Microstructural development and room temperature tensile property of directionally solidified Ti–47Al alloys by electromagnetic confinement and directional solidification

2018 ◽  
Vol 33 (8) ◽  
pp. 958-966 ◽  
Author(s):  
Yujun Du ◽  
Jun Shen ◽  
Yilong Xiong ◽  
Zhao Shang ◽  
Ling Qin ◽  
...  

Abstract

Author(s):  
J. A. Sutliff ◽  
B. P. Bewlay

In-situ composite Nb-Si alloys have been studied by several investigators as potential high temperature structural materials. The two major processing routes used to fabricate these composites are directional solidification and extrusion of arc-cast solidified ingots. In both cases a stable microstructure of primary Nb dendrites in a eutectoid of Nb and Nb5Si3 phases is developed after heat treatment. The Nb5Si3 phase is stable at room temperature and forms as a decomposition product of the high temperature Nb3Si phase. The anisotropic microstructures developed by both directional solidification and extrusion require evaluation of the texture to fully interpret the fracture and other orientation dependent mechanical behavior of these composites.In this paper we report on the microstructural characterization of a directionally solidified (DS) and heat treated Nb-16 at.%Si alloy. The microtexture of each of the phases (Nb, Nb5Si3) was determined using the Electron BackScattering Pattern (EBSP) technique for electron diffraction in the scanning electron microscope. A system employing automatic diffraction pattern recognition, crystallographic analysis, and sample or beam scanning was used to acquire the microtexture data.


2006 ◽  
Vol 27 (6) ◽  
pp. 494-498 ◽  
Author(s):  
Min-min Wang ◽  
Wei-jie Lu ◽  
Jining Qin ◽  
Fengcang Ma ◽  
Junqiang Lu ◽  
...  

2007 ◽  
Vol 539-543 ◽  
pp. 3690-3695 ◽  
Author(s):  
X.P. Guo ◽  
L.M. Gao ◽  
Ping Guan ◽  
K. Kusabiraki ◽  
Heng Zhi Fu

The microstructure and mechanical properties including room temperature fracture toughness Kq, tensile strengthσb and elongationδ at 1250°C of the Nb based alloy directionally solidified in an electron beam floating zone melting (EBFZM) furnace have been evaluated. The microstructure is primarily composed of Nb solid solution (Nbss), α-(Nb)5Si3 and (Nb)3Si phases. After directional solidification with the moving rate of electron beam gun R being respectively 2.4, 4.8 and 7.2 mm/min, the primary Nbss dendrites, Nbss + (Nb)5Si3/(Nb)3Si eutectic colonies (lamellar or rod-like) and divorced Nb silicide plates align along the longitudinal axes of the specimens. When R = 2.4 mm/min, the best directional microstructure is obtained. Directional solidification has significantly improved theσb at 1250°C and Kq. The maximumσb occurs for the specimens with R = 2.4 mm/min and is about 85.0 MPa, meanwhile, the Kq is about 19.4 MPam1/2.


2015 ◽  
Vol 25 (4) ◽  
pp. 1097-1105 ◽  
Author(s):  
Shu-lin DONG ◽  
Rui-run CHEN ◽  
Jing-jie GUO ◽  
Hong-sheng DING ◽  
Yan-qing SU ◽  
...  

Author(s):  
H.J. Zuo ◽  
M.W. Price ◽  
R.D. Griffin ◽  
R.A. Andrews ◽  
G.M. Janowski

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.


2012 ◽  
Vol 1516 ◽  
pp. 255-260 ◽  
Author(s):  
G. Zhang ◽  
L. Hu ◽  
W. Hu ◽  
G. Gottstein ◽  
S. Bogner ◽  
...  

ABSTRACTMo fiber reinforced NiAl in-situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification (DS) using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. In these composites, single crystalline Mo fibers were precipitated out through eutectic reaction and aligned parallel to the growth direction of the ingot. Mechanical properties, i.e. the creep resistance at high temperatures (HT, between 900 °C and 1200 °C) and the fracture toughness at room temperature (RT) of in-situ NiAl-Mo composites, were characterized by tensile creep (along the growth direction) and flexure (four-point bending, vertical to the growth direction) tests, respectively. In the current study, a steady creep rate of 10-6s-1 at 1100 °C under an initial applied tensile stress of 150MPa was measured. The flexure tests sustained a fracture toughness of 14.5 MPa·m1/2at room temperature. Compared to binary NiAl and other NiAl alloys, these properties showed a remarkably improvement in creep resistance at HT and fracture toughness at RT that makes this composite a potential candidate material for structural application at the temperatures above 1000 °C. The mechanisms responsible for the improvement of the mechanical properties in NiAl-Mo in-situ composites were discussed based on the investigation results.


2011 ◽  
Vol 687 ◽  
pp. 500-504
Author(s):  
S. X. Xue ◽  
S.S. Feng ◽  
P. Y. Cai ◽  
Q T Li ◽  
H. B. Wang

Ni54Mn21-xFexGa25(x=0,1,3,5,7,9)polycrystalline alloys were prepared by the technique of directional solidification and the effect of substituting Fe for Mn on the martensitic transformation and mechanical properties of the alloys was analyzed. It was found that the Curie temperature increased with increasing substitution while the martensitic transformation temperature decreased. The Fe-doped Ni54Mn21Ga25 alloys exhibit excellent magnetic properties at room temperature; the typical Ni54Mn20Fe1Ga25 alloy shows a large magnetic-induced-strain of -1040 ppm at a magnetic field of 4000 Oe.


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