A 17 vol%SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed)at a very high welding speed of 2000 mm/min for the first time.Microstructural observation indicated th...A 17 vol%SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed)at a very high welding speed of 2000 mm/min for the first time.Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed,due to the significantly reduced peak temperature and duration at high temperature.Therefore,prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed,which was similar to that of the nugget zone.Furthermore,the ultimate tensile strength of the joint was as high as 369 MPa,which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa).This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.展开更多
Amorphous Al2 O3-reinforced Al composite(am-Al2 O3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al2 O3 at high temperatures will result in ...Amorphous Al2 O3-reinforced Al composite(am-Al2 O3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al2 O3 at high temperatures will result in serious strength loss.Aiming at this unsolved problem,in this study,high-temperature Al materials with enhanced thermal stability were developed through introducing more thermally stable nano-sized particles via high-temperature pre-treatment of ultrafine A1 powders.It was found that the pre-treatment at ≤550℃ could introduce a few Al2 O3 in the Al matrix and increase the strength of the composites,but the strength was still below that of am-Al2 O3/Al because without being pinned firmly,grain boundaries(GBs) were softened at high temperature and intergranular fracture happened.When the pre-treatment was carried out at 600℃,nitridation and oxidation processes happened simultaneously,producing large numbers of intergranular(AlN+γ-Al2 O3) particles.GB sliding and intergranular fracture were suppressed;therefore,higher strength than that of am-Al2 O3/Al was realized.Furthermore,the(AIN+γ-Al2 O3)/Al exhibited more superior thermal stability compared to amAl2 O3/Al for annealing treatment at 580℃ for 8 h.Therefore,an effective way to fabricate high-temperature Al composite with enhanced thermal stability was developed in this study.展开更多
基金supported by the National Key R&D Program of China (No. 2017YFB0703104)National Natural Science Foundation of China (Nos. 51331008 and 51671191)
文摘A 17 vol%SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed)at a very high welding speed of 2000 mm/min for the first time.Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed,due to the significantly reduced peak temperature and duration at high temperature.Therefore,prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed,which was similar to that of the nugget zone.Furthermore,the ultimate tensile strength of the joint was as high as 369 MPa,which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa).This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.
基金supported by the National Natural Science Foundation of China (Nos. U1508216 and 51771194)the Youth Innovation Promotion Association CAS (No. 2016179)the National Key R&D Program of China (No. 2017YFB0703104)。
文摘Amorphous Al2 O3-reinforced Al composite(am-Al2 O3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al2 O3 at high temperatures will result in serious strength loss.Aiming at this unsolved problem,in this study,high-temperature Al materials with enhanced thermal stability were developed through introducing more thermally stable nano-sized particles via high-temperature pre-treatment of ultrafine A1 powders.It was found that the pre-treatment at ≤550℃ could introduce a few Al2 O3 in the Al matrix and increase the strength of the composites,but the strength was still below that of am-Al2 O3/Al because without being pinned firmly,grain boundaries(GBs) were softened at high temperature and intergranular fracture happened.When the pre-treatment was carried out at 600℃,nitridation and oxidation processes happened simultaneously,producing large numbers of intergranular(AlN+γ-Al2 O3) particles.GB sliding and intergranular fracture were suppressed;therefore,higher strength than that of am-Al2 O3/Al was realized.Furthermore,the(AIN+γ-Al2 O3)/Al exhibited more superior thermal stability compared to amAl2 O3/Al for annealing treatment at 580℃ for 8 h.Therefore,an effective way to fabricate high-temperature Al composite with enhanced thermal stability was developed in this study.
