Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered(LPSO)phase were prepared through heat treatment and a series of hot compression tests on these ...Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered(LPSO)phase were prepared through heat treatment and a series of hot compression tests on these materials were conducted to examine and evaluate the influence of LPSO on the hot compressive deformation behavior and deformation mechanisms at a given alloy composition.The values of activation energy for plastic flow(Qc)of the solution treated(without LPSO phase)and annealed alloys(with intragranular LPSO phase)were larger than that for pure Mg,indicating that the presence of a high amount of rare earth(RE)elements and LPSO in the Mg matrix significantly increases Qc.The Qcvalue of the annealed alloy was larger than that of the solution treated alloy at all the strain levels(223.3 vs.195.5 k J/mol in average)and the largest difference in Qcbetween the two alloys was recorded at the smallest strain of 0.1 where precipitation of LPSO during deformation was limited in the solution treated alloy.These observations imply that the formation of LPSO phase out of the RE-rich solid solution matrix during deformation increases Qc,but the increment is not so large.Analysis of the hot compressive data of the alloys with LPSO phase and the alloys with RE-rich solid solution matrix in literatures indicates the similarity of the effect of the LPSO and RE-rich solid solution matrix phases on Qcand high-temperature strength.展开更多
Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show tha...Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show that vanadium enriches around the boundary ofαphases with increasing annealing temperature to 973 K,andα′phases transform intoα+βat 973 K.The typicalα′martensite microstructure transforms to fine-scale equiaxed microstructure at 973 K and the equiaxed microstructure significantly coarsens with increasing annealing temperature to 1273 K.The SLM Ti-6Al-4V alloy annealed at 973 K exhibits a well-balanced combination of strength and ductility((1305±25)MPa and(37±3)%,respectively).展开更多
The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the...The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the extended-chain crystal(ECC)of the same polymer as nucleating agent.The crystallization of PBS with its ECC as nucleating agent in a wide temperature range(90–127°C)and the following melting behavior were studied.It is revealed that the melting point(Tm',for Tc≥113°C)and the annealing peak temperature(Ta',for Tc=90–100°C)show similar asymptotic behavior.Both Tm and Ta approach to a value of ca.3.3°C higher than the corresponding Tc when the crystallization time tc approaches the starting point.That is to say,the Hoffman-Weeks plot is parallel to Tm=Tc line.The crystallization line became parallel to the melting line when PBS was crystallized at Tc higher than 102°C.Based on these results,we propose that the parallel relationship and the intrinsic similarity between the Ta and the Tm observed at the two ends of the Tc range could be attributed to the metastable crystals formed at the beginning of crystallization.展开更多
基金financially supported by the Mid-Career Researcher Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology(NRF-2020R1A2C1008105)。
文摘Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered(LPSO)phase were prepared through heat treatment and a series of hot compression tests on these materials were conducted to examine and evaluate the influence of LPSO on the hot compressive deformation behavior and deformation mechanisms at a given alloy composition.The values of activation energy for plastic flow(Qc)of the solution treated(without LPSO phase)and annealed alloys(with intragranular LPSO phase)were larger than that for pure Mg,indicating that the presence of a high amount of rare earth(RE)elements and LPSO in the Mg matrix significantly increases Qc.The Qcvalue of the annealed alloy was larger than that of the solution treated alloy at all the strain levels(223.3 vs.195.5 k J/mol in average)and the largest difference in Qcbetween the two alloys was recorded at the smallest strain of 0.1 where precipitation of LPSO during deformation was limited in the solution treated alloy.These observations imply that the formation of LPSO phase out of the RE-rich solid solution matrix during deformation increases Qc,but the increment is not so large.Analysis of the hot compressive data of the alloys with LPSO phase and the alloys with RE-rich solid solution matrix in literatures indicates the similarity of the effect of the LPSO and RE-rich solid solution matrix phases on Qcand high-temperature strength.
基金Project(2020A1515110869)supported by Guangdong Basic and Applied Basic Research Foundation,ChinaProject(GJHZ20190822095418365)supported by Shenzhen International Cooperation Research,China+3 种基金Project(51775351)supported by the National Natural Science Foundation of ChinaProject(2019011)supported by the NTUT-SZU Joint Research Program,ChinaProject(2019040)supported by the Natural Science Foundation of SZU,ChinaProject(ASTRA6-6)supported by the European Regional Development Fund,European Union。
文摘Ti-6Al-4V specimens were fabricated by selective laser melting(SLM)to study the effect of thermal treatment on the phase transformation,elemental diffusion,microstructure,and mechanical properties.The results show that vanadium enriches around the boundary ofαphases with increasing annealing temperature to 973 K,andα′phases transform intoα+βat 973 K.The typicalα′martensite microstructure transforms to fine-scale equiaxed microstructure at 973 K and the equiaxed microstructure significantly coarsens with increasing annealing temperature to 1273 K.The SLM Ti-6Al-4V alloy annealed at 973 K exhibits a well-balanced combination of strength and ductility((1305±25)MPa and(37±3)%,respectively).
基金by the National National Science Foundation of China(Nos.U1862205,51473085,and 21873054)Tsinghua University Initiative Scientific Research Program(No.20194180048)。
文摘The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the extended-chain crystal(ECC)of the same polymer as nucleating agent.The crystallization of PBS with its ECC as nucleating agent in a wide temperature range(90–127°C)and the following melting behavior were studied.It is revealed that the melting point(Tm',for Tc≥113°C)and the annealing peak temperature(Ta',for Tc=90–100°C)show similar asymptotic behavior.Both Tm and Ta approach to a value of ca.3.3°C higher than the corresponding Tc when the crystallization time tc approaches the starting point.That is to say,the Hoffman-Weeks plot is parallel to Tm=Tc line.The crystallization line became parallel to the melting line when PBS was crystallized at Tc higher than 102°C.Based on these results,we propose that the parallel relationship and the intrinsic similarity between the Ta and the Tm observed at the two ends of the Tc range could be attributed to the metastable crystals formed at the beginning of crystallization.
基金US Army Research Office (YW) the Drexel &Hahnemann University Synergy Grant (YW&PIL)+3 种基金 the Commonwealth of Pennsylvania through agrant to the Nanotechnology Institute of Southeastern Pennsylvania (YW PIL &AGM) National Institutes of Health ( DE09848 to YW) and NASA Graduate Student Research Fellowship (NAG9-1380)
