Luhan Hao Namin Xiao Chengwu Zheng Dianzhong Li
材料科学技术（英）
The microstructures and mechanical properties of deformation induced ferrite (DIF) in the low carbon steel Q235 under different deformation temperatures have been investigated systematically. Through deformation induced ferrite transformation (DIFT), ferrite grain can be refined to 3 μm and accounts for above 85% of the overall fraction. Yield strength of DIF (>500 MPa) is increased by up to 100% compared with the conventional low carbon steel. Comparison of microstructure and mechanical properties in the Q235 steel with DIF and tempered DIF microstructure illustrates that the strengthening mechanism of DIF microstructure is the com- bination of grain boundary strengthening and carbon supersaturated strengthening. Electron back-scattered diffraction (EBSD) analysis and high magnification scanning electron microscopy (SEM) observation denote that high-angle grain boundary among ultrafine ferrite grain and the transformation product of retain austenite membrane along ferrite boundaries are responsible for the stability of ferrite grain size during tempering
process. Transmission electron microscopy (TEM) analysis demonstrates that the transformation product of retained austenite membrane between ferrite grain boundaries is cementite.
关键词:
Low carbon steel
,
DIFT
,
Grain size
,
Mechanical properties
,
Temper resistance
Xinli Song Zexi Yuan Juan Jia Di Wang Pinghe Li Zhaojun Deng
材料科学技术（英）
The cold-rolled (75% reduction ratio) Ti-IF (interstitial-free) steels of 1 mm thickness were recrystallized by annealing at 810°C for different times. The microstructure, mechanical properties and phosphorus segregation at grain boundary were investigated by means of optical microscopy (OM), tensile testing and field emission transmission electron microscopy (FE-TEM). It was observed that recrystallization was completed after annealing at 810°C for 180 s. The yield strength and tensile strength decreased as annealing time increased. The FE-TEM observation showed that after the annealing treatment, the grain boundary was broadened and the dislocations with higher density of phosphorus atoms and phosphide at grain boundaries became evident. The amount of phosphorus segregated at grain boundaries increased with annealing time.
关键词:
IF (interstitial-free) steel
,
Segregation
,
Mechanical properties
,
Recrystallization annealing
Xinli Song Zexi Yuan Juan Jia Di Wang Pinghe Li Zhaojun Deng
材料科学技术（英）
The cold-rolled (75% reduction ratio) Ti-IF (interstitial-free) steels of 1 mm thickness were recrystallized by annealing at 810°C for different times. The microstructure, mechanical properties and phosphorus segregation at grain boundary were investigated by means of optical microscopy (OM), tensile testing and field emission transmission electron microscopy (FE-TEM). It was observed that recrystallization was completed after annealing at 810°C for 180 s. The yield strength and tensile strength decreased as annealing time increased. The FE-TEM observation showed that after the annealing treatment, the grain boundary was broadened and the dislocations with higher density of phosphorus atoms and phosphide at grain boundaries became evident. The amount of phosphorus segregated at grain boundaries increased with annealing time.
关键词:
IF (interstitial-free) steel
,
Segregation
,
Mechanical properties
,
Recrystallization annealing
Kun WU
金属学报(英文版)
In this paper, 10 vol. pct SiCp/AZ91 magnesium matrix composite was fabricated by stir casting technology. The ingots were forged at temperatures of 320, 370 and 420 ℃, respectively. XRD, OM and SEM were used to characterize microstructure of the composites. It was shown that the clusters of particles in the as-cast composite were largely eliminated, and that the tensile strength was improved obviously.
关键词:
Magnesium matrix composite
,
Forging
,
Mechanical properties
王唱舟
,
周丽
,
王洋
,
丁昊
材料科学与工程学报
本文运用有限元法模拟了SiC颗粒体积分数和颗粒尺寸对SiCp/Al复合材料弹性模量、屈服强度、延伸率的影响.为了建立与真实显微结构相似的复合材料模型,假定任意尺寸的SiC颗粒随机地分布在SiCp/Al复合材料中.计算结果表明:SiC颗粒体积分数对复合材料的力学性能的影响更加显著.随着体积分数的增加,SiCp/Al复合材料的弹性模量和屈服强度逐渐增加;而其延伸率会相应降低.其应力应变曲线由韧性材料的特性向脆性材料的特性逐渐过渡.相反,当平均颗粒尺寸在一定的范围内变化时,颗粒尺寸对其应力-应变曲线的影响并不显著.
关键词:
SiCp/Al复合材料
,
体积分数
,
颗粒尺寸
,
力学性能
,
有限元
姜雁斌
,
官磊
,
莫永达
材料热处理学报
研究了电脉冲连续退火对冷轧时效态AZ91镁合金带材显微组织和力学性能的影响.结果表明:电脉冲退火在较低的温度下快速完成了α-Mg基体的再结晶,可显著细化晶粒.当退火温度为210℃时,α-Mg基体发生完全再结晶,其平均晶粒尺寸由冷轧态的约30μm减小为约7μm,带材的抗拉强度由冷轧态的410 MPa减小至334 MPa,断后伸长率由冷轧态的3.7％增大至23％.电脉冲退火后带材的拉伸断裂方式由冷轧态的脆性沿晶断裂转变为韧性穿晶断裂.电脉冲在其热效应和非热效应的共同作用下快速完成再结晶过程以及β-Mg17Al12相阻碍α-Mg基体晶粒长大,是电脉冲退火细化晶粒的主要原因.
关键词:
镁合金
,
电脉冲退火
,
再结晶
,
力学性能
Chunjuan Cui Jun Zhang Lin Liu Hengzhi Fu
材料科学技术（英）
The Si-TaSi2 eutectic in situ composite, which has highly-aligned and uniformly-distributed TaSi2 fibers in the Si matrix, can be obtained when the solidification rate changes from 0.3 to 9.0 mm/min. It is very interesting that one or two TaSi2 fibers are curved when the solidification rate reaches 6.0 mm/min, although it is very brittle in general. The formation mechanism of the curved fiber is discussed and mechanical properties of the TaSi2 fibers are examined by nanoindentation. It is found that the hardness and the elastic modulus of the bended TaSi2 fiber are much higher than that of the straight TaSi2 fiber. Moreover, the reasons why the mechanical properties of the straight TaSi2 fiber are different from that of the curved TaSi2 fiber are discussed. This can be ascribed to internal stress which results from mismatch of the thermal expansion coefficients of the two phases and di®erent crystallographic orientations.
关键词:
Si-TaSi2 eutectic in situ composite
,
null
,
null
,
null
Zhenjun Hong Jingchao Chen Jing Feng Yeping Du Jie Yu Lijuan Zhang Shuzhen Wu Futai Xu
材料科学技术（英）
The mechanical properties of nano-scale Cu/FeS composite were simulated by molecular dynamics (MD) simulation in this paper. Through the analysis on the stress-strain curves, the results of MD simulation were in good agreement with mechanisms of macroscopic deformation. When the size of particles was smaller than a certain value, the relationship between yield strength and size, which was different from the large size crystals abided by the contrary Hall-Petch relationship. Based on the discussion of nano-scale Cu/FeS composite, some interesting conclusions were obtained. For example, the "S" type curves were discovered in stress-strain curves and the anisotropy of FeS was very evident when the exposures of reinforcing phase (FeS) were different and so on. The basic theories and calculations of the composite that contains nano-scale particles were discussed. At the same time, a new modeling building method of composites, which was close to actual experiences, were considered in this paper.
关键词:
Nano-scale composite
,
mechanical properties
,
molecular dynamics simulation
,
elastic modulus
,
strain rigidity
Weiguo Jiang
材料科学技术（英）
A novel water-soluble core material composed of polyethylene glycol, sodium chloride, mica powder and plasticizer was prepared. The compressive strength, bend strength, hygroscopic coefficient and the material solubility in water were investigated. The results show that the compressive yield strength of the soluble core can reach 1 MPa and the highest compressive strength can reach 4 MPa, the bend strength is as high as 6.65 MPa, the hygroscopic coefficient is lower than 0.22%/month and the solubility of suitable core material is 35.7-55.75 g/(min·m2). The wax pattern with undercuts was prepared successfully by using the novel water-soluble core material.
关键词:
Investment cast
,
Core materials
,
Mechanical property
,
Microstructure
Zhuang Li Di Wu
材料科学技术（英）
The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe. The experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels. The conventional austenitic stainless steel 1Cr18Ni9Ti (steel A) and the free cutting austenitic stainless steel (steel B) were prepared. The results have shown that machinable inclusions were composed of MnS and CuO, and they might be also Ti4C2S2. The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis (EPMA), which might be one of the most important factors to improve the machinability of austenitic stainless steels. The cutting forces for steel B were lower than those of steel A at various cutting speeds; the abrasion depth of theflank of the tool for steel B was less than that of the steel A under the same cutting conditions. The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives, such as S, Cu and Bi. Ultimate tensile, yield strength, and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.
关键词:
Austenitic stainless steel
,
free-cutting additives
,
bismuth
,
machining characteristics
,
the mechanical properties.
