The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°C.Mg element in the Al-Mg a...The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°C.Mg element in the Al-Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al-Mg alloy powders,thus,promoting the reactions.In the samples with Mg contents varying from 5.09 wt.%to 25.93 wt.%,the first-formed intermetallic compound was Al_(18)Ti_(2)Mg_(3),and then Al_(3)Ti generated at the Al_(18)Ti_(2)Mg_(3)/Ti interface.Since the Mg content in the Al-Mg melts decreased during the subsequent heat-ing process,the previously formed Al_(18)Ti_(2)Mg_(3)in the Ti/Al-5.09Mg sample transformed into Al_(3)Ti accom-panied by the reaction of Al with Ti to newly form Al_(3)Ti,generating a single Al_(3)Ti phase.In contrast,the new formation of Al_(3)Ti and its transformation to Al_(18)Ti_(2)Mg_(3)proceeded continuously in the Ti/Al-13.54Mg and Ti/Al-25.94Mg samples,resulting in a mixture of Al_(18)Ti_(2)Mg_(3)and a little Al_(3)Ti residue.In the Ti/Al-40.54Mg sample,Al_(3)Ti was the unique reaction product throughout the heating process.The final Al_(3)Ti particles in the Ti/Al-5.09Mg sample were in a blocky shape,while they were in a plate-like form in the Ti/Al-40.54Mg sample,which was caused by the enhanced growth anisotropy due to the de-creased interfacial energy between Al_(3)Ti particles and Al-Mg melts with the increase of Mg content.A twin plane re-entrant mechanism was suggested for the growth of Al_(18)Ti_(2)Mg_(3)particles,weakening the anisotropic growth caused by the directional supply of Ti atoms,and contributing to the blocky mor-phology of Al_(18)Ti_(2)Mg_(3)particles.In addition,the volume difference between the formed Al_(18)Ti_(2)Mg_(3)and consumed Ti was greater than that between the Al_(3)Ti and Ti,and the Al_(18)Ti_(2)Mg_(3)has worse plasticity than the Al_(3)Ti,resulting in the Al_(18)Ti_(2)Mg_(3)reaction product fracturing more easily during thickening,thus forming a petal-like structure,but the Al_(3)Ti product being in an almost continuous layer.展开更多
The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital imag...The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital image correlation（3D-DIC） technique was applied to obtaining the further insight into the spatiotemporal characteristics, in particular the influence of Mg content on deformation behaviors. Mg content has a pronounced effect on serration characteristics, including the serration type and amplitude; Mg content tends to weaken the spatial correlation of the propagative bands. Additionally, the serration amplitude linearly increases with the maximum PLC band strain; high Mg content generates a higher PLC band strain at a given serration amplitude compared with low Mg content. Mg content is found to be effective to enhance the serration amplitude, the maximum PLC band strain and also the amount of elastic shrinkage outside PLC bands.展开更多
Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined ...Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.展开更多
To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properti...To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.展开更多
The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model ...The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.展开更多
基金the National Key Re-search and Development Program(Grant No.2018YFB2001800)the National Natural Science Foundation of China(Grant No.51564035).
文摘The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°C.Mg element in the Al-Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al-Mg alloy powders,thus,promoting the reactions.In the samples with Mg contents varying from 5.09 wt.%to 25.93 wt.%,the first-formed intermetallic compound was Al_(18)Ti_(2)Mg_(3),and then Al_(3)Ti generated at the Al_(18)Ti_(2)Mg_(3)/Ti interface.Since the Mg content in the Al-Mg melts decreased during the subsequent heat-ing process,the previously formed Al_(18)Ti_(2)Mg_(3)in the Ti/Al-5.09Mg sample transformed into Al_(3)Ti accom-panied by the reaction of Al with Ti to newly form Al_(3)Ti,generating a single Al_(3)Ti phase.In contrast,the new formation of Al_(3)Ti and its transformation to Al_(18)Ti_(2)Mg_(3)proceeded continuously in the Ti/Al-13.54Mg and Ti/Al-25.94Mg samples,resulting in a mixture of Al_(18)Ti_(2)Mg_(3)and a little Al_(3)Ti residue.In the Ti/Al-40.54Mg sample,Al_(3)Ti was the unique reaction product throughout the heating process.The final Al_(3)Ti particles in the Ti/Al-5.09Mg sample were in a blocky shape,while they were in a plate-like form in the Ti/Al-40.54Mg sample,which was caused by the enhanced growth anisotropy due to the de-creased interfacial energy between Al_(3)Ti particles and Al-Mg melts with the increase of Mg content.A twin plane re-entrant mechanism was suggested for the growth of Al_(18)Ti_(2)Mg_(3)particles,weakening the anisotropic growth caused by the directional supply of Ti atoms,and contributing to the blocky mor-phology of Al_(18)Ti_(2)Mg_(3)particles.In addition,the volume difference between the formed Al_(18)Ti_(2)Mg_(3)and consumed Ti was greater than that between the Al_(3)Ti and Ti,and the Al_(18)Ti_(2)Mg_(3)has worse plasticity than the Al_(3)Ti,resulting in the Al_(18)Ti_(2)Mg_(3)reaction product fracturing more easily during thickening,thus forming a petal-like structure,but the Al_(3)Ti product being in an almost continuous layer.
基金financial support received from the National Natural Science Foundation of China (NSFC) under Grant Nos. 11332010, 51571013, 51271174, 11472266 and 11428206
文摘The Portevin–Le Chatelier（PLC） effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital image correlation（3D-DIC） technique was applied to obtaining the further insight into the spatiotemporal characteristics, in particular the influence of Mg content on deformation behaviors. Mg content has a pronounced effect on serration characteristics, including the serration type and amplitude; Mg content tends to weaken the spatial correlation of the propagative bands. Additionally, the serration amplitude linearly increases with the maximum PLC band strain; high Mg content generates a higher PLC band strain at a given serration amplitude compared with low Mg content. Mg content is found to be effective to enhance the serration amplitude, the maximum PLC band strain and also the amount of elastic shrinkage outside PLC bands.
基金supported by the National Natural Science Foundation of China (Nos. 51674166, U1902220)the National Key R&D Program of China (No. 2021YFB3701303)。
文摘Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.
基金supported by the National Natural Science Foundation of China(Nos.51801079,52001140)the National Funds Through FCT of Portugal–Fundacao para a Ciência e a Tecnologia,under a scientific contract of 2021.04115.CEECIND,and the Projects of UIDB/00285/2020,and LA/0112/2020。
文摘To improve the processability and mechanical properties of the selective laser melting(SLM)low Sc content Al−Mg−Sc−Zr alloy,Mn was used to partially replace Mg.The processability,microstructure,and mechanical properties of the SLM-fabricated Al−Mg−Mn−Sc−Zr alloy were systematically investigated by density measurement,microstructure characterization,and tensile testing.The results revealed that dense samples could be obtained by adjusting the SLM process parameters.The alloy exhibited a fine equiaxed-columnar bimodal grain microstructure.The presence of primary Al3Sc andα-Al(Mn,Fe)Si particles contributed to the grain refinement of the alloy with an average grain size of 4.63μm.Upon aging treatment at 350°C for 2 h,the strength and elongation of the alloy were simultaneously improved due to the precipitation of Al3Sc nanoparticles and the formation of the 9R phase.This study demonstrates that the strength−plasticity trade-off of the aluminum alloy can be overcome by utilizing SLM technology and subsequent post-heat treatment to induce the formation of the long-period stacked ordered phase.
文摘The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.
