共查询到19条相似文献,搜索用时 46 毫秒
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研究了Fe含量对Ni56Mn25-xFexGa19(x=0~10)合金的微观组织结构、相变行为、力学性能和记忆特性的影响规律.当x ≤ 4时,Ni56Mn25-xFexGa19合金仍然保持着单一的四方结构马氏体相;当x ≥ 6时,合金呈现为马氏体相和面心立方γ相组成的双相结构.相对于马氏体相,γ相为富Ni和富Fe相,其含量随Fe含量的增加而增加.随着Fe含量增加,合金的马氏体相变温度逐渐降低,其峰值温度从x=0时的356℃降低至x=10时的170℃,这主要归因于马氏体相尺寸因素和电子浓度的综合作用.通过添加Fe替代Mn在合金中引入的γ相可提高合金的强度和塑性,但最大形状记忆回复应变从x=0时的5.0%降低到x=6时的2.0%. 相似文献
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采用差示扫描量热分析(DSC)、光学显微镜、X射线衍射分析(XRD)、扫描电子显微分析(SEM)、压缩试验和物性测量系统(PPMS),系统研究了Ni50-xCoxMn41Sn9(x=0,1,3,5,7,9,10,12,14)合金的马氏体相变、微观结构、相组成、力学性能和磁性能。结果表明,Co含量≥10%时,Ni50-xCoxMn41Sn9合金中析出多呈枝节状的第二相。第二相为富Co贫Sn相,属于面心立方结构,多在晶界上析出,其体积分数随Co含量的增加而增多,热处理不能消除第二相。Co的加入不改变合金的相变顺序,即所有成分合金均发生一步马氏体相变和逆相变,但会导致相变温度下降,当Co含量由0增加到10%(原子分数),马氏体相变开始温度(Ms)从196.9℃降低到144.8℃,这是因为Co取代Ni使得合金基体的价电子浓度下降导致的。Co加入NiMnSn后,提高了合金的力学性能,特别是当合金中存在第二相时,合金的断裂强度和断裂应变量呈现跳跃性增长,两者分别提高了600 MPa和7%,主要原因是晶粒细化。磁学测试结果表明,随着Co含量的增加,合金磁性有所增强,室温下Co含量为12%的合金表现出典型的铁磁性特征,饱和磁化强度高达118 A·m2·kg-1。 相似文献
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徐祖耀 《有色金属材料与工程》1989,(2)
根据作者的工作、并结合新近文献,对近等原子Ni-Ti合金中的相变作了系统的综述,包括:相变的顺序,无公度相变,R相变,马氏体相变,合金成分及热循环对相变临界温度的影响,逆相变及沉淀。 相似文献
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本文通过添加Sn元素来取代Ga元素,制备了Ni57Mn25Ga18-xSnx(x=0,1,2,4)系列形状记忆合金,研究Sn合金化对Ni-Mn-Ga高温形状记忆合金微观组织和马氏体相变的影响。结果表明:Ni57Mn25Ga18-xSnx(x=0,1,2,4)合金基体为单一非调制四方结构的板条状马氏体相,随Sn含量的增加,无新相析出,马氏体板条变宽大,晶粒尺寸增大,马氏体相变的转变温度和逆转变温度均下降,相变滞后增大。 相似文献
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Ferromagnetic shape memory alloys (FSMAs) such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% - 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature (To) higher than 100℃. In this work, the effects of substitution of Co for Ni on the martensitic and magnetic transformations, crystal structures and phase equilibria in Ni-Ca-Fe alloys were studied. Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere. Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy (El)X). The martensitic transformation temperatures and Tc were measured by differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter (XRD) and transmission electron microscope (TEM). The Curie temperature Tc was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni(54-x) Ga27 Fe19 Cox, Tc increases from 303 K to 408 K with increasing CO content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented. 相似文献
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设计了两种不同的拉拔工艺(减面率/%:工艺一:34.45,31.67,19.00,20.08;工艺二:20.10,19.28,34.64,31.41),研究了道次减面率配置对304H不锈钢丝拉拔过程中马氏体相变、磁性能及力学性能的影响。结果表明:当钢丝总应变量相同时,大减面率配置在前更有利于马氏体转变,其饱和磁化强度更大,反之则马氏体转变量较少,饱和磁化强度较小。钢丝的强度与拉拔真应变呈线性相关,其大小只与拉拔总应变量相关。本试验中,前两个道次减面率为20.10%和19.28%,后两个道次减面率为34.64%和31.41%时,马氏体转变量较少,钢丝的饱和磁化强度较低。 相似文献
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钛合金的马氏体相变 总被引:13,自引:0,他引:13
邓安华 《有色金属材料与工程》1999,20(4):193-199
本文简要阐述了钛合金马氏体相变的原理、特点和应用, 并对钛合金热处理工艺作了叙述。 相似文献
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The phase transformation behaviors of two kinds of magnetic shape memory alloys NisoMn25 x Ga25-x and Ni50 Mn29Ga21-x Tbx were studied. When the composition of Ni in these alloys was constant, increasing Mn and reducing Ga contents make martensitic transformation temperatures rise obviously. Simultaneously, thermal hysteresis of phase transformation reduce but Curie temperature una|ters. When terbium was added, phase transformation temperature went up further and Curie temperature kept constant. The alloys still show strong ferromagnetism and properties of thermoelastic martensite phase transformation. 相似文献
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W. Ito Y. Imano R. Kainuma Y. Sutou K. Oikawa K. Ishida 《Metallurgical and Materials Transactions A》2007,38(4):759-766
Martensitic and magnetic transformation behaviors of Ni50MnIn, Ni45Co5MnIn, and Ni42.5Co7.5MnIn Heusler alloys were investigated by differential scanning calorimetry (DSC), vibrating sample magnetometry (VSM), and
transmission electron microscopy (TEM). The martensitic transformation starting temperature (M
s
) decreases with increasing In composition, while the Curie temperatures (T
c
) of the parent phase are almost independent in each alloy series. On the other hand, the addition of Co resulted in a decrease
of the M
s
and an increase of the T
c
, and the degree of the decline of M
s
was accelerated by magnetic transformation of the parent phase. The M
s
temperature change induced by the magnetic field was also confirmed. It was found that the degree of M
s
change is strongly related to the entropy change by the martensitic transformation, which shows a correlation with T
c
-M
s
. These behaviors can be qualitatively explained on the basis of thermodynamic considerations.
This article is based on a presentation made in the symposium entitled “Phase Transformations in Magnetic Materials,” which
occurred during the TMS Annual Meeting, March 12–16, 2006, in San Antonio, Texas, under the auspices of the Joint TMS-MPMD
and ASMI-MSCTS Phase Transformations Committee. 相似文献
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Stress-Induced Martensitic Transformation Cycling and Two-Way Shape Memory Training in Cu-Zn-Al Alloys 总被引:2,自引:0,他引:2
The character and mechanism of two-way shape memory in Cu-Zn-Al alloys is investigated by means of closely controlled thermomechanical
cycling and careful measurement of the progressive effect of the particular “training” routine, as well as by correlary studies
of submicrostructural evolution as training proceeds. The results establish the quantitative relationship between the cyclic
training routine and the ability of the sample to exhibit two-way shape memory. The variation of numerous training parameters
with cycling is presented and interpreted. Microscopic studies indicate that as two-way shape memory training proceeds, specific
physical features develop in the parent phase submicrostructure, particularly dislocation tangles and “vestigial” martensite
markings; these assist in the nucleation and growth of a preferred martensite plate arrangement during cooling. 相似文献
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Fu-Cheng Yen Kuen-Shyang Hwang Shyi-Kaan Wu Shiau-Han Wu 《Metallurgical and Materials Transactions A》2011,42(8):2431-2441
This study demonstrates that a high density and a high transformation heat can be attained for PM TiNi. With the use of fine
elemental powders, a composition of Ti51Ni49, two-step heating, and persistent liquid-phase sintering at 1553 K (1280 °C), a 95.3 pct sintered density was attained for
compacts with a green density of 66 pct. A transformation heat, ΔH, of 31.9 J/g was also achieved, which is much higher than reported previously for sintered TiNi and is approaching the highest
ΔH reported to date, 35 J/g, for wrought TiNi with low C, O, and N contents. The main reason for having these properties in
powder metal TiNi with higher amounts of C, O, and N is that the extra Ti, that over the equiatomic portion in the Ti-rich
Ti51Ni49, forms Ti2Ni compound, which traps most of the C, O, and N. This results in low interstitial contents and a high Ti/Ni ratio of 50.5/49.5
in the TiNi matrix. The tensile strength, elongation, and shape recovery rate after five training cycles were 638 MPa, 14.6,
and 99.1 pct, respectively, despite the presence of Ti2Ni compounds at grain boundaries. 相似文献
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X. Yang B. N. Qian H. B. Peng B. J. Wu Y. H. Wen 《Metallurgical and Materials Transactions A》2018,49(4):1044-1052
To clarify the effect of W contents on the shape memory effect (SME) in the Co-Al alloys and its influencing mechanism, the SME, martensitic transformation, and deformation behavior were studied in the Co-7Al-xW (x = 0, 4, 6, 9 wt pct) alloys. The results showed that the additions of W all deteriorated the SME in Co-7Al alloy when deformed at room temperature. However, when deformed in liquid nitrogen, the SME in Co-7Al alloy could be remarkably improved from 43 to 78 pct after the addition of 4 pct W, above which the SME decreased rapidly with the increase of W content although the yield strength of the parent phase rose due to the solution strengthening of W. The deterioration in SME induced by the excessive addition of W could be ascribed to its resulting significant drop of the start temperature of martensitic transformation. 相似文献
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The effects of small amount additions of Sm on the martensitic transition and magnetic phase transition of polycrystalline Ni-Mn-Ga alloys were investigated. The experimental results show that the Sm doped alloys also undergo a thermal-elastic martensitic transformation and reverse transformation during cooling and heating process and the addition of Sm decreases the martensitic transformation temperature and Curie temperature in different degree respectively. Ni-Mn-Ga alloys of adding Sm still possess Heusler structure, but their crystal lattice parameters are modified slightly. The addition of a proper amount of Sm does not basically decrease Tc of the alloy when avoiding the appearance of second phase. In addition, the doped alloys have favorable toughness because of grain refinement of Sm. 相似文献