Papers by Keyword: Solution Hardening

Abstract: The casting processes are characterized by complex relationships between predictors and responses. It is the fundamental understanding of these complex relationships that often involves hundreds of factors, which improves quality without losing productivity and raising cost. In this work, cast solid solution strengthened ferritic spheroidal graphite irons GJS-500-14 and GJS-600-10 (EN 1563:2012) have been evaluated. These materials offer stronger components with good machinability owing to their even hardness properties. In this case the predictors are chemical composition, gating layout, foundry set-up, testing procedure and equipment etc. and the responses are the tensile properties (R_p0.2, R_m, A₅). Here 200 tensile specimens compiled from industrial foundry melts from over 30 years of research have created a state-of-the-art platform for statistical engineering in order to perform Exploratory Data Analysis (EDA) and data visualization. This statistical platform has provided new insight on how foundries should treat complex relationships between predictors and responses in order to identify sources of variation and interaction effects.

Abstract: Gamma titanium aluminides (γ-TiAl) have been investigated extensively for more than 25 years, since they are considered to be candidate materials for advanced jet engine components, automobile exhaust valves, turbo-chargers, and so on. Many researchers have reported that the mechanical properties of γ-TiAl have been improved by micro-alloying and thermo-mechanical microstructure control. Recently, γ-TiAl entered a new era by being applied to low-pressure turbine blades in newly developed commercial jet engines. In order to spread their applications further, material durability and affordability have become key issues. The tensile properties of the Ti-Al-X (X=Cr or W) have been studied intensively at various strain rates and test temperatures in a vacuum atmosphere. It has been demonstrated that the additions of a few atomic percent of Cr or W to γ-TiAl shifts the phase stability drastically and creates relatively fine-grain microstructures consisting of α₂+β+γ in three phases. Although the microstructures of Ti-46at%Al-2.7at%Cr and Ti-45at%Al-1.9at%W show similar morphology, the high-temperature mechanical properties of each indicate distinguishable properties. The former specimens have demonstrated the capability of super-plastic deformation at temperatures above 1323K; the latter specimens, however, have showed relatively higher tensile strength than those of the other specimens having ternary compositions (Ti-Al-X). The differences in the tensile properties of Ti-Al-X (X=Cr or W) have been discussed in conjunction with microstructures and the effects of solid-solution hardening due to W atoms.

Abstract: Twin roll casting process combines casting and hot rolling into a single process. In this study, mechanical properties at room temperature and microstructure of the twin roll cast AZ91 magnesium alloy are investigated. The alloy exhibited a good combination of high ultimate strength of 343MPa, yield stress of 224MPa and elongation to failure of 13%. The mechanical property was very excellent compared with AZ91 die-cast alloy. EPMA analysis reveals that the Al concentration in Mg matrix is higher in twin roll cast alloy than that in die-cast alloy. This high Al concentration must be the origin of the good mechanical properties of twin roll cast alloy at room temperature.