In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in diffe...In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in different states,especially after hot extrution and solid solution treatment,was systematically studied using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and mechanical tests at room temperature.The results show that 0.2wt.% Mn can both refine the as-cast microstructure of the alloy and strengthen the extrusion+T6 state alloy without damaging the plasticity badly due to the formation of Al 15(FeMn) 3 Si 2 and Al 15 Mn 3 Si 2 dispersoids.Compared with the extrusion+T6 state alloy without Mn addition,the ultimate tensile strength and yield strength of the alloy with 0.2wt.% Mn addition are increased from 416.9 MPa to 431.4 MPa,360.8 MPa to 372 MPa,respectively.The elongation of the extrusion+T6 state alloy does not show obvious change when the Mn addition is less than 0.5wt.%,and for the alloy with 0.2wt.% Mn addition its elongation is still as high as 15.6%.However,when over 0.7wt.% Mn is added to the alloy,some coarse,stable and refractory AlVMn and Al(VMn)Si phases form.These coarse phases can reduce the effect of Mn on the inhibition of re-crystallization;and they retain the angular morphology permanently after the subsequent deformation process and heat treatment.This damages the mechanical properties of the alloy.展开更多
The effects of prestrain and annealing temperature on phase transformation temperatures in Fel4Mn5Si8Cr4Ni shape memory alloy have been studied. The results showed that when the annealing temperature was 673 K, both t...The effects of prestrain and annealing temperature on phase transformation temperatures in Fel4Mn5Si8Cr4Ni shape memory alloy have been studied. The results showed that when the annealing temperature was 673 K, both the At and the Ms temperatures increased appreciably as the prestrain increased, the As temperature increased slightly with increasing prestrain; the resistivity difference at 303 K between the heating and cooling curve also increased with increasing prestrain, which agreed with the recovery strain. The shape memory effect in Fe-Mn-Si-Cr-Ni shape memory alloy is caused by the stress-induced γ→ε martensite transformation and its reverse transformation. When the prestrain was 10%, the Ms temperature decreased remarkably as the annealing temperature increased.展开更多
The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles r...The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.展开更多
The changes of tempering microstructure and properties of Fe-Cr-V-Ni-Mn-C cast alloys with martensite matrix and much retained austenite are studied. The results showed that when tempering at 200 °C the amount of...The changes of tempering microstructure and properties of Fe-Cr-V-Ni-Mn-C cast alloys with martensite matrix and much retained austenite are studied. The results showed that when tempering at 200 °C the amount of retained austenite in the alloys is so much that is nearly to as-cast, and a lot of retained austenite decomposes when tempering at 350°C and the retained austenite decomposes almost until tempering at 560 °C. When tempering at 600 °C, the retained austenite in the alloys all decomposes. At 560°C the hardness is highest due to secondary hardening. The effect of nickel and manganese on the microstructure and properties of Fe-Cr-V-C cast alloy were also studied. The results show that the Fe-Cr-V-C cast alloy added nickel and manganese can obtain martensite matrix and much retained austenite microstructure, and nickel can also prevent pearlite transformation. With the increasing content of nickel and manganese, the hardness of as-cast alloy will decreases gradually, so one can improve the hardness of alloy by tempering process. When the content of nickel and manganese is 1.3-1.7%, the hardness of secondary hardening is the highest (HRC64). But when the content of nickel and manganese increase continually, the hardness of secondary hardening is low slightly, and the tempering temperature of secondary hardening rises.展开更多
Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150℃ and t...Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150℃ and the strain rate range was 0.01–5 s^(-1)on a Gleeble-3800 thermal simulator machine. The results showed that the flow stress increased with decreasing deformation temperature and increasing strain rate. According to the constitutive equation, the activation energy of hot deformation was 422.88 kJ·mol^(-1). The relationship between the critical stress and peak stress of the tested steel was established, and a dynamic recrystallization kinetic model was thus obtained. Based on this model, the effects of strain rate and deformation temperature on the volume fraction of dynamically recrystallized grains were explored. The microstructural examination and processing map results revealed that the tested steel exhibited a good hot workability at deformation temperatures of 1010–1100℃ and strain rate of 0.01 s^(-1).展开更多
汽车行业的迅速发展使得能源消耗、环境污染等问题日益严重,而开发高强度且轻量化的汽车用钢对节能减排具有重要意义。目前正在研发的第三代先进高强钢包括轻质(Lightweight)钢、Q&P(Quenching and partitioning)钢和中锰钢(Mn质量...汽车行业的迅速发展使得能源消耗、环境污染等问题日益严重,而开发高强度且轻量化的汽车用钢对节能减排具有重要意义。目前正在研发的第三代先进高强钢包括轻质(Lightweight)钢、Q&P(Quenching and partitioning)钢和中锰钢(Mn质量分数为5%~10%)。其中,Fe-Mn-Al-C系低密度高强钢由于Al元素的加入,在密度降低的同时保持着良好的力学性能,满足第三代汽车用钢对轻量化的要求。同时,由于大量Al、Mn和C元素的添加,Fe-Mn-Al-C系低密度钢的冶炼连铸、微观结构、变形机制、加工过程及应用性能与传统钢种大不相同。本文系统阐述了Fe-Mn-Al-C系低密度钢的成分设计及其中合金元素的作用,介绍了低密度钢的微观组织结构特征;重点讨论了单一铁素体钢、奥氏体基钢、奥氏体基双相钢和铁素体基双相钢的各种强韧化机制,包括固溶强化、细晶强化、沉淀强化及其独特的应变硬化机制,如相变诱导塑性(TRIP)、孪晶诱导塑性(TWIP)、微带诱导塑性(MBIP)、剪切带诱导塑性(SIP)和动态滑移带细化(DSBR)等;并就层错能(SFE)对奥氏体钢变形机制产生的影响进行了总结;最后,对Fe-Mn-Al-C系低密度钢的强韧化机制研究进行展望,为后续研究者的工作提供参考。展开更多
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2020CDJDPT001)the Chongqing Natural Science Foundation,China(No.cstc2021jcyj-msxm X0699)。
基金financially supported by the Fundamental Research Funds for Central Universities of China(Grant Nos.N110609002and N110408005)
文摘In order to improve the performances of the Al-Mg-Si-Cu-Cr-V alloy,various amounts of Mn(0-0.9wt.%) were added.The effect of this Mn on the microstructures and mechanical properties of Al-Mg-Si-Cu-Cr-V alloys in different states,especially after hot extrution and solid solution treatment,was systematically studied using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and mechanical tests at room temperature.The results show that 0.2wt.% Mn can both refine the as-cast microstructure of the alloy and strengthen the extrusion+T6 state alloy without damaging the plasticity badly due to the formation of Al 15(FeMn) 3 Si 2 and Al 15 Mn 3 Si 2 dispersoids.Compared with the extrusion+T6 state alloy without Mn addition,the ultimate tensile strength and yield strength of the alloy with 0.2wt.% Mn addition are increased from 416.9 MPa to 431.4 MPa,360.8 MPa to 372 MPa,respectively.The elongation of the extrusion+T6 state alloy does not show obvious change when the Mn addition is less than 0.5wt.%,and for the alloy with 0.2wt.% Mn addition its elongation is still as high as 15.6%.However,when over 0.7wt.% Mn is added to the alloy,some coarse,stable and refractory AlVMn and Al(VMn)Si phases form.These coarse phases can reduce the effect of Mn on the inhibition of re-crystallization;and they retain the angular morphology permanently after the subsequent deformation process and heat treatment.This damages the mechanical properties of the alloy.
文摘The effects of prestrain and annealing temperature on phase transformation temperatures in Fel4Mn5Si8Cr4Ni shape memory alloy have been studied. The results showed that when the annealing temperature was 673 K, both the At and the Ms temperatures increased appreciably as the prestrain increased, the As temperature increased slightly with increasing prestrain; the resistivity difference at 303 K between the heating and cooling curve also increased with increasing prestrain, which agreed with the recovery strain. The shape memory effect in Fe-Mn-Si-Cr-Ni shape memory alloy is caused by the stress-induced γ→ε martensite transformation and its reverse transformation. When the prestrain was 10%, the Ms temperature decreased remarkably as the annealing temperature increased.
文摘The effects of aging temperature on shape memory effect, mechanical properties and microstruc-ture of Fe-14Mn-5Si-8Cr-4Ni-0.2C shape memory alloy have been studied. The results showed that the second phase particles rich in chromium, manganese and silicon precipitate during aging, and thereby increase the hardness and strength of the alloy. The shape recovery ratio can be remarkably improved by aging and a maximum value can be obtained at 1223 K, which is 68% higher than that of the specimen in solid solution state. When the aging temperature is below 1223 K, the amount of second phase particles increases as the aging temperature increases. The size of austenite grain increases with increasing aging temperature. When the temperature is over 1223 K, the second phase particles can not precipitate. The lack of second phase particles and the increase of grain size make the hardness and shape recovery ratio drastically decrease, when the temperature is over 1223 K.
文摘The changes of tempering microstructure and properties of Fe-Cr-V-Ni-Mn-C cast alloys with martensite matrix and much retained austenite are studied. The results showed that when tempering at 200 °C the amount of retained austenite in the alloys is so much that is nearly to as-cast, and a lot of retained austenite decomposes when tempering at 350°C and the retained austenite decomposes almost until tempering at 560 °C. When tempering at 600 °C, the retained austenite in the alloys all decomposes. At 560°C the hardness is highest due to secondary hardening. The effect of nickel and manganese on the microstructure and properties of Fe-Cr-V-C cast alloy were also studied. The results show that the Fe-Cr-V-C cast alloy added nickel and manganese can obtain martensite matrix and much retained austenite microstructure, and nickel can also prevent pearlite transformation. With the increasing content of nickel and manganese, the hardness of as-cast alloy will decreases gradually, so one can improve the hardness of alloy by tempering process. When the content of nickel and manganese is 1.3-1.7%, the hardness of secondary hardening is the highest (HRC64). But when the content of nickel and manganese increase continually, the hardness of secondary hardening is low slightly, and the tempering temperature of secondary hardening rises.
基金financially supported by the National Natural Science Foundation of China (Nos. 52071300 and 51904278)the Special Funding Projects for Local Science and Technology Development guided by the Central Committee (No. YDZX20191400004587)+1 种基金the Key Research and Development Project of Zhejiang Province, China (No.2020C01131)the Innovation projects of colleges and universities in Shanxi Province, China (No. 2019L0577)。
文摘Hot compression tests were performed to investigate the hot deformation behavior of Fe–27.34Mn–8.63Al–1.03C lightweight steel and optimize the hot workability parameters. The temperature range was 900–1150℃ and the strain rate range was 0.01–5 s^(-1)on a Gleeble-3800 thermal simulator machine. The results showed that the flow stress increased with decreasing deformation temperature and increasing strain rate. According to the constitutive equation, the activation energy of hot deformation was 422.88 kJ·mol^(-1). The relationship between the critical stress and peak stress of the tested steel was established, and a dynamic recrystallization kinetic model was thus obtained. Based on this model, the effects of strain rate and deformation temperature on the volume fraction of dynamically recrystallized grains were explored. The microstructural examination and processing map results revealed that the tested steel exhibited a good hot workability at deformation temperatures of 1010–1100℃ and strain rate of 0.01 s^(-1).
文摘汽车行业的迅速发展使得能源消耗、环境污染等问题日益严重,而开发高强度且轻量化的汽车用钢对节能减排具有重要意义。目前正在研发的第三代先进高强钢包括轻质(Lightweight)钢、Q&P(Quenching and partitioning)钢和中锰钢(Mn质量分数为5%~10%)。其中,Fe-Mn-Al-C系低密度高强钢由于Al元素的加入,在密度降低的同时保持着良好的力学性能,满足第三代汽车用钢对轻量化的要求。同时,由于大量Al、Mn和C元素的添加,Fe-Mn-Al-C系低密度钢的冶炼连铸、微观结构、变形机制、加工过程及应用性能与传统钢种大不相同。本文系统阐述了Fe-Mn-Al-C系低密度钢的成分设计及其中合金元素的作用,介绍了低密度钢的微观组织结构特征;重点讨论了单一铁素体钢、奥氏体基钢、奥氏体基双相钢和铁素体基双相钢的各种强韧化机制,包括固溶强化、细晶强化、沉淀强化及其独特的应变硬化机制,如相变诱导塑性(TRIP)、孪晶诱导塑性(TWIP)、微带诱导塑性(MBIP)、剪切带诱导塑性(SIP)和动态滑移带细化(DSBR)等;并就层错能(SFE)对奥氏体钢变形机制产生的影响进行了总结;最后,对Fe-Mn-Al-C系低密度钢的强韧化机制研究进行展望,为后续研究者的工作提供参考。
