黄林
,
李金柳
,
李国超
,
郝江江
,
胥永刚
材料科学与工程学报
doi:10.14136/j.cnki.issn 1673-2812.2017.02.023
研究了Mn50.35Cu(48.1x)Al1.55Fex合金的阻尼性能的变化规律,借助X射线衍射仪分析了时效态合金的衍射图谱,并利用图解外推法分析计算了合金的晶格常数及Fe原子所引起的晶格畸变,采用光学显微镜观察其金相组织,借助多功能内耗仪分析了合金的阻尼性能及马氏体转变温度.结果表明,Fe元素的加入导致合金晶粒细化;且固溶的Fe原子引起的晶格畸变会增加调幅分解的阻力,阻碍富Mn区的形成,导致马氏体转变温度降低,阻尼性能下降.
关键词:
Mn5o.35CU(48.1-x)Al1.55Fex合金
,
阻尼性能
,
Fe含量
,
晶格畸变
,
马氏体转变
Zhonggang SUN
金属学报(英文版)
The TEM and HRTEM were utilized to investigate the phase transformation of hydrogenated Ti-6Al-4V alloys (0 wtpct-0.9 wt pct H) treated by annealing and quenching from β field. The results indicate that the orthorhombic α'' martensite and β phase appear progressively with the increase of hydrogen concentration. On the other hand, hydrides with sizes of 2-5 nm are observed in the specimens containing more than 0.6 wt pct hydrogen. The formation of α'' and twins can be attributed to the internal stress caused by solid solution of hydrogen and hydrides precipitation.
关键词:
Ti-6Al-4V alloys
,
Martensitic transformation
,
Hydrogenation
,
Hydride
Lie ZHAO
,
Fred J. VERMOLEN
,
Jilt SIETSMA
,
Sybr
,
van der ZWAAG
材料科学技术（英文）
The present work analyses the total free energy of the material during the martensitic transformation. A general expression for the martensite fraction as a function of temperature is derived, assuming that the nonchemical free energy is proportional to the volume of martensite. This expression indicates that the temperature-dependent martensite fraction can be predicted once the characteristic transformation temperatures and the relation between the chemical free energy and temperature of the martensite and austenite are known. An advantage of this development is that the proposed equation is valid for all types of relations between the chemical free energy and temperature. This simulation is successfully applied to the martensitic transformation upon further cooling of retained austenite in a low-alloyed TRIP steel, in which the relation between chemical free energy and temperature is quadratic and the fraction is determined from a thermo-magnetic measurement.
关键词:
Thermodynamics
,
null
,
null
,
null
Zhirong HE
,
Fang WANG
,
Jing'en ZHOU
材料科学技术（英文）
The basic martensitic transformation (MT) properties of Ru50Ta50 alloy, i.e. MT temperature (MTT), temperature hysteresis (ΔT), and MT heat (ΔH) were investigated in this paper. The effects of heat treatment and thermal cycling on MT behavior of Ru50Ta50 alloy, the deformation and microstructure characteristics of Ru50Ta50 alloy were also studied for its engineering application as high temperature actuator/sensor materials by means of differential scanning calorimetry, X-ray diffraction, transmission electron microscope, optical microscope, and hardness test. The results showed that a two-stage reversible MT takes place in Ru50Ta50 alloy. The two-stage MT starting temperatures (MS1 , MS2 ) and the temperature hysteresis (ΔT1, ΔT2) are 1047, 784 and 11, 14℃, respectively. No significant effect of aging treatment and thermal cycling on MTT and ΔT of Ru50Ta50 alloy were observed, but ΔH decreases slowly with increasing thermal cycles. The hardness and brittleness of Ru50Ta50 alloy are high. The deformation mode of RuTa alloys is twinning.
关键词:
RuTa alloy
,
热处理
,
热循环
,
形状记忆合金
,
Ru
Xiaodong WANG
,
Baoxu HUANG
,
Yonghua RONG
,
Li WANG
,
null
,
null
,
null
,
null
材料科学技术（英文）
Transformation induced plasticity (TRIP) steels combine high strength and excellent ductility, making them suited for application in crash-relevant parts in the automotive industry. However, the high Si contents in the conventional TRIP steel will generate surface defects on the hot rolled strip, which is difficult to process in continuous galvanizing lines. In order to solve the above problem the TRIP steel with the addition of Al replacing majority of Si was designed. In the present paper, the volume fraction of various phases in a C-Mn-Si-Al-Cr TRIP steel was determined by metallographic examination and X-ray diffraction analysis, and the multi-phase microstructures were characterized using an atomic force microscope based on their height difference. Tensile tests were performed at different temperatures ranging from -40℃ to 90℃. The results show that transition temperature MSσ in the present TRIP steel cannot be determined due to its lower volume fraction of retained austenite, different from the conventional TRIP steel. While the yield stress and tensile strength at different temperatures are higher than those of the conventional TRIP steel, which is attributed to the addition of Cr. In order to evaluate the effect of martensitic transformation on the total elongation, the sample without retained austenite obtained by quenching in liquid nitrogen was carried out under tensile test. The results indicate that the elongation of the original sample containing 9% retained austenite is about 20% higher than that of the sample quenched in liquid nitrogen, which demonstrates that the retained austenite plays an important role in improving the elongation of the TRIP steel.
关键词:
TRIP steel
,
steel
,
mechanical
,
properties
,
retaine
Yanjun ZHENG
,
Lishan CU
,
IYan LI
,
Dazhi YANG
材料科学技术（英文）
The reverse martensitic transformation of TiNi shape memory alloy fibers embedded in a pure aluminum matrix was studied in this paper. Results showed that the phase composition of the TiNi alloy fibers prior to prestraining at the room temperature had a significant influence on the differential scanning calorimetry (DSC) results of the composites. By a comparison to the high temperature X-ray diffraction (XRD) results, it was confirmed that the martensite was divided into two groups: the self-accommodating martensite (SAM) and the preferentially oriented martensite (POM). The evolving process of the separation of martensite was discussed.
关键词:
Shape memory alloy
,
null
,
null
,
null
