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Si-Assisted solidification path and Microstructure Control of 7075 Aluminum Alloy with Improved Mechanical Properties by Selective Laser Melting

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Acta Metallurgica Sinica(English Letters) 2022年第9期35卷 1424-1438页

作者： Junwei Sha Meixian Li Lizhuang Yang Xudong Rong Bowen Pu Dongdong Zhao Simi Sui Xiang Zhang Chunnian He Jianglin Lan Naiqin Zhao School of Materials Science and Engineering and Tianjin Key Laboratory of Composites and Functional Materials Tianjin UniversityTianjin300350China Collaborative Innovation Center of Chemical Science and Engineering Tianjin300350China Key Laboratory of Advanced Ceramics and Machining Technology Ministry of EducationTianjin300350China Central Iron and Steel Research Institute(CISRI) Beijing100081China

The construction and application of traditional high-strength 7075 aluminum alloy(Al7075) through selective laser melting(SLM) are currently restricted by the serious hot cracking phenomenon. To address this critical issue, in this study, Si is employed to assist the SLM printing of high-strength Al7075. The laser energy density during SLM is optimized, and the eff ects of Si element on solidification path, relative density, microstructure and mechanical properties of Al7075 alloy are studied systematically. With the modified solidification path, laser energy density, and the dense microstructure with refined grain size and semi-continuous precipitates network at grain boundaries, which consists of fine Si, β-MgSi, Q-phase and θ-AlCu, the hot cracking phenomenon and mechanical properties are eff ectively improved. As a result, the tensile strength of the SLM-processed Si-modified Al7075 can reach 486 ± 3 MPa, with a high relative density of ~ 99.4%, a yield strength of 291 ± 8 MPa, fracture elongation of(6.4 ± 0.4)% and hardness of 162 ± 2(HV) at the laser energy density of 112.5 J/mm~3. The main strengthening mechanism with Si modification is demonstrated to be the synergetic enhancement of grain refinement, solution strengthening, load transfer, and dislocation strengthening. This work will inspire more new design of high-strength alloys through SLM.

关键词： Selective laser melting(SLM) 7075 aluminum alloy High-strength alloy Microstructure control solidification path

Relationship between solidification path,microstructure evolution and solidification cracking behavior of Mg-Al-Ca alloy during TIG welding

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Journal of Materials Science & Technology 2024年第15期182卷 176-186页

作者： Sensen Chai Qingwei Dai Shiyu Zhong Qingshan Yang Limeng Yin Dingfei Zhang Jingkai Feng Qian Li School of Metallurgy and Materials Engineering Chongqing University of Science and TechnologyChongqing 401331China College of Materials Science and Engineering Chongqing UniversityChongqing 400045China Department of Mechanical Engineering City University of Hong KongHong Kong 999077SARChina XI’AN Rare Metal Materials Institute Co. Ltd.Xi’an 710016China State Key Laboratory of Advanced Special Steels&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering Shanghai UniversityShanghai 200444China National Engineering Research Center for Magnesium Alloy Chongqing UniversityChongqing 400044China National Key Laboratory of Advanced Casting Technologies Chongqing UniversityChongqing 400044Chi

The high-strength and creep-resistant Mg-Al-Ca-Mn alloys have broad application ***,solidification cracking occurs in these alloys in certain conditions and the origin is still *** work investigated the relationship between the solidification path,microstructure evolution and solidification cracking behavior of the Mg-xAl-2Ca-Mn alloys during tungsten inert gas(TIG)*** show that when the fusion zone’s Ca/Al mass ratio ranges from 0.4 to 1.64,solidification cracking occurs at a Ca/Al mass ratio of∼*** the Ca/Al mass ratio approaches this value,the grain size increases,and the Laves phases are reduced *** early formed Laves phases play an important role in promoting dendrite segmentation,refining grain size and enhancing grain *** a solidification path delays the formation of Laves phases,the Laves phases will be reduced accompanied by grain *** such a solidifying microstructure,intergranular cavitation is easy to occur,and the resistance of the semi-solid alloy to crack propagation is severely reduced.

关键词： Magnesium alloy Welding solidification cracking solidification path Laves phase

Influence of Al addition on solidification path and hot tearing susceptibility of Mg-2Zn-(3+0.5 x)Y-x Al alloys

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Journal of Magnesium and Alloys 2019年第2期7卷 272-282页

作者： Guojia Zhang Yue Wang Zheng Liu Shimeng Liu School of Materials Science and Engineering Shenyang University of technologyShenyang 110870P.R.China

Hot tearing susceptibility(HTS)of Mg-2Zn-(3+0.5 x)Y-x Al(x=0,2 and 3 at%)alloys is predicted by using modified Clyne-Davies’model(CSC^(∗)).The solidification path,solidification characteristic temperatures and dendritic coherency solid fraction have been studied by double-thermocouple thermal *** solidification contraction stress ***(and time)curves are measured by using a“T”type hot tearing *** results reveal that the CSC^(∗)prediction values are in good agreement with the experimental ***,Al_(2)Y phase acts as the heterogeneous nucleation core ofα-Mg and significantly influences the grain *** has been observed that minimum grain size,optimal dendritic coherency and minimum HTS are exhibited by Mg-2Zn-(3+0.5 x)Y-x Al alloy(x=2).Furthermore,when Al content was increased to 3 at%,Al_(2)Y phase exhibited a peritectic reaction and transformed into a mixed structure of Al_(2)Y and Al+Al_(3)Y phases,which increased the HTS of the alloy due to reduced fine-grained Al_(2)Y content.

关键词： Mg-Zn-Y-Al alloys Hot tearing susceptibility(HTS) solidification path Clyne-Davies’model(CSC^(∗)) Dendritic coherency

Microstructures,micro-segregation and solidification path of directionally solidified Ti-45Al-5Nb alloy

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China Foundry 2016年第2期13卷 107-113页

作者： Liang-shun Luo Tong Liu Kun Li Yan-qing Su Jing-jie Guo Heng-zhi Fu National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnoloryHarbin 150001China China FA W Casting Company Limited Changchun 130011China State Key Laboratory of Advanced Welding and JoiningHarbin Institute of Technolory.Harbin 150001.China

To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were *** results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^(-1) under the temperature gradients of 15-20 K·mm^(-1), and the primary phase is transformed into an α phase at relatively higher growth rates(V >20 μm·s^(-1)). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^(-1) under a temperature gradient of 15 K·mm^(-1). The increase of temperature gradient to 20 K·mm^(-1) can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L+β L+β→αα+β_R β→ααα→γα+γα→α_2+γγ_R+(α_2+γ), in which β_R and γ_R mean the residual β and

关键词： TiAl-Nb alloy directional solidification microstructure micro-segregation solidification path

As-cast microstructures and solidification paths of the Nb–Si–Ti ternary alloys in Nb_5Si_3–Ti_5Si_3region

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Rare Metals 2013年第5期32卷 502-511页

作者： Yan Li Chang-Rong Li Zhen-Min Du Cui-Ping Guo Xin-Qing Zhao School of Materials Science and Engineering University of Science and Technology Beijing School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics

Abstract The as-cast microstructures and solidification paths of the Nb-Si-Ti ternary alloys in the NbsSi3-TisSi3 region were investigated. Since there exist some isomor- phous compounds in the NbsSi3-TisSi3 region, such as aNbsSi3 with B3Cr5 prototype, 13NbsSi3 with Si3W5 pro- totype, 7NbsSi3 with MnsSi3 prototype, and TisSi3 with MnsSi3 prototype, the primary solidification areas of these compounds were not typically indentified in previous experiments. In the present paper, the microstructure observation, the phase identification, and the composition measurement were performed using scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and electron probe microanalysis （EPMA）, respectively. No ternary compound is found. There exist three primary solidification areas, 13Nbs_x（Ti）xSi3, ~Nbs_x（Ti）xSi3, and Tis-x（Nb）xSi3 in the NbsSi3-TisSi3 region. Together with the literaturereported experimental data and optimization results, the liquidus projection of the whole Nb-Si-Ti ternary system is constructed, and totally ten primary solidification areas-- diamond-Si, Nb1-x（Ti）xSi2, Ti1-x（Nb）xSi2, Ti1-x（Nb）xSi, Ti5-x（Nb）xSi4, βNb5-x（Ti）xSi3,αNb5-x（Ti）xSi3, Ti5-x （Nb）xSi3, （Nb,Ti）3Si, and BCC--and nine transitional invariant reactions-L ＋ Nb1-x（Ti）xSi2 → Ti1-x（Nb）x Si2 ＋ Si, L ＋ Nb1-x（Ti）xSi2 → Ti1-x（Nb）xSi2 ＋ Ti5- （Nb）xSi4, L ＋ Ti5-x（Nb）xSi4 → Ti1-x（Nb）xSi2 ＋ Ti1-x （Nb）xSi, L ＋ 13Nb5-x（Ti）5Si3→ Nb1-x（Ti）xSi2 ＋ Ti5-x （Nb）xSi4, L ＋ βNb5-x（Ti）xSi3→b5-x（Ti）xSi3 ＋Ti5-x （Nb）xSi4, L ＋ αNb5-x（Ti）αSi3 → Ti5-x（Nb）xSi3 ＋ Ti5-x（Nb）x Si4, L ＋ αNb5-x（Ti）xSi3 →βNb5-x（Ti）xSi3 ＋ Ti5-x（Nb）xSi3, L ＋ βNb5-xTb-xSi3 → Ti5-x（Nb）xSi3 ＋（Nb,Ti）3Si, and L ＋（Nb,Ti）3Si → Ti5-x（Nb）xSi3 ＋ BCC are confirmed.

关键词： Nb-Si-Ti ternary system Liquidus projection Microstructure solidification path

Thermo-Calc based multi-component micro-segregation model and solidification paths calculations

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China Foundry 2012年第3期9卷 269-274页

作者： Zhao Guangwei Li XinZhong Xu Daming Guo Jingjie Fu Hengzhi Du Yong He Yuehui School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083HunanChina

On the basis of a multi-length scale modeling, a mixture-averaged multi-component/multiphase micro- segregation model was proposed without pre-set function for the micro-scale solute profile. The model explains the effect of morphologies of solidifying phases and solid back diffusion （SBD） on segregation, and covers the two limiting solidification cases of Scheil and Lever-rule models. A commercial Thermo-Calc software package/database was linked to the algorithms via its TQ6-interface for instantaneous determination of the related thermodynamic data of the multi-component alloys. The influences of cooling rate and other parameters on the solidification path and micro-segregation behavior were numerically investigated by sample calculation of the ternary AI-Cu-Mg alloys. A parallel experimental investigation on AI-Cu-Si alloys solidified under different cooling conditions was conducted to validate the theoretical model. Reasonable agreements were gained between the predicted solidification paths and the measured results.

关键词： solidification path micro-segregation multi-component/multi-phase alloys thermo-Calc

Influence of Substituting W for Nb or Hf on solidification Behavior of a Typical Co-Ni-Al-W Based Superalloy

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Acta Metallurgica Sinica(English Letters) 2024年第11期37卷 1907-1920页

作者： Huifang Zhang Jun Xie Qi Li Hao Wu Jinjiang Yu Hongyu Chai Fengjiang Zhang Jinguo Li Yizhou Zhou Xiaofeng Sun Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei230026China

Understanding the effects of various elements on solidification behavior is crucial for designing the composition ofγ’-strengthened Co-based superalloys and is fundamental for controlling the as-cast structure and formulating subsequent heat treatment *** research investigated the effects of replacing 1 at.%W with 1 at.%Nb or Hf elements on the solidification behavior of Co-Ni-Al-W-based *** findings revealed that substituting W with Nb and Hf resulted in a notable decrease in both the solidus temperature(TS)and liquidus temperature(TL).Specifically,the substitution of W with Nb lowered TS from 1353℃ to 1332℃ and TL from 1383℃ to 1368℃,while replacing W with Hf decreased TS from 1353℃ to 1330℃ and TL from 1383℃ to 1366℃.Moreover,both Nb and Hf element are positive segregation element,while Nb decreases and Hf increases W segregation,*** the final solidification stage,the substitution of W with Nb resulted in the formation of eutectic(γ+γ’),Co_(3)Ta,and a small amount ofμ-Co7Nb6 phase,while replacing W with Hf resulted in the formation of the Laves phase andβ-CoAl *** solidification paths of the three alloys were confirmed based on the result of differential scanning calorimetry,isothermal solidification experiment and Thermo-calc *** results offer a theoretical basis for the composition design and optimization of heat treatment processes for Co-Ni-Al-W-based superalloys.

关键词： Co-Ni-Al-W-based superalloys solidification microstructure Segregation solidification path

Influence of zinc and silver additions on hot tearing susceptibility of Mg-14Gd-0.4Zr alloy

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Journal of Rare Earths 2024年第12期42卷 2231-2238页

作者： Lixiang Yang Shaozhu Wang Yuanding Huang Zhengquan Hou Hai Wu Xiwang Dong Hui Shi Wenbing Zou Dejiang Li Fei Li Baode Sun Zhongquan Li Norbert Hort Lv Xiao Shanghai Spaceflight Precision Machinery Research Institute Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming and State Key Lab of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiao Tong University Institute of Metallic Biomaterials Helmholtz-Zentrum Hereon School of Mechanical & Automotive Engineering Qingdao University of Technology National Engineering Research Center of Light Alloy Net Forming and State Key Lab of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiao Tong University

The effects of 1Zn and/or 2Ag additions on the hot tearing susceptibility（HTS） of Mg-14Gd-0.4Zr（wt%）alloy were studied. The HTS was evaluated by both theoretical predictions using Kou's criterion and experimental observations based on the in situ force-temperature recorded constrained rod casting（ISFTCRC） method. The results show that the order of HTS from high to low is Mg-14Gd-2Ag-1Zn-0.4Zr,Mg-14Gd-2Ag-0.4Zr, Mg-14Gd-1Zn-0.4Zr and Mg-14Gd-0.4Zr. Adding 1Zn and/or 2Ag changes the solidification path and the solidification interval, which affects the hot tearing susceptibility. Alloying elemental 1Zn slightly increases the solidification interval and the temperature range in the square root of the solid phase fraction(fs1/2) range of 0.949-0.995, resulting in a slight increase in the hot tearing susceptibility. The addition of 2Ag drastically widens both the solidification interval and the temperature range in the fs1/2range of 0.949-0.995, thus significantly increasing the hot tearing *** to the addition of 2Ag alone, the broadening degree of both the solidification interval and the temperature range in the fs1/2range of 0.949-0.995 is greater by adding the composite 2Ag/1Zn, which further promotes the occurrence of hot tearing. A narrower solidification interval and a temperature range in the fs1/2range of 0.949-0.995 result in a lower hot tearing susceptibility.

关键词： Mg-Gd-Ag/Zn Hot tearing solidification interval solidification path Differential scanning calorimetry/Thermal gravimetric (DSC/TG) rare earths

Effects of Ru content on phase transformation and compression property of cast TiAl alloys

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China Foundry 2020年第6期17卷 393-401页

作者： Jie-ren Yang Zi-xiang Jiao Dong-dong Zhu Yu-lun Wu Zi-tong Gao Rui Hu State Key Laboratory of solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment Northwestern Polytechnical UniversityXi'an 710072China School of Mechanical Engineering&Key Laboratory of Air-driven Equipment Technology of Zhejiang Province Quzhou UniversityQuzhou 324000China

Ruthenium(Ru)is a promising element to heighten the comprehensive mechanical properties of TiAl *** the present study,the phase transformation during the cooling of Ti-47Al-2Cr-2Nb-xRu(x=0,0.1,0.5,1.0,at.%)alloys was *** results show that Ru tends to segregate in the interdendritic region during solidification,and therefore,refines the as-cast microstructure of the *** aβ-stabilizer,Ru does not induce a novel solidification reaction but maintains the peritectic reaction of L+β→α.An excessive Ru content would cause the formation of(γ+τ1+B2)and(α+γ+τ1+B2)phase regions below 1,250°*** precipitation ofτ1-containing mixture is attributed to the Ru-segregation,which inhibits the reaction ofα→γand facilitates the formation of B2 *** discontinuous coarsening ofγphase and blockτ1 phase formed alternately in a manner of analogous eutectoid decomposition within B2 *** addition,the effect of Ru content on compression property of the alloys was *** yield strength increases up to 427 MPa at 800°C with the addition of 1.0at.%Ru,which is mainly due to the solution strengthening effect of Ru.

关键词： TiAl alloy solidification path microstructure phase transformation yield strength