Ternary MoSi2 Compounds for High Temperature Structural Applications

1993 ◽  
Vol 322 ◽  
Author(s):  
S. Chin ◽  
D. L. Anton ◽  
A. F. Giamei
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Isothermal Oxidation ◽  
Phase Boundaries ◽  
Brittle Transition ◽  
Flexural Testing ◽  
Structural Applications ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Oxidation Testing

AbstractThe microstructure and phase composition of MoSi2 modified with Al, B, Ge, Hf, Nb, and Re have been investigated. B and Hf substitutions for Si and Mo, respectively, exhibited very low solubilities in MoSi2. Al and Nb substitutions for Si and Mo, respectively, changed the crystal structure from tetragonal C11b to hexagonal C40. Phase boundaries and solubility limits were determined for Al and Nb substitutions. Ge and Re substitutions for Si and Mo, respectively, exhibited complete solubility and maintained the tetragonal Cllb crystal structure. The mechanical properties evaluation as determined by four-point flexural testing indicate a ductile-to-brittle transition temperature (DBTT) of 1250-1350°C for all of the modifications evaluated. Isothermal oxidation testing at 1400°C indicates no significant debit in oxidation resistance of MoSi2 that can be attributed to alloying, however, alloys containing higher concentrations of the ternary elements may exhibit reduced oxidation resistances.

The Effects of Grain Size on the Flow and Fracture of Long-Range Ordered Alloys

1984 ◽  
Vol 39 ◽  
Author(s):  
Erland M. Schulson
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Refinement ◽  
Low Temperatures ◽  
Ferritic Steels ◽  
Brittle Transition ◽  
Ordered Alloys ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Grain Refinement Strengthening

Three points usually come to mind when considering the effects of grain size on the mechanical properties of polycrystals: strengthening at low temperatures through grain refinement, strengthening at high temperatures through grain coarsening, and lowering of the ductile to brittle transition temperature in materials such as ferritic steels and zinc through grain refinement. Ordered alloys, as we shall see, exhibit the same effects.

scholarly journals Mechanical Properties and Impact Toughness of Molybdenum Alloyed Ductile Iron

2020 ◽  
Author(s):  
D. Franzen ◽  
B. Pustal ◽  
A. Bührig-Polaczek
Keyword(s):  
Mechanical Properties ◽  
Transition Temperature ◽  
Ductile Iron ◽  
Calculated Data ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Brittle Transition ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
High Silicon

Abstract Grades of high silicon ductile iron offer excellent combinations of static strength and ductility as well as good machinability due to their fully ferritic, solution strengthened matrix. As a result of elevated silicon contents, however, the ductile-to-brittle transition temperature in the Charpy impact test is significantly increased. Thus, minimum required Charpy impact energies cannot be met for many applications by using high silicon ductile iron. Therefore, alloys with lower strength and higher toughness properties are commonly used for many technical applications. The enormous lightweight construction potential of high silicon ductile iron can therefore not be fully exploited. The present investigation pursues the metallurgical approach of partially substituting silicon with molybdenum as an alternative strengthening element in order to improve the toughness properties while maintaining similar static mechanical properties. Molybdenum serves as a carbide-stabilising element in ductile iron, while simultaneously promoting ferrite formation and is therefore regarded to be suitable alloying element. In Charpy impact tests, the ductile-to-brittle transition temperature could be reduced by about 55 °C by reducing the silicon content to 2.95 wt% and adding 0.21 wt% molybdenum compared to a high silicon alloy. Additionally, it was possible to mathematically describe the transition behaviour of the studied alloys using nonlinear regression functions and to achieve a sufficient correlation of empirically determined and calculated data. This present metallurgical concept offers a promising metallurgical tool for further improving the toughness properties of alloyed ductile iron.

Microstructures and Mechanical Properties of Directionally Solidified Intermetallic Composites

2007 ◽  
Vol 539-543 ◽  
pp. 1495-1500 ◽  
Author(s):  
H. Bei ◽  
E.P. George
Keyword(s):  
Mechanical Properties ◽  
Growth Rate ◽  
Tensile Tests ◽  
Square Root ◽  
Directionally Solidified ◽  
Brittle Transition ◽  
Fiber Size ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Nial Matrix

This paper reviews two kinds of well-aligned fibrous microstructures produced by directional solidification of NiAl-Mo and Fe-Fe2Ta eutectics. In both these composites, fiber size and spacing decrese inversely as the square root of the growth rate. Tensile tests as a function of temperature showed that the NiAl-Mo composite has a higher yield strength and lower ductile-to-brittle transition temperature than the NiAl matrix. For the Fe-Fe2Ta composite, yield strengths in excess of 700 MPa were obtained at temperatures to 600°C, with elongations to fracture of ~3% which remained roughly constant at temperatures to 950°C.

Static and Cyclic Behavior of Welded DH36 Steel and Its Application at Low Temperatures

2021 ◽  
pp. 1-31
Author(s):  
Weidong Zhao ◽  
Guoqing Feng ◽  
Bernt J. Leira ◽  
Huilong Ren
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Fatigue Tests ◽  
Cyclic Behavior ◽  
Brittle Transition ◽  
Ductile To Brittle Transition

Abstract The mechanical properties of welded DH36 steel at low temperatures are important to the safety of structures in Polar areas. The purpose of the study is to investigate the static and cyclic behavior of welded DH36 steel at low temperatures based on tensile and fatigue tests. The Ductile to Brittle transition and Fatigue Ductile to Brittle Transition of welded DH36 steel occurred at low temperatures. Finally, some relevant applications of the results within the context of polar engineering and design are discussed in the last part of the present study.

scholarly journals A Study of Fracture Mechanisms in RAFM Steel in the Ductile to Brittle Transition Temperature Regime

2014 ◽  
Vol 86 ◽  
pp. 258-263 ◽  
Author(s):  
A. Moitra ◽  
Arup Dasgupta ◽  
S. Sathyanarayanan ◽  
G. Sasikala ◽  
S.K. Albert ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Temperature Regime ◽  
Fracture Mechanisms ◽  
Brittle Transition ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Rafm Steel

scholarly journals Fractographic Analysis Of Selected Boron Steels Subjected To Impact Testing

2015 ◽  
Vol 60 (3) ◽  
pp. 2373-2378 ◽  
Author(s):  
W. Dudziński ◽  
Ł. Konat ◽  
B. Białobrzeska
Keyword(s):  
Transition Temperature ◽  
Impact Testing ◽  
Transition Curve ◽  
Brittle Transition ◽  
Significant Difference ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Character Of Fracture ◽  
The Impact ◽  
Boron Steels

Abstract In this paper dynamic properties of low-alloy boron steels – Hardox 500, B27 and HTK 900H in delivered state (after hardening and tempering) are considered. Charpy V-notch (CVN) test results in connection with fractography in the ductile-to-brittle transition temperature region were analyzed. Obtained from CVN test the impact transition curve, not always predicts properly a behavior of materials in conditions of dynamic loading. So an analyze of character of fracture helps to evaluate the real behavior of materials. Tested samples were cut out longitudinally in relation to cold work direction. The results of CVN test for selected steels, in temperatures: −40°C, −20°C, 0°C and +20°C are presented. Regarding ductile-to-brittle transition temperature, there is a significant difference taking into account values of Charpy V energy absorbed and a character of fracture.

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