Alloy Design Concept Research Articles

Novel Concept of Austenitic Heat Resistant Steels Strengthened by Intermetallics

Alloy design concept for the development of a new class of austenitic heat resistant steels strengthened by Fe2M Laves phases (M: transition metals) has been proposed. The phase diagram studies on Fe-Ni-M ternary systems demonstrate that Fe2Nb with C14 structure is the most promising, because more than 40at% Ni can dissolve into the Fe sublattice sites and large γ+Fe2Nb two-phase region exists along the equi-niobium concentration direction. The control of the c/a ratio of the Laves phase using the composition homogeneity region by alloying makes it possible to disperse the Laves phase finely in the γ matrix. Based on the knowledge, a model alloy Fe-20Cr- 30Ni-2Nb (at%) was proposed and the TTP diagram of the Laves phase was constructed. The Laves phase homogeneously nucleates in the matrix and its fine morphology remains almost unchanged even after long-term aging at 1073K.

Alloy design concepts for refined gamma titanium aluminide based alloys

The influence of the Al content and the addition of further alloying elements on the cast microstructure of γ(TiAl) + α 2(Ti 3Al) alloys has been examined. The results show that particularly fine and homogeneous microstructures without strong segregation can be obtained for certain alloy compositions solidifying through the β phase. This behavior can be attributed to the avoidance of peritectic solidification and to the alloying influence on the kinetics of the β ⇒ α transformation following solidification. The experimental findings were used to propose a design concept for γ-TiAl + α 2-Ti 3Al alloys. This concept aims at the production of high-quality castings as well as at ingot material for wrought processing routes because the chemically homogeneous and fine-grained microstructures would be a good precondition for improved workability.

Design of Bulk metallic glasses with high glass forming ability and enhancement of plasticity in metallic glass matrix composites: A review

To overcome some of the limits of existing metallic alloys, a new alloy design concept has been introduced recently in order to control the crystallinity, i.e. to utilize crystalline, quasicrystalline, and amorphous structures. In particular, bulk metallic glasses (BMGs) receive great attention because of their unique properties due to their different atomic configuration. Recently, significant progress in enhancing glass forming ability (GFA) has led to the fabrication of BMGs having potential for application as structural and functional materials. Moreover, successful design of BMG matrix composite microstructure suggests that the plasticity of BMGs can be controlled properly. In this review article, we introduce recent research results on the design of BMGs with high GFA and on the enhancement of plasticity in metallic glass matrix composites.

Bainitic and martensitic creep-resistant steels

Great advancement has been achieved in the analysis of specific microstructure instability causing a loss of creep strength at 550 °C and above, the prediction of onset time of the creep strength loss and theoretical modeling of precipitation sequences in power plant steels. A number of new alloy-design concepts based on microstructure stabilization have been proposed for the development of highly creep-resistant bainitic 3Cr and martensitic 9–12Cr steels with higher creep rupture strength than existing high strength steels such as T23 and P92.

Nanostructured High‐Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes

A new approach for the design of alloys is presented in this study. These “high‐entropy alloys” with multi‐principal elements were synthesized using well‐developed processing technologies. Preliminary results demonstrate examples of the alloys with simple crystal structures, nanostructures, and promising mechanical properties. This approach may be opening a new era in materials science and engineering.

海浜耐候性鋼の成分設計コンセプト創出

海浜耐候性鋼の成分設計コンセプト創出

Evaluation of the phase stability of modified IN738LC alloys with New Phacomp

At the present time, single-crystal superalloys have the highest temperature capability and the best combination of elevated temperature properties of any structural materials and have been successfully applied as turbine airofoils. Although several special alloys suitable for single-crystal processing have been developed in recent years, only few efforts have been put into the development of so-called "hot corrosion-resistant single-crystal superalloys" which will be suitable for long-term and high-performance marine and industrial gas turbine applications. The purpose of this study is to search for the proper alloy compositions for such alloys with the guide of New Phacomp (PHAse COMPutation). This method is a newly developed alloy design concept based on DV-Xo: cluster calculations of the electronic structure of transition metals [1-3], in which Md and Bo (d-orbital energy level and bond order, respectively, of alloying transition metals) are employed as the parameters controlling the phase stability. In the alloy design process, the average values of Md and Bo are defined by taking the compositional average as