The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive sp...The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive spectroscopy EDS transmission electron microscope TEM electron back-scatter diffraction EBSD and X-ray diffraction XRD . The results show that M2 C is the prevailing type of eutectic carbides in M42 steel. After modification with rare earth metals M2 C eutectic carbides change from the ordered lamellar structure into a circular structure.Despite different morphologies the two carbides present the same characteristics of microstructure and growth orientation.Compared with lamellar carbides M2 C carbides with the circular structure are much easier to decompose and spheroidize after heating which remarkably refines the carbide dimensions.The refined carbides improve the supersaturation of alloying elements in martensite and increase the hardness of M42 steel by 1.5 HRC.展开更多
为改善亚微米级球形RDX的规模化制备技术,以提升其形貌均匀性、热稳定性及安全性,采用超声辅助气动浸渍重结晶(PIR)法制备亚微米球形RDX,通过SEM、XRD对其进行表征,研究了溶剂种类及喷头浸没深度对RDX形貌与粒径的影响,并对其热分解性...为改善亚微米级球形RDX的规模化制备技术,以提升其形貌均匀性、热稳定性及安全性,采用超声辅助气动浸渍重结晶(PIR)法制备亚微米球形RDX,通过SEM、XRD对其进行表征,研究了溶剂种类及喷头浸没深度对RDX形貌与粒径的影响,并对其热分解性能和机械感度进行了测试。结果表明:以二甲基亚砜(DMSO)为溶剂、去离子水为非溶剂、浸没深度为5 mm时,制备的RDX颗粒呈球形,表面光滑,平均粒径为0.675μm,与传统喷雾重结晶法相比,其粒度更小、分布更窄、颗粒更圆润;XRD分析显示,PIR处理未改变RDX的晶型;与原料RDX相比,PIR处理所得RDX的表观活化能提高了53.35 k J·mol^(-1),热爆炸临界温度降低了28.39℃,特性落高(H50)提高了29.9 cm,爆炸概率降低了35%。PIR法能够制备出形貌均匀、热稳定性较高且机械感度较低的亚微米球形RDX。展开更多
For processing parts made from medium carbon steel, toughness and flexibility are of importance. There- fore, to achieve these properties, the cementite in the steels is spheroidized through heat treatment. Different ...For processing parts made from medium carbon steel, toughness and flexibility are of importance. There- fore, to achieve these properties, the cementite in the steels is spheroidized through heat treatment. Different parameters such as the time and temperature of spheroidizing and the initial microstructure of the steel affect the amount of spheroidized cementite. In the present work, the percent of contribution of two parameters, i.e. initial microstructure and spheroidizing time, to the percent of spheroidization in CK60 steel was investigated using Taguchi robust design. The initial microstructures consisted of martensite, coarse pearlite, fine pearlite and bainite and the chosen spheroidization times were 4, 8, 12, and 16h. Spheroidizing was done at the constant temperature 700℃. After spheroidizing was completed, the samples were prepared in order to observe their microstructure under an optical microscope and to determine the spheroidized percent using MIPTM （metallographic image processing） software. It was found that the spheroidizing time had the most influence （58.5 ~//0） on spheroidized percent and the initial microstructure only had a 31.1% contribution. Finally, the instantaneous growth rate of the carbide was also deduced.展开更多
A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The ...A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The UHCS produced by this new process has a microstructure with recrystallized ferrite matrix and fine and uniform carbide particles. After this spheroidizing, the UHCS exhibits good mechanical properties at ambient temperature, for example σb= 1 100 MPa, σs =915 MPa, δ=8% and high ratio of σs/σb.展开更多
The low-strength and high-brittleness of AZ91 cast magnesium alloy mainly result from the coarse divorced eutectic phase. To solve these problems, the annealing treatment of AZ91 cast magnesium alloy was carried out a...The low-strength and high-brittleness of AZ91 cast magnesium alloy mainly result from the coarse divorced eutectic phase. To solve these problems, the annealing treatment of AZ91 cast magnesium alloy was carried out at 415 ℃ and held for 24 h in this study and the alloy was then slowly cooled to room temperature in furnace. The microstructures of the alloy were observed using a metallographic microscope, a transmission electron microscopy and an emission scanning electron microscopy, respectively. The phase analysis was performed using the X-ray diffraction, and the tensile test of the specimen at ambient temperature was performed on a material test machine. The results indicate that the coarse divorced eutectic phase dissolves into the Mg matrix during the isothermal process, and the lamellarβ-Mg17AI12 phase precipitates from the magnesium solid solution with a type of pearlite precipitation during furnace cooling. Consequently, the spheroidizing treatment was carried out at 320℃ for 20 h following the annealing process and the lamellar β-Mg17A12 phase was spheroidized. Compared with the as-cast alloy, the strength and ductility of the AZ91 magnesium alloy are increased obviously after annealing treatment; the yield strength and tensile strength are increased to 137.8 MPa and 240.4 MPa from 102.9 MPa and 199.3 MPa, respectively; and the elongation is improved to 6.12% from 4.35%. After being spheroidized, the strength and hardness decrease a little, but the ductility is elevated to 7.23%. The nucleation, growth and spheroidizing mechanism of the lamellarβ-Mg12TAI12 phase were also discussed.展开更多
基金The National Natural Science Foundation of China(No.51301038,51201031,51371050)the Industry-AcademiaResearch Cooperative Innovation Fund of Jiangsu Province(No.BY2014127-03)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20141306)the Scientific and Technological Innovation Fund of Danyang(No.SY201305)
文摘The influence of rare earth metals and heat treatment on the microstructure and performance of M42 steel has been investigated by means of an optical microscope OM scanning electron microscope SEM energy dispersive spectroscopy EDS transmission electron microscope TEM electron back-scatter diffraction EBSD and X-ray diffraction XRD . The results show that M2 C is the prevailing type of eutectic carbides in M42 steel. After modification with rare earth metals M2 C eutectic carbides change from the ordered lamellar structure into a circular structure.Despite different morphologies the two carbides present the same characteristics of microstructure and growth orientation.Compared with lamellar carbides M2 C carbides with the circular structure are much easier to decompose and spheroidize after heating which remarkably refines the carbide dimensions.The refined carbides improve the supersaturation of alloying elements in martensite and increase the hardness of M42 steel by 1.5 HRC.
文摘为改善亚微米级球形RDX的规模化制备技术,以提升其形貌均匀性、热稳定性及安全性,采用超声辅助气动浸渍重结晶(PIR)法制备亚微米球形RDX,通过SEM、XRD对其进行表征,研究了溶剂种类及喷头浸没深度对RDX形貌与粒径的影响,并对其热分解性能和机械感度进行了测试。结果表明:以二甲基亚砜(DMSO)为溶剂、去离子水为非溶剂、浸没深度为5 mm时,制备的RDX颗粒呈球形,表面光滑,平均粒径为0.675μm,与传统喷雾重结晶法相比,其粒度更小、分布更窄、颗粒更圆润;XRD分析显示,PIR处理未改变RDX的晶型;与原料RDX相比,PIR处理所得RDX的表观活化能提高了53.35 k J·mol^(-1),热爆炸临界温度降低了28.39℃,特性落高(H50)提高了29.9 cm,爆炸概率降低了35%。PIR法能够制备出形貌均匀、热稳定性较高且机械感度较低的亚微米球形RDX。
文摘For processing parts made from medium carbon steel, toughness and flexibility are of importance. There- fore, to achieve these properties, the cementite in the steels is spheroidized through heat treatment. Different parameters such as the time and temperature of spheroidizing and the initial microstructure of the steel affect the amount of spheroidized cementite. In the present work, the percent of contribution of two parameters, i.e. initial microstructure and spheroidizing time, to the percent of spheroidization in CK60 steel was investigated using Taguchi robust design. The initial microstructures consisted of martensite, coarse pearlite, fine pearlite and bainite and the chosen spheroidization times were 4, 8, 12, and 16h. Spheroidizing was done at the constant temperature 700℃. After spheroidizing was completed, the samples were prepared in order to observe their microstructure under an optical microscope and to determine the spheroidized percent using MIPTM （metallographic image processing） software. It was found that the spheroidizing time had the most influence （58.5 ~//0） on spheroidized percent and the initial microstructure only had a 31.1% contribution. Finally, the instantaneous growth rate of the carbide was also deduced.
基金Item Sponsored by Provincial Natural Science Foundation of Hebei Province of China (500023)
文摘A new spheroidizing process of ultra-high carbon steel （UHCS） containing C 1.55%, Cr 1.45%, and Al 1.5% in mass percent has been proposed. The effect of processing parameters on the microstructure was analyzed. The UHCS produced by this new process has a microstructure with recrystallized ferrite matrix and fine and uniform carbide particles. After this spheroidizing, the UHCS exhibits good mechanical properties at ambient temperature, for example σb= 1 100 MPa, σs =915 MPa, δ=8% and high ratio of σs/σb.
基金supported by the National Science&Technology Pillar Program of China(Grant No.2006BAE04B05-1)the Natural Science Foundation of Shanxi Province(Grant No.2012JQ6020)the Doctor Foundation of Xian University of Science & Technology of China(2011QDJ017)
文摘The low-strength and high-brittleness of AZ91 cast magnesium alloy mainly result from the coarse divorced eutectic phase. To solve these problems, the annealing treatment of AZ91 cast magnesium alloy was carried out at 415 ℃ and held for 24 h in this study and the alloy was then slowly cooled to room temperature in furnace. The microstructures of the alloy were observed using a metallographic microscope, a transmission electron microscopy and an emission scanning electron microscopy, respectively. The phase analysis was performed using the X-ray diffraction, and the tensile test of the specimen at ambient temperature was performed on a material test machine. The results indicate that the coarse divorced eutectic phase dissolves into the Mg matrix during the isothermal process, and the lamellarβ-Mg17AI12 phase precipitates from the magnesium solid solution with a type of pearlite precipitation during furnace cooling. Consequently, the spheroidizing treatment was carried out at 320℃ for 20 h following the annealing process and the lamellar β-Mg17A12 phase was spheroidized. Compared with the as-cast alloy, the strength and ductility of the AZ91 magnesium alloy are increased obviously after annealing treatment; the yield strength and tensile strength are increased to 137.8 MPa and 240.4 MPa from 102.9 MPa and 199.3 MPa, respectively; and the elongation is improved to 6.12% from 4.35%. After being spheroidized, the strength and hardness decrease a little, but the ductility is elevated to 7.23%. The nucleation, growth and spheroidizing mechanism of the lamellarβ-Mg12TAI12 phase were also discussed.
