ductility synergy. The randomly oriented fine DRXed grains, coarse unDRXed grains with high-density dislocations and substructures, and nano-scale β-Mg5RE particles were co-contribute to the strength-ductility synergy.

Effect of cold rolling on aging precipitation and mechanical properties of magnesium-aluminum alloy

Although magnesium-aluminum alloys, such as AZ80 and AZ91 have promising application potential in automotive, high-speed train and aerospace fields, their age-hardening response is generally not very appreciable. In this work, the aging-hardening response of AZ80 alloy was effectively enhanced by applying cold-rolling deformation before conducting conventional aging treatment at 200 °C. Compared to the directly aged sample, the yield strength of the pre-rolling and aged sample was increased by 35 MPa. Electron microscope examination confirmed that profuse {101¯1} and {101¯1}-{101¯2} twins, consisting of high density of dislocations and stacking faults, were generated by cold rolling. Blocky or ellipsoidal Mg17Al12 precipitates formed at the twin boundaries (TBs) during subsequent aging treatment. Crystallographic analysis indicated that the precipitates at {101¯1} TBs always held an identical Potter OR with both the matrix and twin, while the precipitates at {101¯1}-{101¯2} TBs exhibited three different ORs: Burgers OR, Potter OR and P-S OR with either the matrix or the twin. Moreover, recrystallized grains were found inside {101¯1}-{101¯2} double twins after peak-aging at 200 °C, implying that precipitation and recrystallization might occur concurrently along TBs at a relatively low temperature. It was speculated that the highly stored energy inside twins and the high elastic energy between the precipitates and twins were driving factors for the occurrence of recrystallization.

Enhancing the strength and conductivity of commercialized Cu-Cr-Zr plate through simple high strain cold rolling and aging

Plastic deformation usually improves the strength of Cu alloys by introducing high density dislocations and refined grains, but inevitably reducing electrical conductivity and ductility. Here we demonstrate that three exclusive properties, i.e., strength, conductivity, and ductility can be simultaneously enhanced in commercialized Cu-Cr-Zr plates through the well-controlled thermomechanical treatment. Very high strain cold rolling with a thickness reduction of 98% is applied, resulting in the formation of ultra-fine lamellar structures with an average size of 146 nm, which contributes to high tensile strength of 643 MPa. However, the elongation and electrical properties are poor. The subsequent aging treatment at a low temperature of 400 °C for 5 h introduces high density coherent Cr precipitates in those lamellar structures, while keeping the lamellar thickness almost unchanged. The aged Cu-Cr-Zr alloy exhibit high strength of 592 MPa, high conductivity of 86.8% IACS, and adequate elongation of 15.5%. This work proposes a strategy of overcoming the strength-ductility and strength-conductivity trade-off relationships in industrial Cu products through the balanced manipulation of grain morphology and grain interior precipitation.

Comparative study on microstructure and mechanical properties of a novel nano-composite strengthening heat-resistant steel and two typical heat-resistant steels

In this study, a new nano-composite strengthening austenitic heat-resistant steel designed for ultra-super critical (USC) thermal power plants was analyzed in comparison with the traditional H3RC and S30432 heat-resistant steels to assess its reliability. The microstructure, precipitates, hardness, tensile property and low cycle fatigue behaviors of the three steels at room temperature and service temperature were characterized. The results show that the SP2215 has finer grains, higher twin density, more primary MX, NbCrN and M23C6 precipitates compared with the HR3C and S30432 steels. The main precipitates in the steels after solution treatment are secondary (Nb, V)(C, N) phase (MX). The subsequent aging treatment of the SP2215 steel results in precipitation of the M23C6 carbides at the grain boundaries and Cu-rich phase inside the grains. As a result, the SP2215 steel shows higher Vickers hardness, tensile and fatigue strength (400 MPa) at room temperature than the other two steels. Transgranular fracture is the dominant tensile fracture mechanism of the three steels at room temperature, while intergranular cracking becomes the main fracture mode at high temperature due to precipitation of the continuous M23C6 at the grain boundaries. At the temperature of 700 ºC, fatigue strength of the SP2215 under a peak stress lower than 450 MPa decreases only a little.

Effect of forging pretreatment on the microstructures and mechanical properties of the Al-Cu-Li alloy

The 2195 Al-Cu-Li alloy is widely utilized in the aerospace industry due to its lightweight nature and high strength. Consequently, gaining a comprehensive understanding of techniques to enhance its microstructural and mechanical properties is crucial for the consistent production of reliable and high-strength aerospace components. In this investigation, a pristine 2195 industrial ingot was subject to three distinct forging pretreatments: PT1, which involved a direct three upsetting and three stretching (3U3S) process; PT2, which combined double stage homogenization (DH) with 3U3S; and PT3, which involved DH along with six upsetting and six stretching (6U6S). Subsequent warm deformation and T8 aging treatment were applied to the pretreated forgings. The microstructure evolution during the processes and the final mechanical properties in three orthogonal dimensions were examined. The findings revealed that the combination of DH and multi-dimensional forging (MDF) facilitated the dissolution of non-equilibrium phases to a greater extent. Consequently, the main strengthening phase transformed from the T1 + δ` phase observed in PT1 to the denser T1 + little θ` phase observed in PT2 and PT3 after T8 aging treatment. Notably, the tensile strength and yield strength of PT2 and PT3 specimens increased by 20–30 MPa in all three directions. Moreover, the MDF process accelerated the recrystallization behavior from PT1 to PT3, resulting in a gradual reduction in the average grain size of the pretreated samples from 356 µm to 186 µm. Following warm forging and T8 aging, the grains exhibited a finer and equiaxed structure. Additionally, the coarse phase was identified as the primary source of transgranular cracking. The coarse phases within the matrix became more homogeneous and finer from PT1 to PT3, with a gradual decrease in their area fraction. On the fracture surfaces, the aggregation of coarse phases diminished. Consequently, the elongation in the z-direction improved, and the elongation anisotropy and standard deviation decreased in all three directions for PT3 specimens. The findings presented in this study provide valuable insights into the high-performance manufacturing of Al-Cu-Li alloys.

Enhanced age-hardening of an Al–5Mg–2Zn–1Cu alloy by pre-aging combined with pre-straining

In this work, the synergistic effect of pre-aging and pre-straining on the enhanced age-hardening response of an Al–5Mg–2Zn–1Cu alloy has been systematically investigated using high-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). After pre-aging, only Guinier Preston (GP) zones uniformly distribute in the α-Al matrix. Moreover, dislocations induced by pre-straining can promote the nucleation and growth of T″ and T′ precipitates. With the synergy of pre-aging (80 °C/5 h) and pre-straining (∼4%) treatments, the alloy after second-aging at 130 °C for 12 h exhibits a giant increase of yield strength (∼182 MPa) in comparison to the as-solutionized alloy, reaching ∼348 MPa. The above results show that pre-aging and pre-straining are effective in accelerating the hardening response of Al–Mg–Zn–Cu alloys. Especially, this extraordinary age-hardening response depends strongly on the high number density and uniform distribution of the GP zones induced by pre-straining, acting as preferential nucleation sites for T″ phase and T′ phases during subsequent aging treatment. In addition, it proves that pre-aging and pre-straining can effectively control the precipitation free zones (PFZs) size, relieving the strain concentration in PFZs and improving the comprehensive mechanical properties.

Microstructures and Mechanical Properties of Al-Zn-Mg-Cu Alloys under Multi-Directional Severe Strain and Aging.

Microstructure is a significant factor that influences the mechanical properties of alloys. The effect of multiaxial forging (MAF) and subsequent aging treatment on the precipitated phases of Al-Zn-Mg-Cu alloy remains unclear. Therefore, an Al-Zn-Mg-Cu alloy was processed by means of solid solution and aging treatment, and MAF and aging treatment in this work, and the composition and distribution of precipitated phases were characterized in detail. The MAF results for dislocation multiplication and grain refinement were found. The high density of dislocation greatly accelerates the nucleation and growth of precipitated phases. Thus, the GP-zones almost transform into precipitated phases during subsequent aging. The MAF and aging alloy has more precipitated phases than the solid solution and aging treated alloy. The precipitates on the grain boundary are coarse and discontinuously distributed due to dislocation and grain boundary promoting the nucleation, growth and coarsening of the precipitates. The hardness, strength, ductility and microstructures of the alloy have been studied. Without compromising the ductility much, the MAF and aging alloy has higher hardness and strength, with values of 202 HV and 606 MPa, respectively, and an appreciable ductility of 16.2%.

Effect of twin assisted precipitation on the microstructure and mechanical properties of gradient structure Mg-Gd-Zn-Zr alloy

Nano-precipitation can effectively pin the dislocations and inhibit the dislocations’ motion, making precipitation strengthening one of the most crucial strengthening mechanisms in magnesium (Mg) alloys. Consequently, controlling the segregation of elements at the coherent interfaces to induce the phase precipitation, has become an innovative way of designing Mg alloys. In this study, a novel twin-precipitation composite gradient structure GZ151K (Mg-15Gd-1Zn-0.4Zr) alloy was prepared using ultrasonic surface rolling process (USRP) and heat treatment. The results indicated that the USRP-treated samples subjected to aging treatment demonstrated high thermal stability without significant twin degradation. Additionally, the twin boundaries and grain boundaries could act as the nucleated points for the (Mg, Zn)5Gd phases during the subsequent aging treatment, and further formed the twin-precipitation composite gradient structure. This unique composite gradient structure of alloys treated by USRP and aging treatment was caused by an extra promotion-precipitation strengthening mechanism. Under the effects of promotion-precipitation strengthening, strain hardening, and precipitation strengthening, the mechanical properties of the GZ151K alloy were significantly improved.

Rapid drop in ductility of the bimodal-structured Mg–15Gd binary alloy during early aging

A bimodal-structured Mg–15Gd binary alloy with 45% volume fraction of elongated grains and 55% of dynamically recrystallized (DRXed) grains is fabricated by the extrusion process. The precipitating behavior correlating with the evolution of mechanical properties is systematically characterized during the subsequent aging treatment at 200 °C. The extruded alloy presents an outstanding strength with tensile yield strength of 466 MPa and ultimate tensile strength of 500 MPa at peak aging condition, while the elongation drops from 9.2% in extrusion state to 3.1%. It is found there obviously exist a rapidly decreasing range of ductility at the early stage of aging. Just during this time, the nano precipitates form preferentially at lamellar dislocation boundaries (LDBs) within the elongated grains, but there is no dense and uniform precipitation in the matrix. The results suggest that the low elongation in the aged Mg–15Gd alloy is mainly attributed to the nano precipitates prior formed at the LDBs with a high density in the elongated grains. The related mechanism has been clarified.

Microstructure and mechanical properties of laser-assisted epitaxial growth of nickel-based single crystal superalloys

The effects of process parameters on the microstructures and properties of the laser-assisted epitaxial growth layer are of great significance for the repair of nickel-based single-crystal blades. This work investigated the microstructures and properties of the epitaxial-growth laser-assisted nickel-based single-crystal superalloy. The effects of scanning path, laser power, scanning velocity and heat treatment on the microstructures and hardness of the laser-assisted epitaxial growth layer were explored. The microstructures of the epitaxial-growth samples are the same, starting from the bottom with a continuous columnar dendrite. The dendrites transform into isoaxial crystals when growing to a certain height. The scanning path, laser power, and scanning velocity mutually influence the sample's microstructures. The columnar crystal structure is very stable. Even the epitaxial-growth layer undergoes post-heat treatment, while the isoaxial crystal structure would be coarsened and the hardness decreases, but the subsequent aging treatment leads to an increase in hardness. These findings will greatly help improve the repair effect of single-crystal superalloys.

Effect and mechanism of room temperature rolling, cryogenic rolling and heat treatment on mechanical properties and electrical conductivity of Cu-Ni-Si alloy with continuous directional solidification

Simultaneously improving the mechanical and electrical conductivity of copper alloys has become an important challenge. In this paper, columnar crystal Cu-Ni-Si alloy materials were prepared using continuous unidirectional solidification method, and the effects of room temperature rolling (RTR), cryogenic rolling (CR) and subsequent aging treatment on the microstructure, mechanical and electrical properties of C70250 copper alloy were investigated. The results show that the material has good tensile strength (886 MPa), elongation after break (5.2%) and electrical conductivity (42.4% IACS) when the columnar crystal C70250 copper alloy is cryogenic rolled with 95% depression rate and aged at 450 °C for 1 h. After severe rolling deformation, both RTR and CR C70250 copper alloy produce uniform fibrous structure. Large deformation CR can exhibit higher dislocation density compared with RTR C70250 copper alloy, high lattice distortion results in the transformation of the matrix into an amorphous structure, which has a very strong promotion effect on solute atom diffusion and recrystallization. The precipitation of the fine Ni2Si cluster phase with average size of ∼3.2 nm can be accelerated in a shorter aging time compared to RTR, while the uniform fibrous structure after CR can rapidly recrystallize to produce uniform ultra-fine grains with diameter of ∼550 nm. The strength of the cryogenic rolling alloy can significantly increase through precipitation strengthening, fine grain strengthening and dislocation strengthening. This provides a feasible strategy to improve the overall performance of Cu-Ni-Si alloys.

Effect of post-heat treatments on the microstructure, martensitic transformation and functional performance of EBF3-fabricated NiTi shape memory alloy

In the present work, a single solution treatment as well as solution/aging treatments were employed to regulate the precipitation behavior, martensitic transformation, mechanical and functional properties of EBF3-fabricated NiTi shape memory alloys. Under the optimized post-process heat treatment conditions, i.e., solution treatment at 1000 oC for 10 h followed by subsequent aging treatment at 500 oC for 4 h, the previously existing elongated Ti4Ni2Ox oxides were partially dissolved and interrupted into granular form and relatively uniformly distributed in the NiTi matrix. Meanwhile, the preexisting nanoscale Ni4Ti3 precipitates gradually transformed from clustered or segregated granular to a lenticular shape with the increase of the aging time. The martensite transformation routes also underwent an accompanying alteration, which changed from a one-step (B2-A ↔ B19’-M) to two-step (B2-A → R → B19’-M) transformation. Moreover, Ni4Ti3 precipitated with a coherent relationship of {123} <111>B2-A //{11–20} <0001>Ni4Ti3 which increase the material strength by hindering dislocation movement and improve plasticity by providing a transition domain for accommodating deformation at the interface. The superelastic stability and narrow response hysteresis promoted by the presence of the R-phase are affected by residual (100) compound twins martensite in the NiTi matrix and the permanent plastic deformation activated in (011) [001] slip system of the B2-A phase. This deteriorates the superelastic recovery ratio from 83.6 to 57.4%, as observed after 10 loading-unloading cycles. The post-heat treatment regime presented in the current investigation can be used to modulate the material precipitation, phase transformation, as well as the mechanical and functional properties of EBF3-fabricated NiTi alloys. These results allow to extrapolate the potential for carefully selected post-heat treatment scheduled for additively manufacturing NiTi shape memory alloys.

Effect of multi-pass cooling compression and subsequent heat treatment on microstructural and mechanical evolution of TC4 alloys

Three passes of hot compression tests of hot isostatic pressed Ti-6Al-4V alloys are carried out on a Gleeble-1500D thermo-mechanical simulator with a temperature-drop of 950–900-850 °C, constant strain rate of 0.01∼1 s−1, and the height reduction from 20% to 70%. Then, the subsequent solution and aging treatments are conducted on a heat treatment furnace. The corresponding results of microstructures and mechanical properties show: In the process of multi-pass deformation, dynamic recrystallization with spheroidization of lamellar α phases are the main characteristics affecting flow behaviors. With the increasing strain, lamellar α phases gradually transform from a bimodal distribution to a single peak state perpendicular to the compression direction. The decreasing length and rising thickness of lamellar α phases in the transformation process facilitate the formation of spheroidized α phases. During the heat treatment, the proportion of spheroidized α phases increases, and the spheroidization phenomenon promotes the reduction of lamellar α phases in length and increment in thickness. Lamellar α phases mainly dominate the contribution of microhardness in the hot compression process, and the equiaxed α phases and β transformation structures are combined to influence the mechanical properties of heat-treated Ti-6Al-4V alloys. Notably, β transformation structures contribute primarily at a higher solution temperature.

Enhanced creep resistance in Mg-Y-Nd alloy via regulating prior thermo-mechanical treatment

In this study, the tensile creep behavior of a hot-rolled Mg-4Y-3.5Nd alloy subjected to different prior thermo-mechanical treatments was investigated at 220 ℃. Five groups of samples were prepared using different combinations of the solid solution (S), aging treatment at 220 ℃ for 30 h (A), and hot compression at 490 ℃ to a true strain of 0.25 (C). The abbreviations for the samples are S, SA, SC, SAC, and SCA. Upon examining the yield strength and creep resistance, it was found that creep resistance could not be directly predicted by the yield strength. The stability of the deformation bands (DBs) induced by prior thermo-mechanical treatment plays an important role in determining the creep resistance. The dislocation of the DBs and demonstrated the best creep resistance in the SAC sample, which were prepared using a solid solution, aging treatment, and subsequent hot compression. However, despite the highest yield strength, frequent dislocation motions destroyed the stability of the DBs and deteriorated the creep resistance of the SCA sample, which were prepared using a solid solution, hot compression, and subsequent aging treatment. Among the thermo-mechanical treatments used in this study, the application of aging treatment was important to obtain the resultant creep resistance. When the aging treatment was performed prior to hot compression, the creep resistance could be further enhanced based only on hot compression. Accordingly, the sequence from the strongest to the weakest creep resistance was SAC > SC > S > SCA > SA.

Simultaneous Improvement of Strength, Ductility and Damping Capacity of Single β-Phase Mg–Li–Al–Zn Alloys

Body-centered cubic (BCC) Mg–Li alloy can be effectively strengthened by with the addition of Al and Zn. However, adding excessive amounts result in reduced mechanical properties and damping capacity of the alloy during subsequent heat treatment and deformation. The effects of solution-hot rolling-aging on the mechanical properties and damping capacity of LAZ1333 alloy and LAZ1366 alloy were studied. The solid solution strengthening greatly increases the hardness of the alloy, but the ductility is extremely poor. The AlLi softening phase precipitated during the subsequent hot rolling and aging process greatly improves the ductility of the alloy, but the excess precipitation of in the AlLi softening phase and the solid solution of excess Zn element are not conducive to the substantial improvement of the strength and ductility of the alloy. Excessive addition of alloying elements is detrimental to the damping capacity of the alloy, but the damping capacity of the alloy can be significantly improved by depleting the number of solute atoms through subsequent ageing treatments. The UTS and FE of as-cast LAZ 1333 alloy are 111 MPa and 16.9%, respectively. The as-aged LAZ1333 alloy has the best mechanical properties and damping capacity, and the UTS and FE are increased by 65.8% and 89.3%, respectively, compared to the as-cast alloy, and the damping capacity increased from 0.011 to 0.015.