JournalTOCs

Acta Metallurgica Sinica (English Letters)
Journal Prestige (SJR): 0.576

Citation Impact (citeScore): 2
Number of Followers: 7

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1006-7191 - ISSN (Online) 2194-1289
Published by Springer-Verlag

[2352 journals]

Fabrication of Al-Coated Mg–Li Alloy Sheet and Investigation of Its
Properties
- Authors: Tian-Long Zhang; Toko Tokunaga; Munekazu Ohno; Mi-Lin Zhang; Kiyotaka Matsuura
  Pages: 169 - 177
  Abstract: An Al-coated Mg-8 mass% Li alloy rectangular bar was fabricated by hot extrusion, and then, it was hot-rolled into a thin sheet. The Al coating was uniform in thickness and had good bonding with the substrate during all the processing. This Al-coated Mg–Li alloy exhibited a good corrosion resistance in a 0.5 mass% HCl aqueous solution. No intermetallic compound was observed at the Al/Mg–Li interface after the extrusion and the rolling. The Al-coated Mg–Li alloy sheet exhibited an elongation to fracture of 35% at room temperature at a strain rate of 0.001 s−1 without any debonding between the coating and the substrate. When tensile tested at 573 K at 0.001 s−1 in the air, the Al coating remained undamaged even until an elongation of about 150%. Further elongation generated cracks on the coating and the specimen fractured at an elongation of about 200%. In an Ar atmosphere, the specimen exhibited a fracture elongation of over 400% under the same conditions at 573 K at 0.001 s−1, although a large number of cracks generated on the Al coating.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0774-9
  Issue No: Vol. 32, No. 2 (2019)
Detailed Structures and Formation Mechanisms of Well-Known Al 10 RE 2 Mn 7
Phase in Die-Cast Mg–4Al–4RE–0.3Mn Alloy
- Authors: Qiang Yang; Shu-Hui Lv; Fan-Zhi Meng; Kai Guan; Bai-Shun Li; Xu-Hu Zhang; Jing-Qi Zhang; Xiao-Juan Liu; Jian Meng
  Pages: 178 - 186
  Abstract: The detailed structures and the corresponding formation mechanisms of the well-known Al10RE2Mn7 phase in the conventional die-cast Mg–4Al–4RE–0.3Mn alloy were thoroughly investigated using transmission electron microscopy (TEM). The results indicate that the Al10RE2Mn7 phase ordinarily contains both normal \((11\overline{2} 1)\) twins and orientation twins. Both detailed TEM observations and density functional theory calculations indicate that the Al10RE2Mn7 phase is transferred from the Al8REMn4 phase following an orientation relationship as \([010]_{{{\text{Al}}_{ 8} {\text{REMn}}_{ 4} }} / /[\overline{1} 101]_{{{\text{Al}}_{ 1 0} {\text{RE}}_{ 2} {\text{Mn}}_{ 7} }}\) and \((101)_{{{\text{Al}}_{ 8} {\text{REMn}}_{ 4} }} / /(11\overline{2} 0)_{{{\text{Al}}_{ 1 0} {\text{RE}}_{ 2} {\text{Mn}}_{ 7} }}\) . Moreover, forming orientation twins in the Al10RE2Mn7 phase is attributed to the blurry regions at incoherent twin boundaries in the Al8REMn4 phase. Finally, these formed orientation twins result in the \((11\overline{2} 1)\) twins in the Al10RE2Mn7 phase.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0819-0
  Issue No: Vol. 32, No. 2 (2019)
Solute Clusters/Enrichment at the Early Stage of Ageing in Mg–Zn–Gd
Alloys Studied by Atom Probe Tomography
- Authors: Xin-Fu Gu; Tadashi Furuhara; Leng Chen; Ping Yang
  Pages: 187 - 193
  Abstract: Three-dimensional distribution of solute elements in an Mg–Zn–Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe (3DAP) tomography. Based on the radius distribution function, it is found that Zn–Gd solute pairs in Mg matrix appear mainly at two peaks at early stage of ageing, and the separation distance between Zn and Gd atoms could be well rationalized by the first-principle calculation. Moreover, the fraction of Zn–Gd solute pairs increases first and then decreases due to the precipitation of long-period stacking ordered (LPSO) structures. Both the composition of the structural unit in LPSO structure and the solute enrichment around it are quantified. It is found that Zn and Gd elements are synchronized in the LPSO structure, and solute segregation of pure Zn or Gd is not observed at the transformation front of the LPSO structure in this alloy. In addition, the crystallography of transformation front is further determined by 3DAP data.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0840-3
  Issue No: Vol. 32, No. 2 (2019)
Influence of Voltage on the Corrosion and Wear Resistance of Micro-Arc
Oxidation Coating on Mg–8Li–2Ca Alloy
- Authors: Bing-Yu Qian; Wei Miao; Min Qiu; Fan Gao; Dong-Hui Hu; Jian-Feng Sun; Rui-Zhi Wu; Boris Krit; Sergey Betsofen
  Pages: 194 - 204
  Abstract: Calcium phosphate (CaP) coatings were prepared on Mg–8Li–2Ca magnesium alloy by micro-arc oxidation (MAO) in an alkaline Na3PO4–Ca[C3H7O6P] base solution at the different applied voltages. Scanning electron microscope and X-ray diffraction were employed to characterize the microstructure and phase composition of the coatings, respectively. The corrosion resistance of the coatings was assessed by potential dynamic polarization curves, electrochemical impedance spectroscopy and hydrogen evolution experiment in simulated body fluids solution. The friction and wear properties were evaluated by friction and wear testing machine. The results demonstrate that the coating surface is porous and mainly composed of MgO, Ca5(PO4)3(OH) and CaH2P2O5. With the increase in voltage, the corrosion resistance and wear resistance of the MAO coating are both enhanced. The corrosion current density of the MAO coating decreases about two orders of the magnitude compared to the substrate. Additionally, wear and corrosion mechanisms are discussed.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0845-y
  Issue No: Vol. 32, No. 2 (2019)
Effect of Partially Substituting Ca with Mischmetal on the Microstructure
and Mechanical Properties of Extruded Mg–Al–Ca–Mn-Based Alloys
- Authors: Chao Xu; Taiki Nakata; Guo-Hua Fan; Kosuke Yamanaka; Guang-Ze Tang; Lin Geng; Shigeharu Kamado
  Pages: 205 - 217
  Abstract: 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 Al8Mn5 precipitates, whereas the substitution of MM brings about the formation of Al11MM3, Al2MM phases and Al10MM2Mn7 particles with the absence of (Mg,Al)2Ca phase. The volume fraction of MM-containing phases increases with increasing MM contents. All of the extruded alloys exhibit bimodal microstructure comprising fine dynamically recrystallized grains with almost random orientation and coarse deformed grains with strong basal texture. Dense nanosized planar Al2Ca and spherical Al–Mn phases precipitate inside the deformed grains. High tensile yield strengths of ~ 350 MPa and moderate elongations to failure of > 12% are obtained in all extruded alloys; the MM substitution induces negligible difference in the tensile properties at ambient temperature, while the highest MM substitution improves the strength at 180 °C due to the better thermal stability of the fragmented MM-containing phases.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0820-7
  Issue No: Vol. 32, No. 2 (2019)
Corrosion Resistance of AZ91 Mg Alloy Modified by High-Current Pulsed
Electron Beam
- Authors: Peng-Peng Wu; Kun-Kun Deng; Kai-Bo Nie; Zhong-Zhong Zhang
  Pages: 218 - 226
  Abstract: The high-current pulsed electron beam (HCPEB) treatment with current density 6 J/cm2 was applied on AZ91 Mg alloy to improve its corrosion resistance. Results showed that the net-like Mg17Al12 disappeared on the surface of AZ91 Mg alloy after irradiation by HCPEB, which was instead of supersaturated Al element on the surface. Nevertheless, the application of HCPEB also led to the formation of crater-like and groove-like structures as well as micro-cracks on the surface of AZ91 Mg alloy. After HCPEB treatment by 3, 5 and 10 pulses, the AZ91 Mg alloy exhibited better corrosion resistance. However, the increasing amount of micro-cracks reduced the anti-corrosive properties of AZ91 Mg alloy as the pulse increased to 20 and 30.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0798-1
  Issue No: Vol. 32, No. 2 (2019)
Influence of Annealing Treatments on Microstructure and Mechanical
Properties of an Extruded Mg AZ31/Al 7050 Laminate
- Authors: Yang Wu; Yun-Chang Xin; Xiang-Sheng Xia; Bo Feng; Yan-Bin Wang; Zu-De Zhao
  Pages: 227 - 234
  Abstract: Mg AZ31/Al 7050 laminate was fabricated by co-extrusion directly from the as-cast Mg AZ31 and Al 7050 billets. The influence of annealing temperature and annealing time on microstructure and mechanical behavior of the extruded Mg/Al laminate was systematically studied. Results show that annealing treatments at 250 °C for 3 h or at 350 °C for 3 h do not result in an obvious grain coarsening of Mg layer and cannot remove the heterogeneous structure. Annealing does not vary texture in the Mg layer, a large fraction of <0002>//ND and a small fraction of <0002>//TD, but the intensity of component <0002>//ND weakens to some extent. Lamellar microstructure in the Al layer remains after annealing at 250 °C for 3 h or at 350 °C for 3 h. High fractions of the texture components S and cube exist in the extruded sample, and annealing treatment hardly changes their fractions. Post-annealing treatment will largely reduce yield strength of extruded plate and increase plasticity slightly. The yield strength drops from 302 MPa to 206 MPa after annealing at 250 °C for 3 h and to 141 MPa after annealing at 350 °C for 3 h. The elongation to fracture increases from 1.5% to 5.4% after annealing at 250 °C for 3 h and to 4.8% at 350 °C for 3 h. The corresponding mechanism was discussed.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0802-9
  Issue No: Vol. 32, No. 2 (2019)
Microstructure and Mechanical Properties of AZ31 Mg Alloy Fabricated by
Pre-compression and Frustum Shearing Extrusion
- Authors: Kun Sheng; Li-Wei Lu; Yao Xiang; Min Ma; Zhong-Chang Wang
  Pages: 235 - 244
  Abstract: The AZ31 Mg alloys were processed by 6% pre-compression and frustum shearing extrusion at various temperatures, and the microstructure, texture and mechanical properties of the resulting alloys are systematically investigated. The results show that the grain size monotonically increases from 6.4 to 12.6 μm and the texture intensity increases from 6.7 to 9.6 with the increase in the extrusion temperature. The combining effect of the pre-twinning and the frustum shearing deformation is found to contribute to the development of the weak basal texture in Mg alloys. The Mg alloy sheet produced at the extrusion temperature of 563 K exhibits excellent mechanical properties. The yield strength, ultimate tensile strength and elongation for the extruded alloys are 189.6 MPa, 288.4 MPa and 24.9%, respectively. Such improved mechanical properties are comparable or even superior to those of the alloys subjected to other deformation techniques, rendering the pre-compression and frustum shearing extrusion a promising way for further tailoring properties of Mg alloys.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0843-0
  Issue No: Vol. 32, No. 2 (2019)
Microstructure Evolution of Extruded Mg–6Gd Alloy Under
175 °C and 150 MPa
- Authors: Rong-Guang Li; Farhan Asghar; Jing-Huai Zhang; Guang-Yan Fu; Qun Liu; Bei-Tao Guo; Yong-Mei Yu; Shu-Guo Guo; Yong Su; Xue-Jiao Chen; Lin Zong
  Pages: 245 - 252
  Abstract: The tensile creep behavior of extruded Mg–6Gd alloy, having the tensile yield strength of ~ 110 MPa at 175 °C, has been investigated under 175 °C and 150 MPa. In this study, the extruded Mg–6Gd sample exhibits the total tensile strain of ~ 10.5% after the creep time of 1100 h, and the fast plastic strain of ~ 4.6% at the beginning of the creep test. The microstructure result suggests that the dislocation deformation is the main deformation mode during creep, and the grains with orientation close to 〈0001〉 ED disappear after creep. The creep process containing a low creep strain has no effective promotion for the precipitation compared with the aging process without strain. The origination of creep crack is related to the formation of precipitate-free zone during creep. The work offers an important implication to research the microstructure evolution under an applied stress in a weak aging response Mg alloy.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0817-2
  Issue No: Vol. 32, No. 2 (2019)
Influence of Extrusion Speed on the Microstructure Evolution, Interface
Bonding and Mechanical Response of Mg MB26/Al 7075 Composite Rod
- Authors: Yu Chen; Rui Zhang; Tao Zhou; Li Hu; Jian Tu; Lai-Xin Shi; Yan Zhi; Li-Wei Lu; Qiang Chen; Ben-Hong Liao; Lei Liu; Wen-Jun Ge; Jing Xiao; Ming-Bo Yang
  Pages: 253 - 262
  Abstract: The Mg MB26/Al 7075 composite rod, in which Mg MB26 serves as the sleeve and Al 7075 serves as the core, is fabricated via the process of co-extrusion. The influence of extrusion speed on the microstructure evolution, interface bonding and mechanical response of the Mg MB26/Al 7075 composite rod is investigated. The results show that the typical extrusion texture of Mg sleeve does not change during co-extrusion; however, the average grain size in the Mg sleeve slightly changes from 1.57 μm in the case of extrusion speed of 0.3 mm/s to 2.78 μm in the case of extrusion speed of 2.1 mm/s. The thickness of interface transition layer increases significantly from 5.5 to 50 μm, and therefore, the interface bonding becomes deteriorative with increasing extrusion speed; in particular, many cavities emerge in the case of 1.2 and 2.1 mm/s.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0838-x
  Issue No: Vol. 32, No. 2 (2019)
In Situ Electron Backscatter Diffraction Analysis for Microstructure
- Authors: Fang-Wei Jiao; Li Jin; Jie Dong; Feng-Hua Wang
  Pages: 263 - 268
  Abstract: Previous studies showed that significant increases in elongation in Mg–Ce alloys due to the Ce addition and the solute drag effect by Ce addition were ascribed to the non-basal dislocation slip activating and the texture altering. The microstructure evolution and deformation models of extruded Mg-0.5 wt%Ce alloy rods under uniaxial tension have been studied using in situ electron backscatter diffraction. The basal and non-basal slips were characterized by using slip line trace analysis. The results provide evidence for that pyramidal slip activated during deformation, besides basal slip and extension twinning, which contributes to the texture weakening and ductility increasing in Mg-0.5 wt%Ce alloy.
  PubDate: 2019-02-01
  DOI: 10.1007/s40195-018-0865-7
  Issue No: Vol. 32, No. 2 (2019)
Effect of Mo Addition on Corrosion Behavior of High-Entropy Alloys
CoCrFeNiMo x in Aqueous Environments
- Authors: Xu-Liang Shang; Zhi-Jun Wang; Qing-Feng Wu; Jin-Cheng Wang; Jun-Jie Li; Jia-Kang Yu
  Pages: 41 - 51
  Abstract: The corrosion behavior of CoCrFeNiMox alloys was investigated in aqueous environments, NaCl and H2SO4 solutions, respectively, to simulate typical neutral and acidic conditions. The cyclic polarization curves in NaCl and the potentiodynamic curves in H2SO4 clearly reveal the beneficial effects of Mo and the detrimental effect of σ-phase on the corrosion resistance. The X-ray photoelectron spectroscopy results of CoCrFeNiMox alloys in H2SO4 solution indicate that Cr and Mo predominate the corroded surface of the alloys, where Mo primarily exists in the form of MoO3.
  PubDate: 2019-01-01
  DOI: 10.1007/s40195-018-0812-7
  Issue No: Vol. 32, No. 1 (2019)
Microstructural Characteristics and Mechanical Properties of Low-Alloy,
Medium-Carbon Steels After Multiple Tempering
- Authors: Erfan Abbasi; Quanshun Luo; Dave Owens
  Pages: 74 - 88
  Abstract: The microstructure and mechanical properties of NiCrMoV- and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature, regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels.
  PubDate: 2019-01-01
  DOI: 10.1007/s40195-018-0805-6
  Issue No: Vol. 32, No. 1 (2019)
Elastic Properties and Stacking Fault Energies of Borides, Carbides and
Nitrides from First-Principles Calculations
- Authors: Yong Zhang; Zi-Ran Liu; Ding-Wang Yuan; Qin Shao; Jiang-Hua Chen; Cui-Lan Wu; Zao-Li Zhang
  Abstract: Owing to the excellent elastic properties and chemical stability, binary metal or light element borides, carbides and nitrides have been extensively applied as hard and low-compressible materials. Researchers are searching for harder materials all the time. Recently, the successful fabrication of nano-twinned cubic BN (Tian et al. Nature 493:385–388, 2013) and diamond (Huang et al. Nature 510:250–253, 2014) exhibiting superior properties than their twin-free counterparts allows an efficient way to be harder. From this point of view, the borides, carbides and nitrides may be stronger by introducing twins, whose formation tendency can be measured using stacking fault energies (SFEs). The lower the SFEs, the easier the formation of twins. In the present study, by means of first-principles calculations, we first calculated the fundamental elastic constants of forty-two borides, seventeen carbides and thirty-one nitrides, and their moduli, elastic anisotropy factors and bonding characters were accordingly derived. Then, the SFEs of the {111} < 112 > glide system of twenty-seven compounds with the space group F \(\bar{4}\) 3m or Fm \(\bar{3}\) m were calculated. Based on the obtained elastic properties and SFEs, we find that (1) light element compounds usually exhibit superior elastic properties over the metal borides, carbides or nitrides; (2) the 5d transition-metal compounds (ReB2, WB, OsC, RuC, WC, OsN2, TaN and WN) possess comparable bulk modulus (B) with that of cBN (B = 363 GPa); (3) twins may form in ZrB, HfN, PtN, VN and ZrN, since their SFEs are lower or slightly higher than that of diamond (SFE = 277 mJ/m2). Our work can be used as a valuable database to compare these compounds.
  PubDate: 2019-02-04
  DOI: 10.1007/s40195-019-00873-8
Recent Research on the Deformation Behavior of Particle Reinforced
Magnesium Matrix Composite: A Review
- Authors: Kun-Kun Deng; Cui-Ju Wang; Kai-Bo Nie; Xiao-Jun Wang
  Abstract: Particle reinforced magnesium matrix composite (PMMC) possesses the merits of high specific strength, high specific modulus, better dimensional stability, good wear resistance and lower production cost, which is thought as a promising material in the field of aerospace, automobile, electronic communication, etc. To eliminate the casting defect, the PMMC is usually experienced hot deformation process. The present paper mainly focuses on the deformation behavior of PMMCs. First, the development of PMMCs based on particle size is introduced. Then, the hot deformation technology and deformation mechanism of PMMCs at elevated temperature are given and analyzed, respectively. After reviewing the dynamic recrystallization and texture of PMMCs, its future development is suggested based on the current research progress.
  PubDate: 2019-02-04
  DOI: 10.1007/s40195-019-00872-9
Effect of Acidified Aerosols on Initial Corrosion Behavior of Q235 Carbon
Steel
- Authors: Miao-Ran Liu; Xiao Lu; Qi Yin; Chen Pan; Chuan Wang; Zhen-Yao Wang
  Abstract: The effect of simulated acidified marine aerosols on the corrosion morphology of carbon steel was studied using an in situ optical stereomicroscope and scanning electron microscope equipped with an energy-dispersive spectrometer and a white-light interferometer. The morphologies of the carbon steel were identified under marine aerosols with different droplet diameters, pH, and acidifications. The results showed that corrosion was initiated in tens of seconds under aerosol droplets acidified by HCl or H2SO4. Despite the differences in the acidifier and diameter, corrosion for acidified droplets with pH > 2 was general corrosion. For acidified droplets with pH < 1, the corrosion morphology depended on the acidifier species, the ring-like morphology for HCl and ridge-like morphology for H2SO4. The segregation of Cl− was believed to be the main factor for the formation of the corrosion morphology under acidified droplets with pH < 1. Also, the concentration of SO42− in the droplets had some effect on the segregation of Cl− ions when pH < 1.
  PubDate: 2019-01-30
  DOI: 10.1007/s40195-018-0853-y
Recent Progress and Development in Extrusion of Rare Earth Free Mg Alloys:
A Review
- Authors: Shuai-Ju Meng; Hui Yu; Shao-Da Fan; Qi-Zhi Li; Sung Hyuk Park; Joung Sik Suh; Young Min Kim; Xiao-Long Nan; Ming-Zhe Bian; Fu-Xing Yin; Wei-Min Zhao; Bong Sun You; Kwang Seon Shin
  Abstract: Mg and its alloys are the lightest structural metals available and are extremely attractive for applications as lightweight components, particularly in the automobile, electronic, and aerospace industries. The global market for wrought Mg alloys has steadily expanded over the past decade. And numerous studies have been carried out to meet this increasing demand of high-performance Mg alloys. However, Mg extrusion alloys have had a very limited usage so far. To overcome existing industrial challenges, one desirable approach is the development of low-cost rare earth (RE) free Mg extrusion alloys with superior mechanical properties. This review will introduce the recent research highlights in the extrusion of Mg alloys, specifically focusing on low-cost RE-free Mg alloy. The results from both the literature and our previous study are summarized and critically reviewed. Several aspects of RE-free Mg extrusion alloys are described in detail: (1) novel alloying designs including Mg–Al-, Mg–Zn-, Mg–Ca-, Mg–Sn-, and Mg–Bi-based alloys, (2) advanced extrusion techniques, and (3) extrusion-related severe plastic deformation (SPD) processing. Accordingly, considering the large gap in mechanical properties between the current RE-free Mg alloys and high-performance aluminum alloys, new alloy design, processing route control, and recommendations for future research on RE-free Mg extrusion alloys are also proposed. We hope this review will not only offer insightful information regarding the extrusion of RE-free Mg alloys but also inspire the development of new Mg extrusion technologies.
  PubDate: 2019-01-17
  DOI: 10.1007/s40195-018-00871-2
Effect of Cooling Rates in Coiling Process on Microstructures and
Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel
- Authors: Xiao-Hui Wang; Jian Kang; Yun-Jie Li; Guo Yuan; R. D. K. Misra; Guo-Dong Wang
  Abstract: In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation-induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9–11% at cooling rates of 0.05–1 °C/s and 4–6% at cooling rates of 5–10 °C/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05 °C/s and 0.5 °C/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 °C/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5 °C/s remained stable.
  PubDate: 2019-01-10
  DOI: 10.1007/s40195-018-00868-x
Microstructural Evolution, Mechanical Properties and Thermal Stability of
Gradient Structured Pure Nickel
- Authors: Xiao Li; Bo Guan; Yun-Fei Jia; Yun-Chang Xin; Cheng-Cheng Zhang; Xian-Cheng Zhang; Shan-Tung Tu
  Abstract: The microstructural evolution of pure nickel treated by deep rolling (DR) technique with different indent depths was investigated by means of optical microscopy and transmission electron microscopy. The surface roughness, hardness and residual stress distribution along the depth from surface were measured. Moreover, the DR-treated sample was annealed at temperatures from 300 to 700 °C for 2 h. The results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR process. With increasing indent depth of the DR, the gradient microhardness on the cross section of sample significantly increases, the maximum compressive residual stress decreases, and the affecting region of residual stress increases. The results of thermal stability depict that the microstructure can be stable as temperature up to 300 °C, and the abnormal grain growth and annealing twins are observed at 600 °C.
  PubDate: 2019-01-10
  DOI: 10.1007/s40195-018-00870-3
Effects of Post-weld Heat Treatment on Microstructure, Mechanical
Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy
TIG-Welded Joints
- Authors: Deng-Kui Zhang; Guo-Qing Wang; Ai-Ping Wu; Ji-Guo Shan; Yue Zhao; Tian-Yi Zhao; Dan-Yang Meng; Jian-Ling Song; Zhong-Ping Zhang
  Abstract: In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows different microstructure and microhardness due to the different welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing effect on the weld and their existence was more of an adverse effect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.
  PubDate: 2019-01-08
  DOI: 10.1007/s40195-018-00869-w