High-Temperature Compressive Resistance and Mechanical Properties Improvement of Strain-Induced Melt Activation-Processed Al-Mg-Si Aluminum Alloy

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1 metals Article High-Temperature Compressive Resistance Mechanical Properties Improvement Stra-Induced Melt Activation-Processed Al-Mg-Si Alumum Alloy Chia-Wei L, Fei-Yi Hung * Truan-Sheng Lui Department Materials Science Engeerg, National Cheng Kung University, Taan 701, Taiwan; qqkm0526@gmail.com (C.-W.L.); luits@mail.ncku.edu.tw (T.-S.L.) * Correspondence: fyhung@mail.ncku.edu.tw; Tel.: (ext ); Fax: Academic Editor: Nong Gao Received: 13 June 2016; Accepted: 21 July 2016; Published: 5 August 2016 Abstract: Even though high-temperature formability Al can be enhanced by stra-duced melt activation (SIMA) process, mechanical formed are necessary for estimation. In this research, a modified two-step SIMA () process that omits cold workg step traditional SIMA process is adopted for 6066 Al-Mg-Si alloy to obta globular s with a short-duration salt bath. high-temperature compressive resistance mechanical vestigated. subjected to artificial agg to improve ir mechanical. results show that process can reduce compression loadg by about 35%. High-temperature compressive resistance can be reduced by process. After high-temperature compression, mechanical significantly improved. Furrmore, artificial agg can be used to enhance formed via process. After artificial agg, mechanical are comparable to those general artificially-aged materials. Keywords: alumum alloy; Stra-Induced Melt Activation (SIMA); mechanical 1. Introduction 6xxx series Al, a series precipitation-hardened Al, are widely used Al alloy, used this study, has a strength that is higher than that great majority or this series due to its Cu Mn addition excess Si [1,2]. This alloy is widely applied automobile dustry, bicycle dustry, architecture components, due to its high strength low density. Even though Cu Mn crease strength, y decrease formability. In order to promote formability, stra-duced melt activation (SIMA) process is used for formg at high temperatures. SIMA process is a semi-solid process, which materials are manufactured at temperatures solid-liquid coexistence. fished products have a near-net shape advantage [3 5]. SIMA process has great potential due to its low cost high stability [6 10]. 1a shows procedure two-step SIMA () process proposed this study. steps are: (1) castg, which produces a dendritic structure; (2) hot extrusion, which distegrates itial structure troduces sufficient stra energy to alloy; (3) salt bath, which makes material recrystallize partially melt at temperatures solid-liquid coexistence. is defed as a two-step process because castg materials are via only two steps to obta globular s. two major differences between traditional SIMA process process are: (1) proposed process uses severe hot extrusion stead cold work to troduce a large amount stra energy; (2) ; doi: /met

2 are: (1) proposed process uses severe hot extrusion stead cold work to troduce a large proposed amount SIMA process stra energy; uses a salt bath (2) stead proposed ansima air furnace process to improve uses a salt g bath stead uniformity an air furnace reduce g to improve time. g globular uniformity evolution reduce for g proposed time. globular process evolution is shownfor proposed 1b [11]. process is shown 1b [11] (a) (a) Procedure Procedure process process (b) formation (b) formation steps steps globular globular s s process. process. In our previous study [11], high-temperature deformation resistance formg behavior In our previous study [11], high temperature deformation resistance formg behavior vestigated. improvement high-temperature formability vestigated. improvement high temperature formability subjected to process confirmed. However, mechanical subjected to process confirmed. However, mechanical formed after process not examed. In this research, high-temperature formed after process not examed. In this research, high temperature compressibility improvement mechanical are vestigated. compressibility improvement mechanical are High-temperature compressibility is evaluated usg high-temperature compression. compression vestigated. High temperature compressibility is evaluated usg high temperature compression. deformation mechanism is also vestigated. mechanical compression deformation mechanism is also vestigated. mechanical are vestigated improved via artificial agg (). are vestigated improved via artificial agg (). 2. Materials Methods 2. Materials Methods material used this study extruded 6066 Al alloy. Its composition, determed usg material used this study extruded 6066 Al alloy. Its composition, determed usg a glow discharge spectrometer, is shown Table 1. Six-ch (15.24 cm) diameter castg materials glow discharge spectrometer, is shown Table 1. Six ch (15.24 cm) diameter castg materials extruded with dimensions 52 mm (width) ˆ 3 mm (thickness) 75 mm (width) ˆ 9 mm extruded with dimensions 52 mm (width) mm (thickness) 75 mm (width) mm (thickness). extrusion ratio 27:1 true stra 3.3. as-extruded alloy is denoted (thickness). extrusion ratio 27:1 true stra 3.3. alloy is as F. denoted as F.

3 Table 1. Composition 6066 Al alloy. Table 1. Composition 6066 Al alloy. Element Element Mg Mg Si Si Cu Cu Mn Mn Fe Fe Cr Cr Al Al Mass % Mass % Bal. Bal. salt bath for spheroidized formation conducted at 620 C salt bath for spheroidized formation conducted at 620 C for 10 m n for 10 m n cooled down by quenchg water. s spheroidized uniformly fraction cooled down by quenchg water. s spheroidized uniformly fraction liquid liquid phases high with se salt bath settgs. material deformed severely, or phases high with se salt bath settgs. material deformed severely, or partially melted partially melted severely, when temperature severely, when temperature higher than 620 C. higher than 620 C. alloy subjected to this salt bath is denoted as S10. alloy subjected to this salt bath is denoted Alumum as S10. are ten fully annealed for subsequent manufacturg. refore, test alloy Alumum this study are fully ten annealed fully annealed for comparison for subsequent with processed manufacturg. specimens. refore, In full test alloyannealg this study, fully F annealed ed to for 420 comparison with -processed specimens. In full annealg, F ed to 420 C C for 2 h, cooled to 220 C for 2 h, cooled to 220 C at a coolg rate 25 C/m, n cooled a furnace to room temperature. fully annealed at6066 a coolg Al alloy rate is denoted 25 C/m, as O. n cooled a furnace to room temperature. fully annealed 6066 Al alloy is denoted as O. microstructural characteristics size size analyzed analyzed usg usg optical optical microscopy (OM). (OM). specimens specimens polished polished usg SIC usg papers SIC papers from 80# from to80# 5000# to 5000# ( ( number number before before # means # means how many how hard many particles hard particles per square per square ch), ch), Al2O3 Al 2 O 3 aqueous aqueous suspension suspension ( μm), µm), SiO2 SiO 2 polishg suspension etched usg Keller s reagent. liquid fraction polishg suspension etched usg Keller s reagent. liquid fraction lower-meltg-pot lower meltg pot second phases measured usg ImageJ (National Institetes Health, Java second phases measured usg ImageJ (National Institetes Health, Java 1.8.0_60, New York, 1.8.0_60, New York, NY, USA) stware. Two shape parameters, x z, defed for NY, USA) stware. Two shape parameters, x z, defed for degree spheroidization [5]. degree spheroidization [5]. In 2a c, A represent major axis, mor axis, perimeter, In area 2, a, b, a c,, Arespectively. represent Accordg major axis, to mor defitions axis, perimeter, x = (b/a) z area = (4πA)/c a, respectively. 2, x is ratio Accordg mor to axis defitions to major x = (b/a) axis z z becomes = (4πA)/c closer 2, x isto 1 as ratio shape becomes mor axis more tocircular. major As axis x z becomes z become closer closer to 1 as to 1, shape s becomes more more circular. equi axial As x z become degree closer spheroidization to 1, s become creases. more equi-axial degree spheroidization creases Parameters Parameters spheroidization degree degree defition. defition. matrix globular boundaries evaluated usg nano dentation to underst matrix globular distribution boundaries evaluated usg. nano-dentation A triangular to underst pyramidal diamond probe distribution used for nano dentation.. Ameasurement triangular pyramidal conditions diamond a drift probe velocity used for nano-dentation nm/s a depth measurement 800 nm. space conditions between measurement a drift velocity pots μm. nm/s a depth In 800 nm. high temperature space between compression measurement test, pots 5, µm. fully annealed, In high-temperature tested to compression compare ir test, high temperature as-extruded formability., fully-annealed compression, ratio is defed as R% = (t0 tf)/t0, testedwhere to compare t0 is thickness ir high-temperature itial sheet formability. (9 mm) tf is compression thickness ratioafter is defed compression. as R% = specimens (t 0 t for compression had dimensions 40 mm (length) 20 mm f )/t 0, where t 0 is thickness itial sheet (9 mm) t (width) 9 mm (thickness). compression temperature set as 600 C compression f is thickness after compression. specimens for compression had dimensions rate set as 20 mm/m. compressive loadgs different materials estimated 40 mm (length) ˆ 20 mm (width) ˆ 9 mm (thickness). compression temperature set as 600 C compared as compression ratio reached 50%. When compression ratio is higher, compression rate set as 20 mm/m. compressive loadgs different materials deformation resistance is lower, which dicates better high temperature formability [12]. estimated compared as compression ratio reached 50%. When compression ratio is specimens to a compression ratio 50% used furr experiments for higher, deformation resistance is lower, which dicates better high-temperature formability [12]. specimens to a compression ratio 50% used furr experiments for improvg mechanical. Specimens subjected to compression are marked with prefix C-.

4 improvg improvg mechanical mechanical.. Specimens Specimens subjected subjected to to compression compression are are marked marked with with prefix C. prefix C. Fally, order to confirm that mechanical Fally, order order to to confirm confirm that that mechanical mechanical can be enhanced, adopted. cludes solution be enhanced, adopted. cludes can be enhanced, adopted. cludes solution solution artificial agg. Solution temperatures 530 C 550 C used this research. artificial agg. Solution temperatures 530 C 550 C artificial agg. Solution temperatures 530 C 550 C used used this this Specimens subjected to to are marked are suffix or. research. or suffix research. Specimens Specimens subjected subjected to are marked marked suffix 530 or 550. specimens measured usg a Rockwell tester tested specimens specimens measured measured usg usg aa Rockwell Rockwell tester tester usg a universal tester. dimensions test specimen are shown 3. tested usg a universal tester. dimensions test specimen tested usg a universal tester. dimensions test specimen are are specimen prepared by a millg mache for thng wire cuttg forfor shapg. shown 3. specimen prepared by a millg mache thng wire shown 3. specimen prepared by a millg mache for thng wire 3 Each itial stra shapg. velocity 1.67 ˆ 10 3 (crosshead velocity 1 mm/m). 1 cuttg cuttg for for shapg. itial itial stra stra velocity velocity (crosshead (crosshead velocity velocity 1 datum Each average from at least three testg samples. mm/m). datum average from at least three testg samples. mm/m). Each datum average from at least three testg samples. 3. test specimen. Dimensions Dimensions Dimensions test test specimen. specimen Results Discussion Discussion 3. Results Results Discussion 3.1. Characteristics 3.1. Microstructure 3.1. Microstructure Microstructure Characteristics Characteristics shows microstructures. typical 444 shows shows microstructures microstructures as-extruded.. typical typical extrusion microstructure can be seen metallography, as shown extrusion microstructure can be seen metallography as-extruded, as shown extrusion microstructure can be seen metallography, as shown 4a. Dynamic recrystallization only occurred parts F; recrystallized size only occurred parts F; F;recrystallized size about 4a. 4a.Dynamic Dynamicrecrystallization recrystallization only occurred parts recrystallized size about μm. Gras aa salt bath for µm.5 8 Gras spheroidized uniformlyuniformly after a saltafter bath for 10 m. about 5 8 μm. Gras spheroidized spheroidized uniformly after salt bath foraverage 10 m. m.globular average average globular size about 78 μm. shape parameters x z , respectively. size about shape parameters x z 0.62 z0.65, globular 78 sizeµm. about 78 μm. shape parameters x respectively , respectively. (F) (b) (S10) Microstructures Microstructures (a) (a) as-extruded (F) (F) (b) (b) (S10). (S10). 4. Microstructures (a) distribution distribution elements elements S10 S10 analyzed analyzed usg usg electron electron probe probe microanalysis microanalysis (EPMA) (EPMA) distribution elements S10 analyzed usg electron probe microanalysis (EPMA) (JEOL, (JEOL, Peabody, Peabody, MA, MA, USA). USA). results results are are shown shown After After aa salt salt bath, bath, Mg, Mg, Si, Si, Cu Cu (JEOL, Peabody, MA, USA).boundaries results are shown a 5. After a salt bath, Mg, Si, Cu located at formed network structure, but Mn, Fe, located at boundaries formed a network structure, but Mn, Fe, Cr Cr just just located at boundaries formed a network structure, but Mn, Fe, Cr just aggregated

5 aggregated formed a particle-shaped formed a particle shaped phase due phase to due meltg to pot meltg pot Mn-rich Mn rich phase beg phase higher beg than aggregated higher 620than C [13]. 620 formed C [13]. phases a particle shaped phases at globular at globular boundaries phase boundaries due to are composed meltg are composed pot eutectic Mn rich eutectic phase phase phase Al beg Al Al higher 2 Cu, Al2Cu, than eutectic 620 C eutectic [13]. phase phase phases Al Al at Mg globular 2 Si, Mg2Si, boundaries eutectic eutectic are phase composed phase Al Al Si. eutectic Si. meltg phase meltg pots Al pots se Al2Cu, eutectic se eutectic phases are phases below are Al 620 below C Mg2Si,, 620 thus, C, y thus, eutectic melted y phase melted penetrated Al penetrated to Si. globular to meltg pots globular boundaries. se boundaries. eutectic phases are below 620 C, thus, y melted penetrated to globular boundaries. 5. Elemental distribution alloy (S10) obtaed usg EPMA Elemental Elemental distribution distribution alloy alloy (S10) (S10) obtaed obtaed usg usg EPMA. EPMA. nano dentation data for S10 are shown 6. same results obtaed for five samples. nano-dentation nano dentation spheroidized data for S10 boundaries, are shown abundant 6. Cu, same Mg, results Si, are much obtaed harder for five than samples. ternal s. spheroidized This proves that boundaries, abundant boundaries Cu, Cu, Mg, Mg, Si, are Si, much alloy are much are harder harder than than ternal brittle ternal s. parts s. This proves material. This proves thatwhen that a boundaries boundaries alloy is defomed, alloy deformation are alloy hard are should brittle hard be parts where brittle stress parts material. concentration When material. occurs. a alloy a is defomed, alloy is defomed, deformation should deformation be where should stress be concentration where stress concentration occurs. occurs. 6. Hardness distribution evaluated usg nano dentation Hardness distribution evaluated usg nano-dentation. nano dentation High Temperature Compressive Resistance Alloy High-Temperature High Temperature For compression Compressive Compressive test at Resistance Resistance 600 C, 7 Alloy Alloy shows compression loadg at a 50% compression For For compression ratio compression for various test test atmaterials. 600 C, 600 C, It can 7 be shows seen 7 that shows compression S10 has compression loadg lowest at compression a loadg 50% compression at loadg. a 50% ratio compression Full annealg for various ratio reduced materials. for various compression It can materials. be seen loadg that It can S10 by be has only seen about that lowest S10 9% has compression but lowest loadg. compression process Full annealg reduced loadg. it reduced Full by about annealg compression 35% compared reduced loadg compression with by that only loadg about 9% by only but about. 9% This but process proves that reduced process it by about reduced process 35% it compared by is beneficial about 35% with for compared that enhancg with as-extruded high temperature that. This compressibility. proves. that This proves compressive that process resistance beneficial process for is beneficial alloy for enhancg smallest. high temperature compressibility. compressive resistance alloy smallest.

6 6 12 enhancg high-temperature compressibility. compressive resistance alloy Metals smallest. 2016, 6, Deformation resistance several materials. 7. Deformation resistance several materials. shows microstructures. It can be seen that after high temperature 8 shows compression, microstructures globular s became flat oval shaped,. It as can shown be seen that after 8a. high-temperature Under high temperature large magnification compression, ( globular 8b), it s can be became seen that flat origal oval shaped, oval-shaped, broad as shown boundaries 8a. Under large 8b), it can be seen that origal broad boundaries magnification vanished ( after compression. 8b), it can be Only seen that Mn rich origal particle broad phases existed boundaries at vanished after Only Mn-rich particle at boundaries vanished ternal after s. compression. This resulted Only Mn rich from particle low meltg pot phases existed phases at at low-meltg-pot boundaries boundaries meltg at 600 ternal C flowg durg high temperature compression. C s. This resulted from low meltg pot phases at boundaries meltg at 600 C flowg durg high-temperature high temperature compression. 8. Microstructure alloy at (a) small (b) large magnification. 8. Microstructure alloy at (a) small (b) large magnification. 9 shows elemental distribution. It shows that Cu, Mg, Si 9 shows shows no longer elemental elemental located distribution distribution at globular boundaries.. after It shows It high temperature shows that that Cu, Mg, Cu, compression. Mg, Si Si no y longer diffused no located longer at located solid soluted globular at to globular boundaries matrix durg after boundaries high-temperature hot temperature after high temperature compression. In y compression. contrast, diffused Mn, y Fe, solid-soluted diffused Cr still aggregated to solid soluted matrix to durg formed hot-temperature matrix a particle shaped durg hot temperature compression. phase. In compression. contrast, Mn, Fe, In contrast, Cr still Mn, aggregated Fe, Cr still formed aggregated a particle-shaped formed a phase. particle shaped phase.

7 Elemental Elementaldistribution distribution alloy alloy(c S) (C-S)obtaed obtaedusg usgepma. EPMA Mechanical MechanicalProperties PropertiesImprovement Improvement Formg FormgAlloys Alloys In ensure that formed products are suitable for applications, mechanical In order order totoensure that formed products are suitable for applications, mechanical vestigated., mostused commonly vestigated., most commonly method used method for strengng Al, is used this study. 10 shows for strengng 6xxx series Al 6xxx,series is used this study. 10 shows data data 11a shows data treated 11a shows data -treated materials. Hardness data materials. data showthat High-temperature show that Hardness values as-extruded values are similar. are similar. High temperature compression significantly enhanced. compression significantly enhanced. After, After all specimens, all specimens creased obviously. Hardness creased with creasg creased obviously. Hardness creased with creasg solution temperature due to solution limit to solution beg enhanced by creased solution solution begtemperature enhanced bydue creased solutionlimit temperature. temperature. is slightly lower than that is slightly lower than that as-extruded after. Strength data. Strength trends are similar tocreased those after trends after are similar to those data.data strength specimens data.. strength specimens creased after. strength strength slightly lower (by about10 20 MPa) than that slightly (by about MPa) than ultimate as-extruded.lower ultimate strength (UTS)that. reached about MPa. strength (UTS) reached aboutmaterials after MPa. thatis This shows that strength formg This shows highstrength enough for formg materials after is high enough for common applications. common Metals 2016,applications. 6, Elongation data are shown 11b. elongation is much lower than that. Elongation can be improved to about 23% uniform elongation (UE) 27% total elongation (TE) after compression at 600 C. enhancement elongation is majorly due to hard brittle phases located at globular boundaries composed Al, Mg, Si, Cu diffused to matrix After, elongation creased with decreasg solution temperature. Uniform elongation reached about 12% total elongation reached 16% when solution temperature 530 C. Even though elongation quite low, high temperature compression improved it. mechanical can thus be improved by high temperature compression. Strength can reach more than 400 MPa elongation can reach more than 10% after appropriate. 10. Hardness data specimens. Elongation data are shown 11b. elongation is much lower than that as-extruded. Elongation can be improved to about 23% uniform elongation (UE) 27% total elongation (TE) after compression at 600 C. enhancement elongation is majorly due

8 8 12 to hard brittle phases located at globular boundaries composed Al, Mg, Si, Cu diffused to matrix After, elongation creased with decreasg solution temperature. Uniform elongation reached about 12% total elongation reached 16% when solution temperature 530 C. Even though elongation quite low, high-temperature compression improved it. mechanical can thus be improved by high-temperature compression. Strength can reach more than 400 MPa elongation can 10. reach Hardness more than data 10% specimens. after appropriate. 11. Mechanical specimens: (a) strength (b) elongation. 11. Mechanical specimens: (a) strength (b) elongation. 12 shows microstructures after. It shows that origal globular s grew durg solution, as shown 12c,d. microstructure --treated as-extruded remaed as fe recrystallized s, as show 12e,f. level precipitation strengng as-extruded should be similar because ir compositions

9 shows microstructures after. It 12 shows microstructures after. It shows that origal globular s grew durg shows that origal globular s grew durg solution, as shown 12c,d. microstructure treated solution, as shown 12c,d. microstructure treated remaed as fe recrystallized s, as show 12e,f. level precipitation Metals 2016, 6, remaed as fe recrystallized s, as show 12e,f. level precipitation strengng should be similar because strengng should be similar because ir compositions conditions are same. slightly different mechanical ir compositions conditions conditions are different same. slightly different mechanical are are same. slightly mechanical are due to due to size accordg to Hall Petch ory [14,15]. After, are due to size accordg to Hall Petch ory [14,15]. After, size accordg to Hall-Petch ory [14,15]. After, strength as-extruded strength higher than that formg due to former s strength higher higher than that due formg due tohowever, former s than that to former s fe s. fe s. However, high densityformg boundaries treated fe s. However, high density boundaries treated high density boundaries --treated as-extruded slightly decreased elongation slightly decreased elongation because dislocation slippg is restricted by boundaries. slightly dislocation decreased slippg elongation because dislocation slippg refore, is restricted by boundaries. because is restricted boundaries. that elongation refore, elongation by formg is higher than treated refore, elongation formg is higher than that treated formg is higher than that --treated as-extruded... Morphologies (a) C S10/ 530; (b) C S10/550; (c) C F/530; (d) C F/ Morphologies (a) C-S10/ 530 ; (b) C-S10/550 ; (c) C-F/530 ; (d) C-F/ Morphologies (a) C S10/ 530; (b) C S10/550; (c) C F/530; (d) C F/ shows elemental distribution after 13 elemental distribution after 13shows shows elemental distribution after.. It shows that all elements distributed uniformly. This proves that It shows that all elements distributed uniformly.uniformly. This proves thatproves made Cu,. It shows that all elements distributed This that made Cu, Mg, Si solid solute completely precipitate. Mg, solid-solute completelycompletely precipitate. made Cu,SiMg, Si solid solute precipitate. 13. Elemental distribution alloy after (C S10/530) alloy alloyafter after (C-S10/ (C S10/ )) 13. Elemental distribution obtaed usg EPMA. obtaed usg EPMA. fracture mechanism above specimens can be terpreted from s s 14a 15a show tergranular fracture characteristics. low-meltg-pot phases melted, penetrated, solidified at globular boundaries, resultg boundary beg more brittle harder than matrix. This led to stress concentration generation

10 10 13 fracture mechanism above specimens can be terpreted from s s 14a 15a show tergranular fracture characteristics. low meltg pot phases melted, penetrated, solidified at globular boundaries, resultg Metals 2016, 6, boundary beg more brittle harder than matrix. This led to stress concentration generation cracks. cracks itiated at boundaries connected cracks. or, cracksleadg itiatedtoattergranular boundaries connected with each or, leadg tergranular with each fracture. In contrast, characteristic dimpletractures fracture. In contrast, characteristic dimple fractures found on fracture surfaces found on fracture surfaces treated --treated, as shown 14c f.caused Micro-void, as shown 14c f. Micro void coalescence ductile fracture se coalescence ductile fracture caused se dimple fractures. sub-surface morphologies dimple fractures. sub surface morphologies treated --treated did arenot shown are shown 15b d. Intergranular fractures appear Intergranular fractures did not phases appear because brittle low-meltg-pot phases because15b d. brittle low meltg pot vanishedafter high temperature compression. vanished after high-temperature compression. refore, good mechanical obtaed. refore, good mechanical obtaed Fracture (c)(c) C S10/ 530; (d); C S10/ 550; (e) C F/530; (f) Fracturesurfaces surfaces(a) (a)s10; S10;(b) (b)c S10; C-S10; C-S10/ 530 (d) C-S10/550 ; (e) C-F/530 ; C F/. (f) 550 C-F/. 550 Brittle hard phases located at boundaries disappeared after high-temperature compression, improvg elongation. Total elongation creased to about 30%. After, strength formg reached about 430 MPa. strength such is slightly less than that --treated as-extruded (by about 20 MPa) its elongation can be slightly higher than that. mechanical --treated formg are sufficient for common applications.

11 Sub-surfaces Sub surfaces (a) (a) S10; S10; (b) (b) C-S10; C S10; (c) (c) C-S10/ C S10/530; C S10/ ; (d) C-S10/ Conclusions Brittle hard phases located at boundaries disappeared after high temperature compression, improvg elongation. Total elongation creased to about 30%. After (1) Globular, s obtaed strength usg formg process. After areached salt bath, about s 430 MPa. became strength globular such Cu, Mg, is slightly Si less major than that elements treated distributed on globular (by boundaries. about 20 MPa) globular its elongation boundaries can be harder slightly thanhigher Al matrix. than that. mechanical treated (2) High-temperature formg compressive resistance are sufficient canfor becommon reduced applications. by process. With a 50% compression ratio, process decreased compression loadg by about 35%. After 4. Conclusions high-temperature compression, Cu, Mg, Si no longer located at globular boundaries. (1) Globular s obtaed usg process. After a salt bath, s (3) High-temperature compression can improve elongation. mechanical became globular Cu, Mg, Si major elements distributed on globular can be enhanced by. mechanical are boundaries. globular boundaries harder than Al matrix. sufficient for common applications. (2) High temperature compressive resistance can be reduced by process. With a Acknowledgments: 50% compression ratio, authors are grateful process to Instrument decreased Center compression National loadg Chengby Kung about University 35%. After high temperature National Sciencecompression, Council Taiwan Cu, (NSC Mg, MOST E MY2) Si no longer located forat ir fancial support. globular Author boundaries. Contributions: Chia-Wei L, designed experiments, performed experiments, analyzed data wrote (3) High temperature paper; Fei-Yi Hungcompression Truan-Sheng can Lui improve gave suggestions elongation for improvg experiments. analysis. mechanical Conflicts Interest: authors declare no conflict can be terest. enhanced by. mechanical are sufficient for common applications. References Acknowledgments: authors are grateful to Instrument Center National Cheng Kung University 1. Hatch, J.E. Alumum: Properties Physical Metallurgy; ASM International: Materials Park, OH, USA, 1984; National Science Council Taiwan (NSC MOST E MY2) for ir fancial support. Volume 1, p. 50. Author 2. Zhen, Contributions: L.; Fei, W.D.; Chia Wei Kang, S.B.; L, Kim, designed H.W. Precipitation experiments, behavior performed Al-Mg-Si experiments, with high analyzed silicon content. data wrote J. Mater. Sci. paper; 1997, Fei Yi 32, Hung Truan Sheng Lui gave suggestions for improvg experiments analysis. 3. Fan, Z. Semisolid metal processg. Int. Mater. Rev. 2002, 47, [CrossRef] Conflicts Interest: authors declare no conflict terest.

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