Chao Xu

Harbin Institute of Technology | HIT · Analysis and Measurement Center

Mg-Gd-Y-Mn-Sc alloys with different Mn+Sc contents were prepared by hot extrusion and ageing treatment. The effect of Mn+Sc additions on the microstructures, tensile properties, and corresponding strengthening mechanisms of the as-extruded and peak-aged Mg-Gd-Y-Mn-Sc alloys were systematically investigated. Mn+Sc additions had outstanding grain ref...

A high-performance Mg-8Gd-4Y-0.5Mn-0.2Sc (wt.%) alloy was fabricated by the combination of homogenization, hot extrusion and ageing. The microstructure evolution during the homogenization at 550 °C was investigated, and the optimum time of 18 h was obtained to minimize the volume fraction of second phase particles and to keep fine grain structure....

In this paper, we report the use of cold-sample rolling (CSR) processing, which induced a high fraction of double twins and a substantial texture-weakening effect in an Al-concentrated commercial Mg-6Al-1Zn (mass%) alloy sheet. A CSR-processed and subsequently annealed sheet showed a weak basal texture with a broad distribution of the (0001) poles...

Magnesium matrix composites reinforced with graphene have attracted great attention because of their fascinating properties. However, it is still challenging to realize the effective addition and dispersion of graphene in the Mg matrix. In this work, a novel in-situ liquid metallurgical process that converts CO2 to graphene is developed to fabricat...

Lightweight, high-modulus structural materials are highly desired in many applications like aerospace, automobile and biomedical instruments. As the lightest metallic structural material, magnesium (Mg) has great potential but is limited by its low intrinsic Young's modulus. This paper reviews the investigations on high-modulus Mg-based materials d...

The mechanical properties and processing scale of metal matrix nanocomposites are urgently desirable for engineering application. In this work, a novel production method of graphene nanosheets (GNSs) reinforced magnesium (Mg) matrix nanocomposites was developed by in-situ liquid metallurgy combined with hot extrusion. GNSs were dispersed and modifi...

An extraordinary high-strength dilute Mg-0.8Al-0.1Ca-0.6Mn (wt. %) alloy wire was successfully developed by hot drawing, which exhibits high tensile yield strength of 394 MPa, ultimate tensile strength of 431 MPa and moderate elongation to failure of 6.0%. The high strength was mainly attributed to the ultra-fine dynamically recrystallized (DRXed)...

It is urgent to improve the quality and reduce the cost of graphene for widespread applications. In this work, a simple and cost-effective vapor-liquid reaction route to produce few-layer graphene was developed for the seawater/oil separation. The method can not only achieve direct synthesis of graphene by blowing CO2 bubbles into magnesium (Mg) me...

Constructing graphene/metal layered structure serves as a promising way to solve the strength-toughness trade-off of metallic materials, while the weak interlayer interfaces usually lead to premature failure of the composites. This work focuses on the interfaces of the GNS-MgO/Mg layered composite with ultra-high strengthening and toughening effici...

An anomalous in-plane anisotropy was found in a basal-textured Mg–Al–Zn alloy sheet due to a minor fraction of transverse direction (TD)-orient (0001) poles induced high activation of tensile twinning. This led to deteriorated tensile properties along the TD, emphasizing an importance of microtexture designing for wrought magnesium with high-perfor...

Microstructure evolution and mechanical properties of the as-drawn dilute Mg-0.8Al-0.1Ca-0.6Mn (wt. %) alloy wires during annealing and peak-aging treatment were investigated in this paper. The results show that the high density of nano-sized Al-Mn precipitates strongly hindered grain boundary migration to restrict grain growth during annealing und...

To develop high-performance magnesium alloy sheets for sheet applications in the automotive industry, we investigated the effects of the Al content on the tensile properties, stretch formability, and corrosion resistances of Mg-xAl-0.5Ca-0.4Mn-0.8Zn (mass%, x = 2, 5, 8, AXZMx101) alloy sheets. The addition of 5% Al led to the highest limiting dome...

The effect of 0–1.0 at.% Al additions on grain refinement and phase transformation of the Mg-2.0Gd-1.2Y-0.5Zn-0.2Mn (at.%) alloy containing a long period stacking ordered (LPSO) phase was investigated in this work. The addition of Al promoted the formation of the Al2RE phase in the Mg-2.0Gd-1.2Y-0.5Zn-0.2Mn (at.%) alloy, and the dominant secondary...

The effects of La addition on the microstructure, thermal conductivity and mechanical properties of as-cast and as-extruded Mg-3Al-xLa-0.3Mn (x = 1, 3 and 5 wt.%) alloys were studied. The results showed that the thermal conductivity of the alloys increased with the addition of La element, which was due to the formation of the Al11La3 phases by cons...

A typical layered Al composed of alternating fine-grained layers (FLs) and coarse-grained layers (CLs), fabricated by hot pressing and hot rolling, exhibits a superior strength-ductility synergy under uniaxial tensile loading compared with monolithic Al. The mechanism behind the excellent mechanical properties was elucidated from the perspective of...

The layered structural parameters have been reported to be critical for tuning the tensile properties of laminated metals. Here, we investigated the effects of the thickness ratio (rc/f) of coarse-grained layers (CLs) to fine-grained layers (FLs) on the enhanced ductility of the laminated Al. The local strain evolution demonstrates that the strain...

The effect of homogenization on microstructures and tensile properties in a dilute Mg–Zn–Ca–Mn alloy sheet was investigated. High-temperature homogenization at 480 °C dissolved eutectic intermetallic phases before rolling; however, there was a significant growth of αMn precipitates, resulting in a coarse grain structure in the rolled and annealed a...

An Mg-6Zn-0.3Ca (mass%) alloy sheet with a strong basal texture feature was cold-rolled using a small pass reduction, and the microstructure development during the annealing was tracked by a quasi-in-situ electron backscattered electron analysis. Anomalous double twinning with the (0001) pole being aligned to the transverse direction was formed aft...

Strength and ductility synergy in an Mg-3mass%Al-Mn (AM30) alloy sheet was successfully improved via twin-roll casting and annealing at low-temperature. An AM30 alloy sheet produced by twin-roll casting, homogenization, hot-rolling, and subsequent annealing at 170 °C for 64 h exhibits a good 0.2% proof stress of 170 MPa and a large elongation to fa...

Two-phase titanium aluminides are desirable for a wide range of high-temperature structural applications for their excellent thermo-physical properties. In this paper, a novel laminated TiAl matrix composite (LMC) consisting of alternating equiaxed grain layers (EGLs) and fully-lamellar grain layers (FGLs) has been fabricated successfully by hot-pr...

A novel laminated TiAl matrix composite (LMC) consisting of alternating equiaxed grain layers (EGLs) and fully lamellar grain layers (FGLs) has been fabricated successfully by hot pressing of alternating Ti/Al–6Si foils and subsequent multi-step reaction annealing. The oxidation behavior of the LMC at 800 °C was studied. The results show that the o...

The effect of the rolling temperature on the room-temperature stretch formability, tensile properties, microstructure, and texture of Mg-4.9Al-0.16Mn (mass%) alloy sheet has been investigated. Rolling at 220°C resulted in the formation of a weakly aligned isotropic texture feature, and the annealed sheet showed splitting of (0001) poles to the roll...

Twin-roll-cast Mg-3.07Al-0.25Mn (mass%) alloy was continuously rolled at a warm temperature, and the room-temperature stretch formabilityFormability, tensile properties, microstructures, and texture of the annealed sheets were investigated. The sheet rolled at 220 °C exhibits large Index Erichsen values over 8 mm due to the formation of a ring-like...

Various solution-treatments were applied on a rapidly solidified and subsequently rolled Mg-7.50Al-1.07Ca-0.17Mn (mass%) alloy sheet, and a room-temperature stretch formability, tensile properties, microstructures, and textures of the solution-treated sheets have been investigated. Although the solution-treatment at 400 °C gives high strengths, the...

The yield strength of metals is typically governed by the average grain size through the Hall-Petch relation, and it usually follows the rule of mixture (ROM) for layered composite materials. In the present study, an extraordinarily high yield strength, far beyond the predicted values from the Hall-Petch relation and the ROM, is achieved in a speci...

In this study, an ultra-high yield strength (~417 MPa) and moderate ductility (~12.9%) was obtained in Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy through a method of decreased-temperature multi-directional forging (MDF) processing followed by aging treatment. The ultra-fine grained structure with average grain size of ~0.9 μm was prepared after 6 passes...

This study analyzed the effect of extrusion parameters on the microstructural evolution and tensile properties of a Mg-8.0Gd-4.0Y-1.0Mn-0.4Sc (wt.%) alloy. The variation in the dynamic recrystallization (DRX) and dynamic precipitation behavior of the alloy under different extrusion parameters were investigated in detail, and the DRX behavior during...

The static recrystallization and associated texture evolution were investigated in an extruded Mg-Zn-Gd alloy with bimodal microstructure based on a quasi-in-situ electron back-scatter diffraction (EBSD) method. The typical rare earth (RE) texture formed during annealing, evolving from the bimodal microstructure with [101¯0] basal fiber texture tha...

Effect of Si content on microstructures, tensile properties, and creep properties in a gravity-cast Mg–6Al-0.4Mn–2Ca (wt.%, AMX6042) alloy has been investigated. High content of Si addition increases the ductility of the AMX6042 alloy without large loss of strengths; however, addition of Si over 0.6 wt.% decreases fraction of (Mg,Al)2Ca phases sign...

Effects of trace manganese (Mn) contents (0.1 wt% and 0.3 wt%) on mechanical properties and microstructure of the Mg-5.5Al–3Ca wt.% alloy were systematically investigated. By addition of 0.3 wt% Mn, the yield strength of the as-extruded alloy is significantly increased from 366 MPa to 402 MPa. The as-cast alloys show a dendritic structure consists...

We have successfully developed a Mg–3Al–0.4Mn (wt%) alloy sheet with good room-temperature formability. The alloy sheet shows a large Index Erichsen value of 8.2 mm due to its unique texture feature where the most of the grains have circular distribution of basal poles away from the normal direction of the sheet. The fine grain structure also leads...

Highlights  Forced-air cooling hinders DRX and causes smaller DRXed grain size, stronger basal texture and higher dislocation density.  Forced-air cooling promotes dynamic precipitation and γ′ phases then slightly restricts the precipitation of β′ phases.  3. The extruded alloy with forced-air cooling after peak-ageing treatment shows TYS of 439...

A long-standing question is why layered structures can overcome the strength-ductility trade-off and achieve synergy in this relationship. In this paper, layered Ti/Al, Ti/Ti metal materials are taken as examples to investigate the influence of a heterogeneous layered structure on their deformation behavior from a viewpoint of the local strain. In-...

We have developed a strong Mg–6Zn-0.2Ca (wt.%) based alloy sheet with good room-temperature formability via micro-alloying of Al and Mn. The Al and Mn micro-alloyed Mg–6Zn-0.2Ca-0.1Al-0.1Mn (wt.%, ZXAM6000) alloy sheet forms fine grain structure with an average grain size of 15 μm and weakened basal texture, in which (0001) planes of most grains sp...

The microstructure and mechanical properties of the extruded Mg–2Gd–1.2Y–0.5Zn (at.%) alloy with Mn or Zr addition were investigated. The results show that Zr addition refines the microstructure of the homogenized alloy more efficiently and facilitates the dissolution of the secondary phases in comparison with Mn addition. After extrusion at 400 °C...

This study investigates the effects of extrusion ratio and temperature on the microstructure and mechanical properties of as-extruded Mg-11.5Gd-4.5Y-(1Nd/1.5Zn)-0.3Zr (wt %) alloys. After hot extrusion the studied alloys exhibit a bimodal microstructure consisting of fine dynamic recrystallized (DRXed) grains with relatively random orientations and...

The age-hardening behavior and mechanical properties of the extruded Mg-2Gd-1.2Y-0.5 Zn (at.%) alloy with Zr or Mn additions were investigated. The results show that Mn added alloy exhibits more remarkable age-hardening response than Zr added alloy, which is attributed to the fact that partitioning of Mn into the β phases, β′ precipitates and long...

Synchrotron radiation computed micro-tomography (SR-µCT) is a non-destructive characterization method in materials science, which provides the quantitative reconstruction of a three-dimension (3D) volume image with spatial resolution of sub-micrometer level. The recent progress in brilliance and flux of synchrotron radiation source has enabled the...

In this work, the Mg-8.5Gd-2.5Y-0.3Zr (wt. %) and Mg-8.5Gd-2.5Y-0.5Zn-0.3Zr (wt. %) alloys were subjected to indirect extrusion. The microstructure and mechanical properties of the two alloys were carefully investigated to clarify the effect of trace Zn, in terms of solid solution Zn atoms and γ′ phases, on the Mg-Gd-Y-Zr alloy. The results indicat...

A discontinuous yielding was observed in the as-extruded Mg-7Gd-2Y-1Zn-0.6Zr (wt. %) alloy under uniaxial tension along the extrusion direction, which was eliminated by the peak-aging treatment. The deformation mechanisms of the as-extruded and peak-aged alloys were studied by in-situ synchrotron diffraction measurement and elastic-viscoplastic sel...

In this work, Mg-(5, 6, 7) Al-3Ca-0.3Mn (wt.%) alloys were fabricated by permanent mould direct chill casting followed by indirect extrusion, to achieve ultrahigh strength. The microstructure and mechanical properties of these alloys were systematically investigated. While C36-(Mg, Al)2Ca was identified to be the major eutectic phase in the as-cast...

A Ca-containing Mg-4Zn-1MM(mischmetal)-0.1Ca (wt.%, ZEX4101) alloy sheet shows Index Erichsen value of 6.7 mm, which is better than commercial Mg alloy sheets. The good formability is attributed to its weakened basal texture, in which the intensity of the (0001) poles of the recrystallized grains spreads towards the transverse direction. By monitor...

Abstract The trace addition of rare earth (RE) elements in Mg alloys can modify the extrusion texture, leading to the formation of RE texture and thus improved formability. The interrupted extrusion experiment as well as electron back-scatter diffraction (EBSD) characterization was conducted in Mg-1.5Zn-0.5Gd (wt.%) alloy to unveil the dominant dyn...

Mg-2Al-1.2Ca-0.2Mn (at%)-based alloys with Ce-rich mischmetal (MM) substitution of 0–0.6 at% for Ca were hot extruded at 400 °C. The effect of MM substitution on the microstructure and mechanical properties of the extruded alloys was investigated. The as-cast Mg-2Al-1.2Ca-0.2Mn alloy is mainly composed of α-Mg, Mg2Ca and (Mg,Al)2Ca phases and Al8Mn...

A strong and ductile Mg-8Al-1Zn-1Ca-0.3Mn (wt%) alloy sheet has been successfully developed via commercial rolling process. The ultimate tensile strength, 0.2% proof stress, and elongation to failure along the rolling direction of the sheet are 371 MPa, 275 MPa, and 17.1%, respectively. The high strength and ductility are attributed to the fine rec...

Ductile aluminum matrix composites reinforced by Al18B4O33 whisker (ABO) with band-like distribution (Band-like Aluminum Matrix Composites, BAMCs) were fabricated by powder metallurgy and extrusion followed by annealing. The cracks tend to nucleate in the ABO-rich bands, but the band-like structure induces compressive residual stress then suppresse...

Commercial Mg extrusions usually develop various types of basal textures, affecting the formability and mechanical properties. The mechanisms for the formation of basal texture variations were systematically investigated for the first time based on the twinning and dynamic recrystallization (DRX) during extrusion using electron back-scatter diffrac...

Layered Ti-Al metal composite (LMC) was designed and fabricated by hot-rolling and annealing of pure Ti and Al sheets. The as-prepared composite exhibits high tensile ductility, being superior to any individual Ti or Al sheets. The stress/strain evolution and fracture behavior of the LMC were analyzed by in-situ observations during the tensile defo...

The influence of the nanosized rare earth (RE) containing precipitates on grain refinement during severe plastic deformation is investigated in detail through a study of high pressure torsion (HPT) processing of a solution treated and aged Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt%). In the early stages of HPT deformation, dislocation generation and pile-up is...

In this study, the ageing behaviour of a nanostructured Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt.%) alloy produced by solution treatment followed by high pressure torsion (HPT) was systematically investigated using hardness testing, high resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), elemental mapping, X-ray d...

An ultra-strong and ductile Mg-8.2Gd-3.8Y-1Zn-0.4Zr (wt pct) alloy was developed by using hot extrusion to modify the microstructure via forced-air cooling and an artificial aging treatment. A superior strength–ductility balance was obtained that had a tensile yield strength of 466 MPa and an elongation to failure of 14.5 pct. The local strain evol...

The microstructure evolution and mechanical properties of as-extruded Mg-11.5Gd-4.5Y-0.3Zr (wt%) alloy with Zn and Nd additions were investigated. The addition of Zn inhibits the dynamic recrystallization (DRX) due to the presence of the long-period stacking ordered (LPSO) phase. The addition of Nd promotes the precipitation of the Mg5RE (RE: rare...

Mg-10Zn-6Y-0.5Zr (wt%) alloy and Mg-10Zn-3Y-3Gd-0.5Zr (wt%) alloy with medium RE content have been fabricated by conventional casting and indirect extrusion. The as-extruded Mg-10Zn-6Y-0.5Zr (wt%) alloy shows a bimodal microstructure containing dynamic recrystallized (DRXed) grains with average grain size of 2 μm and deformed regions. In addition t...

A high strength Mg-5.1Zn-3.2Y-0.4Zr-0.4Ca (wt%) alloy containing W phase (Mg3Y2Zn3) prepared by permanent mold direct-chill casting is indirectly extruded at 350 °C and 400 °C, respectively. The extruded alloys show bimodal grain structure consisting of fine dynamic recrystallized (DRXed) grains and unrecrystallized coarse regions containing fine W...

The chemical composition of a Mg-1.1Al-0.33Ca-0.44Mn (wt%) alloy, AXM10304, has been optimized for high speed extrusion. The extrudability is substantially improved from 24 m/min to 60 m/min by slightly reducing the Ca content from 0.33 wt% to 0.24 wt%. Then, the effect of Mn content on the mechanical properties and microstructures of extruded Mg-1...

In this study, a solution-treated Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr (wt%) alloy was processed by high pressure torsion (HPT) at room temperature, with the aim of producing a material with exceptional mechanical properties. Transmission electron microscopy and X-ray diffraction line broadening analysis reveal that a nanostructured supersaturated solid solut...

An as-extruded Mg-11.5Gd-4.5Y-1.5Zn-0.4Zr (wt %) alloy with an excellent strength-ductility balance has been successfully developed by pre-annealing and hot extrusion. The effects of pre-annealing on microstructure and mechanical properties have been studied. Results show that the Mg5RE (RE: rare earth) particles, which are generated by pre-anneali...

Compared with the sole Ca or Ce/La element, the Ca-Ce/La synergistic microalloying represents an excellent strengthening effect in extruded Mg–Zn alloy, which is mainly attributed to the grain refinement during the extrusion process. Ca-Ce/La addition results in the refinement of the secondary phases and precipitates, promoting the pinning effect f...

A high strength Mg-11.7Gd-4.9Y-0.3Zr (wt %) alloy with a weak tension-compression yield asymmetry has been successfully developed by pre-deformation annealing, hot extrusion and ageing. The effects of pre-deformation annealing on the microstructure evolution and mechanical properties are studied. The results reveal that pre-deformation annealing ge...

Only trace Ca addition to the Mg–2Gd–0.5Zn–0.2Zr (at.%) alloy leads to the precipitation of Guinier-Preston (GP) zones and remarkably improves the creep resistance at elevated temperatures. The Mg–2Gd–0.5Zn–0.4Ca–0.2Zr alloy exhibits a minimumcreep rate of 5.75× 10−8 s−1 tested at 250 °C and 110MPa, its superior creep resistance is attributed to th...

The novel Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy with high content of rare earth elements has been processed successfully by high pressure torsion (HPT) starting from an as-cast condition. HPT processing was conducted at room temperature for a range of turns from 1/8 to 16, and the evolutions of microstructure and microhardness were investigated. The aver...

We have developed a wrought magnesium alloy, Mg-1.3Al-0.3Ca-0.4Mn (wt.%) or AXM10304, that can be extruded at a very high die-exist speed of 24 m/min, comparable to the extrusion speed for aluminum alloys, and that exhibits an excellent combination of strength and elongation after an age-hardening, i.e., a tensile 0.2 % proof stress of 287 MPa and...

The effect of long period stacking ordered (LPSO) phase and γ′ precipitates on the ageing behavior and mechanical properties of the extruded Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt.%) alloy was investigated. The results show that more β′ phases precipitate during ageing treatment in the LPSO phase containing alloy so that the LPSO phase containing alloy exhi...

Mg-1.58Zn-0.52Gd (wt%) alloy was indirectly extruded at different temperatures and the resulting microstructure , texture and mechanical properties were investigated. The alloy extruded at 350 °C exhibited a typical bimodal microstructure, consisting of fine dynamically recrystallized (DRXed) grains of ~3.1 μm and coarse unDRXed grains elongated al...

We investigated the effect of Al content on tensile property and microstructure of Mg–(0.6, 1.1, 1.6)Al–Ca–Mn (wt.%) alloys extruded at an extraordinary high die-exit speed of 60 m/min. All the extruded alloys showed fine grain structure with strong alignment of (0001) planes parallel to the extrusion direction. Especially, the sample containing 1....

A series of Mg–Zn–Gd alloys were developed for large strain hot rolling , cold rolling and high-speed extrusion . The hot rolled Mg–2.0Zn–0.3Gd (wt%) alloys can be successfully rolled at 300 °C for a single pass reduction of 80% without any edge cracks, and the rolled sheet exhibited high yield strength of ~210 MPa and moderate elongation of ~22% d...

Magnesium alloys containing heavy rare earth metals (HRE) have been attracting wide attention due to their remarkable age-hardening response. Extrusion of Mg-HRE alloys generally requires high ram force, leading to heat generation during the extrusion. In this study, by simply utilizing forced air cooling, high strength Mg–8.2Gd–3.8Y–1Zn–0.4Zr (wt%...

High performance Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy with high strength and excellent ductility has been successfully developed by hot extrusion. The effect of plate-shaped long period stacking ordered (LPSO) phases and solute-segregated stacking faults (SFs) on the dynamically recrystallization (DRX) behavior was analyzed. The plate-shaped LPSO phases...

As-cast Mg-7.5Gd-2.5Y-3.5Zn-0.9Ca-0.4Zr (wt%) alloy was indirectly extruded using different parameters. The microstructure, texture and mechanical properties of the as-extruded alloys were investigated. Hot extrusion effectively refines the microstructure and fragments the coarse phases in the as-cast alloy. The alloys extruded at 400 °C exhibit bi...

The effect of Ca/Al ratio on microstructure and mechanical properties of the as-cast and as-extruded Mg-Al-Ca-Mn alloys were investigated. The as-cast Mg-Al-Ca-Mn alloys with Ca/Al mass ratios less than 0.50 contain divorced and lamellar eutectic (Mg,Al)2Ca. When Ca/Al ratio is greater than 0.90, fine lamellar Mg2Ca phase is formed in the as-cast M...

Hot deformation behavior of the homogenized and quenched Mg-9Gd-2.9Y-1.9Zn-0.4Zr-0.2Ca (wt%) alloy was investigated by compression test at temperatures of 300– 500 °C and strain rates of 0.001–10 s− 1. The flow stress is sensitive to the deformation temperature and strain rate, which increases with increasing strain rate and decreasing temperature....