R.Darolia(GE Aircraft Engines
,
1 Neumann Way
,
Cincinnati
,
OH 45215
,
USA)
材料科学技术（英文）
Alloys based on NiAl offer significant payoffs as structural materials in gas turbine applications due to a unique range of physical and mechanical properties These properties include high melting temperature. low density. high thermal conductivity. and excellent environmental resistance Very significant improvements in the strength and ductility of NiAl single crystals have been achieved through alloying. Tensile strength and stress rupture properties which compete with current Ni-base Superalloys have been achieved through precipitation of an ordered L21 Heusler phase in NiAl single crystals Room temperature tensile ductility as high as 6% has been produced in NiAl single crystals containing less than 0.5% (atomic) of Fe. Ga or Mo. However. a single alloy with both room temperature ductility and sufficient high temperature strength has not yet been developed. While activity to develop on alloy with both high temperature strength and room temperature ductility continues. the Current approach also emphasizes design and test methodologies which can accept a material with limited ductility and damage tolerance More work is required on measuring and understanding strain rate sensitivity and impact behaviour While several significant challenges still remain. excellent progress has been made in many areas, and the prognosis for using NiAl alloys as high temperature structural materials is promising
关键词:
R.Darolia (GE Aircraft Engines
,
1 Neumann Way
,
Cincinnati
,
Ohio 45215)
金属学报(英文版)
NiAl alloys offer significant payoffs as structural materials in gas turbine applications due to high melting temperature low density,high thermal conductivity and excellent environmental resistance.Significant improvements in the material properties and processing have been achieved. The current approach also emphasizes design and test methodologies which can accept a material with limited ductility and damage tolerance. NiAl alloys have been successfully manufactured into a variety of turbine components. A high pressure turbine vane is currently being engine tested.
关键词:
: nickel aluminide; NiAl; single crystal; strength;ductility; toughness
王浩
,
刘国权
金属学报
由晶粒长大过程的曲率驱动本质出发, 以不同于MacPherson和Srolovitz的方法, 推导出凸型多面体晶粒的三维von Neumann关系式, 无任何其他形状假设及晶粒尺寸分布或拓扑分布要求. 在应用于凸型多面体晶粒时, 本文结果与MacPherson和Srolovitz给出的结果完全一致. 对于凸型多面体晶粒, 三维个体晶粒长大速率是晶粒平均切直径和晶粒棱总长度的函数, 符合Kinderlehrer指出的$n$维体积的变化速率仅与胞的(n-2)维特征量有关的规律.
关键词:
三维晶粒长大
,
von Neumann relation
,
curvature
,
mean caliper diameter
M Liu
,
XM Zhang
,
M.Z. Liu
,
X.M. Mengand Y Y Li(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)(Metal Material Department
,
Sichuan Union University
,
Chengdu 610065
,
China)
金属学报(英文版)
In this paper by means of TEM and HREM, we found that the presence of r-phase plays the most important role in enabling two way shape memory effect (TWME) to be obtained by the stabilization of stress induced martensite variants (SSIM). This idea is different from the traditional suggestion that strain fields developed by dislocation produced TWME. With prolonged isothermal ageing time, the bainitic tronsforma-tion product α1 precipitated, the amount of γ-phase increased, while the martensite was retained and became less ondered. These factors all reduced TWME. During age-ing, the stacking faults in bainitic product α1 disappeared, which indicated that the bainitic product α1 is a sub-equilibrium phase. The interfaces of α-plates also lost straightness step by step, some plates twisted, bronched and overlapped. Its formation is irreversible in tnorphology and reduces the quantities of martensite. Although the precipitation of r may stabilize some martensite or oppose its growth,α may hinder nucleation of martensite. Thus, it was considered that α-plates were the worst de- stroyed element. These suggestions agreed well with our performance test results in that the transformation temperntures and the amount of TWME changed in the same way with prolonged ageing, firstly increasing and then decreasing after reaching an optimal maximum value.
关键词:
precipitate
,
null
,
null
,
null
Chimei MO Zaitao LI Dept.of Materials Science and Engineering
,
University of Science and Technology of China
,
Hefei 230026
,
ChinaZhengang ZHU Institute of Solid State Physics
,
Academia Sinica
,
Hefei
,
230031
,
China
材料科学技术（英文）
Effect of solution treatment temperature on transformations and two way memory, effect in a Ti- 55.2 wt-%Ni alloy was investigated. The results show that with increasing the solution treatment temperature (T_s), two way memory effect (TWME) decreases continuously and temperatures of martensite and reverse, martensite transformations (MR) rise, but the temperature of R start trans- formation (parent→R) does not change. The results of the internal friction measurements indicate that when T_s=1073 K, internal friction peaks of MR and P→R transformations are larger than those of the specimens after solution-treatments at 973 and 1173 K. With increasing T_s, the de- crease of TWME can be attributed to that the defect stress field caused by the rolling fades out grad- ually and preferential martensite variants, which fit into the defect stress field, decrease. The changes of transformation temperatures and internal friction peaks with T_s are closely related to the change of defect numbers.
关键词:
solution-treatment temperature
,
null
,
null
,
null
LUO Laizhong ZHANG Jinxiu LIN Guangming Zhongshan University
,
Guangzhou
,
510275
,
China Lecturer
,
Dept.of Physics and Institute of Material Science
,
Zhongshan University
,
Guangzhou
,
510275
,
China
金属学报(英文版)
The snap-action behavior of a Ni-Ti alloy disc which is controlled by combination of a nonlinear stress field and temperature has been studied.After treatment for two-way shape memory,all shape memory strain of snap-action finishes abruptly at a certain temperature within an interval of less than 1 ms.The results of resistance measurement and in-situ X-ray diffraction indicate that the snap-action strain is mainly resulted from the snap-action β (?)R transformation.
关键词:
shape memory alloy
,
null
,
null
LIN Guangming HUANG Yuanshi ZHANG Jinxiu Zhongshan University
,
Guangzhou
,
China LIN Guangming
,
Associate Professor
,
Dept.of Physics
,
Zhongshan University
,
Guangzhou 510275
,
China
金属学报(英文版)
The snap-acting transition and two way shape memory (TWSM) effect have been obtained in a TWSM spring made of Ni51Ti49 alloy using the constrained effect of stress on driving force of TWSM material.When the snap-acting transition has been realized:M_s= M_f and A_s=A_f;hysteresis is rectangular,the height (TWSM effect) and width (hysteresis) of the rectangle can be readjusted by means of constrained stress.The results of resistance measurments show that,the snap-acting TWSM effect mentioned above was supplied mainly from the transformation of P←→R.The thermodynamic model has also been proposed to ac- count for the snap-acting transformation.
关键词:
transformation thermodynamics
,
null
,
null
,
null
LIN Guangming CHENXingyuan ZHANG Jinxiu Material Science Research Institute
,
Zhongshan University
,
Guangzhou
,
China WANG Yurui Metallurgy Research Institute of Beijing Iron and Steel Company
,
Beijing
,
China LIN Guangming Associate Professor
,
Department of Physics
,
Zhongshan University
,
Guangzhou 510275
,
China
金属学报(英文版)
Snap-acting two way shape memory device can be obtained by using the design proposed by authors.Some essential parameters which characterize the properties of device have been pro- posed also in this paper.And the principle and method according to which a practical snap-acting device can be designed have been described.
关键词:
shape memory alloy
,
null
,
null
Liming WANG
,
Yufeng ZHENG
,
Wei CAI
,
Xianglong MENG
,
Liancheng ZHAO
材料科学技术（英文）
The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at, pet Ni alloy. It is shown that M-s, and M-f temperature increase with increasing the number of cycles, while A(s) and A(f) temperature decrease during thermal cycling. The total strain at and permanent strain epsilon (p) increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.
关键词:
材料科学技术（英文）
Two near a titanium alloys, Ti-5.6Al-4.8Sn-.0Zr-1Mo-0.35Si (1#) and Ti-6.0Al-4.8Sn-2.0Zr-1Mo-0.35Si (2#), were solution-treated in the upper alpha+beta phase fields, and the duplex mixture microstructures consisting of the less volume fraction primary a phase (alpha(p)) and the transformed beta phase (beta(t)) were obtained. The aging treatments were carried out at 700 degrees C for 1# alloy and 760 degrees C for 2# alloy under varied terms, respectively. It guaranteed alpha(2) ordered phase to precipitated only in ap but not in beta(t) for the two alloys. The slower precipitation and growth of the a2 ordered phase and silicide was observed in 1# alloy in comparison with 2# alloy. The mechanical properties including tensile strength and ductility, the creep and lasting properties at 600 degrees C were investigated. Prolonging aging time did not predominantly change the tensile strength and ductility for the two alloys. The 600 degrees C/100 h thermal exposure caused a notable decrease of tensile ductility in 2# alloy though no distinct decrease could be observed in 1# alloy after. the thermal exposure. The lasting property of 1# alloy was increased with prolonging aging time and finally was equal to or even better than that of 2# alloy. Nevertheless, no evident increase emerged in 2# alloy with prolonging aging time. Similarly, the creep property of 1# alloy monotonously increased with increasing aging time and finally was equal to or even better than that of 2# alloy. No evident increase could be observed for 2# alloy. It can be deduced that the overgrowth of alpha(2) ordered phase and silicide is unable to enhance hot strength properties but cause an unacceptable damage to tensile ductility. The optimum equilibrium of the comprehensive properties depending on the proper control Of alpha(2) ordered phase and silicide can be achieved by properly selecting aging temperature and time.
关键词:
Titanium alloy;Mechanical property;Aging treatment;precipitation;phase
