As-cast Al-Si alloys always face low ductility because of coarseα-Al grains and large lamellar eutectic Si.Although B-containing refiners and Sr modifiers could refine theα-Al grains and eutectic Si respec-tively,si...As-cast Al-Si alloys always face low ductility because of coarseα-Al grains and large lamellar eutectic Si.Although B-containing refiners and Sr modifiers could refine theα-Al grains and eutectic Si respec-tively,simultaneous addition leads to an invalid effect of Sr because B-containing refiner has a poison-ing effect(PE)on Sr modifier in the Al-10Si-B-Sr alloys.The present work achieves both refinement ofα-Al grains and modification of Si merely by the addition of 500 ppm La in Al-10Si-0.02B-0.015Sr alloy,which greatly enhances the ductility and tensile strength.Sr-B interaction in the Al-10Si-0.02B-0.015Sr melt results in a consumption of Sr by forming Sr-B intermetallic compound.CALPHAD-type calculations reveal that Sr concentration in liquid before eutectic reaction becomes a key parameter to estimate the alloying modification effect.The addition of La forms LaB 6 and thereby releases Sr to protect the Sr modification effect.First-principles calculations illustrate that both Sr and La are benefi-cial to the formation of twin boundaries in Si particles due to their negative formation energy of twin boundaries.The formed LaB 6 has a semicoherent interface withα-Al with the orientation relationship of[110]_(LaB6)//[110]_(Al) and(111)_(LaB6)//(111)_(Al),demonstrating that LaB 6 is an efficient nucleation site forα-Al,which contributes to the refinement ofα-Al in the Al-10Si-0.05La-0.02B-0.015Sr alloy.Our findings re-veal the micro-mechanism of refinement during the solidification process and develop an effective and simple way to obtain high-performance Al alloys.展开更多
The effect of Ce content(0–1.6 wt.%)on the modification of Mg_(2)Si phase in the as-cast Mg-5Al-2Si alloy was investigated.The original Chinese script type Mg_(2)Si phase was refined distinctly and transformed to dis...The effect of Ce content(0–1.6 wt.%)on the modification of Mg_(2)Si phase in the as-cast Mg-5Al-2Si alloy was investigated.The original Chinese script type Mg_(2)Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element.The length of Chinese script type Mg_(2)Si phase was reduced from 110 to 50μm with increasing Ce content to 1.6 wt.%.The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi_(2)phase,which could serve as the heterogeneous nucleation of Mg_(2)Si phase due to the small lattice mismatch of 7.97%.The modification of Mg_(2)Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg_(2)Si phase and CeSi_(2)promoted the nucleation of Mg_(2)Si phase.With increasing Ce content from 0 wt.%to 1.6 wt.%,the YS,UTS and EL at 150℃were improved from 67.7 MPa,91.2 MPa and 1.6%to 84.2 MPa,128 MPa and 7.5%,respectively.展开更多
Trace La element was introduced in Al-20Mg_(2)Si composites to regulate the microstructure and corrosion performance.The modification mechanism of trace La and the corrosion behavior of the newly developed composites ...Trace La element was introduced in Al-20Mg_(2)Si composites to regulate the microstructure and corrosion performance.The modification mechanism of trace La and the corrosion behavior of the newly developed composites were systematically investigated by thermal analysis,microstructural observations and electrochemical tests.Our study reveals that the addition of only 0.10%La can refine the size of the primary Mg_(2)Si phase from 77.6 to 26.7μm,modify its morphology from a coarse dendrite to a fine truncated octahedron and reduce the corrosion current density from 5.96μA cm^(-2) to 3.03μA cm^(-2).Trace La refines the primary Mg_(2)Si phase size by forming a tiny LaAlSi phase which can provide effective heterogeneous nuclei for the primary Mg_(2)Si phase during solidification.Excess La atoms can selectively adsorb on the{100}facets of the primary Mg_(2)Si phase and suppress the preferential growth of the Mg_(2)Si phase,eventually resulting in the morphological transition of the primary Mg_(2)Si phase from dendrite to truncated octahedron shape.The enhanced corrosion resistance of the La micro-alloyed Al-20Mg_(2)Si composites can be attributed to the formation of stronger protective surface oxide films and finer primary Mg_(2)Si phase.The protective oxide films can effectively hinder the penetration of the corrosive medium and the finer primary Mg_(2)Si phase can weaken the localized corrosion tendency of the Al-Mg_(2)Si composites.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.U2102212,51871138,and 51821001)the Shanghai Rising-Star Program(No.21QA1403200)the Shanghai Engineering Research Center for Metal Parts Green Remanufacture(No.19DZ2252900)from Shanghai Engineering Research Center Construction Project.
文摘As-cast Al-Si alloys always face low ductility because of coarseα-Al grains and large lamellar eutectic Si.Although B-containing refiners and Sr modifiers could refine theα-Al grains and eutectic Si respec-tively,simultaneous addition leads to an invalid effect of Sr because B-containing refiner has a poison-ing effect(PE)on Sr modifier in the Al-10Si-B-Sr alloys.The present work achieves both refinement ofα-Al grains and modification of Si merely by the addition of 500 ppm La in Al-10Si-0.02B-0.015Sr alloy,which greatly enhances the ductility and tensile strength.Sr-B interaction in the Al-10Si-0.02B-0.015Sr melt results in a consumption of Sr by forming Sr-B intermetallic compound.CALPHAD-type calculations reveal that Sr concentration in liquid before eutectic reaction becomes a key parameter to estimate the alloying modification effect.The addition of La forms LaB 6 and thereby releases Sr to protect the Sr modification effect.First-principles calculations illustrate that both Sr and La are benefi-cial to the formation of twin boundaries in Si particles due to their negative formation energy of twin boundaries.The formed LaB 6 has a semicoherent interface withα-Al with the orientation relationship of[110]_(LaB6)//[110]_(Al) and(111)_(LaB6)//(111)_(Al),demonstrating that LaB 6 is an efficient nucleation site forα-Al,which contributes to the refinement ofα-Al in the Al-10Si-0.05La-0.02B-0.015Sr alloy.Our findings re-veal the micro-mechanism of refinement during the solidification process and develop an effective and simple way to obtain high-performance Al alloys.
基金supported by the Major Science and Technology projects in Qinghai province (2018-GX-A1)Global Frontier Program through the Global Frontier Hybrid Interface Materials (GFHIM) of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (Grant No. 2013M3A6B1078874)+1 种基金funded by Shanghai Science and Technology Committee (Grant No. 18511109302)the National Natural Science Foundation of China (Grant No. 51825101)
文摘The effect of Ce content(0–1.6 wt.%)on the modification of Mg_(2)Si phase in the as-cast Mg-5Al-2Si alloy was investigated.The original Chinese script type Mg_(2)Si phase was refined distinctly and transformed to dispersive block shape gradually by adding Ce element.The length of Chinese script type Mg_(2)Si phase was reduced from 110 to 50μm with increasing Ce content to 1.6 wt.%.The results calculated by Pandat software indicated that the added Ce element first combined with Si to form CeSi_(2)phase,which could serve as the heterogeneous nucleation of Mg_(2)Si phase due to the small lattice mismatch of 7.97%.The modification of Mg_(2)Si phase was mainly attributed to the facts that Ce changed the growth steps of Mg_(2)Si phase and CeSi_(2)promoted the nucleation of Mg_(2)Si phase.With increasing Ce content from 0 wt.%to 1.6 wt.%,the YS,UTS and EL at 150℃were improved from 67.7 MPa,91.2 MPa and 1.6%to 84.2 MPa,128 MPa and 7.5%,respectively.
基金supported by the National Natural Science Foundation of China(Nos.52201051 and 52201295)。
文摘Trace La element was introduced in Al-20Mg_(2)Si composites to regulate the microstructure and corrosion performance.The modification mechanism of trace La and the corrosion behavior of the newly developed composites were systematically investigated by thermal analysis,microstructural observations and electrochemical tests.Our study reveals that the addition of only 0.10%La can refine the size of the primary Mg_(2)Si phase from 77.6 to 26.7μm,modify its morphology from a coarse dendrite to a fine truncated octahedron and reduce the corrosion current density from 5.96μA cm^(-2) to 3.03μA cm^(-2).Trace La refines the primary Mg_(2)Si phase size by forming a tiny LaAlSi phase which can provide effective heterogeneous nuclei for the primary Mg_(2)Si phase during solidification.Excess La atoms can selectively adsorb on the{100}facets of the primary Mg_(2)Si phase and suppress the preferential growth of the Mg_(2)Si phase,eventually resulting in the morphological transition of the primary Mg_(2)Si phase from dendrite to truncated octahedron shape.The enhanced corrosion resistance of the La micro-alloyed Al-20Mg_(2)Si composites can be attributed to the formation of stronger protective surface oxide films and finer primary Mg_(2)Si phase.The protective oxide films can effectively hinder the penetration of the corrosive medium and the finer primary Mg_(2)Si phase can weaken the localized corrosion tendency of the Al-Mg_(2)Si composites.
