scholarly journals Mechanical properties and thermal stability of hot-rolled Al–15%B4C composite sheets containing Sc and Zr at elevated temperature

2016 ◽  
Vol 51 (18) ◽  
pp. 2643-2653 ◽  
Author(s):  
Jian Qin ◽  
Zhan Zhang ◽  
X-Grant Chen
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Annealing Time ◽  
Aluminum Matrix ◽  
Tensile Fracture ◽  
Peak Aging ◽  
Hot Rolled ◽  
Thermal Stability Of

The microstructure, mechanical properties, thermal stability and tensile fracture of two hot-rolled Al-15 vol.% B4C composite sheets (S40 with 0.4 wt.% Sc and SZ40 with 0.4 wt.% Sc and 0.24 wt.% Zr) were investigated. During multi-pass hot rolling, coarse Al3Sc or Al3(Sc, Zr) precipitations appeared and resulted in the loss of most of their hardening effect. In an appropriate post-rolling heat treatment, the hot-rolled sheets regained a significant precipitation hardening because of the precipitation of fine nanoscale Al3Sc and Al3(Sc,Zr) that uniformly distributed in the aluminum matrix. After the peak aging, the ultimate tensile strength at ambient temperature of the S40 and SZ40 sheets can reach 198 MPa and 215 MPa, respectively. During 2000 h of annealing at 300℃, the strengths at ambient temperature of both S40 and SZ40 composite sheets slowly decreased with increasing annealing time. However, the tensile strengths at 300℃ of both S40 and SZ40 composite sheets remained nearly unchanged and were less sensitive to the annealing time and more tolerable for precipitate coarsening, which demonstrated an excellent long-term thermal stability of both materials at elevated temperature. The tensile fracture at ambient temperature of both S40 and SZ40 composite sheets was dominated by the brittle B4C particle fracture, whereas the interfacial decohesion of B4C particles became the prominent characteristic of the fracture at 300℃.

Thermal Stability of Retained Austenite in Advanced TRIP Steel with Bainitic Ferrite Matrix for Automotive Industries

2021 ◽  
Vol 1016 ◽  
pp. 429-434
Author(s):  
Eman El-Shenawy ◽  
Hoda Refaiy ◽  
Hoda Nasr El-Din
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Residual Austenite ◽  
Ferrite Matrix ◽  
Sheet Steels ◽  
Coiling Process ◽  
Hot Rolled ◽  
Thermal Stability Of

Multiphase steels consisting of retained austenite and martensite/bainite microstructures such as TRIP, low-temperature-bainite, and Q&P steels are attractive candidates for the new-generation of AHSS. These steels exhibit a remarkable combination of strength and toughness which is essential to meet the objective of weight reduction of engineering-components, while maintaining the compromise of tough-safety requirements. Such good mechanical properties are due to the enhanced work hardening rate caused by austenite-to-martensite transformation during deformation and the strengthening contribution of martensite/bainite. The retained austenite can thermally decompose into more thermodynamically stable phases as a consequence of temperature changes, which is referred to as the thermal stability of retained austenite. TRIP-aided steel is an effective candidate for automotive parts because of safety and weight reduction requirements. The strength–ductility balance of high strength steel sheets can be remarkably improved by using transformation induced plasticity behavior of retained austenite. In manufacturing hot rolled TRIP-aided sheet steels, austenite transforms into bainite during the coiling process. Because black hot coils cool slowly after the coiling process, they are exposed at about 350–450°C for a few hours or days. Therefore, the metastable residual austenite can be decomposed into other phases. This decomposition of residual austenite can produce serious deteriorate of mechanical properties in hot rolled TRIP-aided sheet steels. The present work identified the decomposition behavior and study the thermal stability of retained austenite in the TRIP-aided steel with bainitic/ferrite matrix depending on coiling temperatures and holding times by means of DSC and XRD analysis.

The Influence of Ge on the Properties of Mg Alloys

2015 ◽  
Vol 647 ◽  
pp. 72-78 ◽  
Author(s):  
Jan Šerák ◽  
Tomáš Kovalčík ◽  
Dalibor Vojtěch ◽  
Pavel Novák
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Ambient Temperature ◽  
Magnesium Alloys ◽  
Elevated Temperatures ◽  
Small Extent ◽  
Mg Alloys ◽  
Alloying Elements ◽  
Combustion Engines ◽  
Thermal Stability Of

Germanium is an element which is used in metallurgy in a very small extent. Much more significant is its use as a semiconductor material. Most of magnesium alloys are usually used for applications at ambient temperature. The significant decrease in mechanical properties is observed already at the temperature higher than 150°C. This is the reason for the effort to prepare a new low-priced magnesium based alloys with improved mechanical properties at elevated temperatures, e.g. for components of combustion engines. Therefore, new unconventional alloying elements are studied for increase the thermal stability of magnesium alloys. The effect of germanium on the microstructure and mechanical properties of Mg-Ge alloys at ambient and elevated temperatures was studied in this paper.

Effect of Bi Addition on Thermal Stability and Tensile Ductility of Mg-3%Zn-0.4%Zr Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 647-650
Author(s):  
Joong Hwan Jun ◽  
Min Ha Lee
Keyword(s):  
Thermal Stability ◽  
Tensile Strength ◽  
Elevated Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Ductility ◽  
Grain Structure ◽  
Hot Rolled ◽  
Thermal Stability Of ◽  
Zr Alloy

Thermal stability of  grains and tensile ductilities at room and elevated temperatures were investigated and compared for Mg-3%Zn-0.4%Zr and Mg-3%Zn-0.4%Zr-1%Bi alloys in hot-rolled state. The Bi-added alloy showed slightly finer-grained microstructure with enhanced thermal stability, which is closely associated with fine Mg-Bi compounds acting as obstacles for the migration of grain boundaries. The Mg-3%Zn-0.4%Zr-1%Bi alloy exhibited better tensile strength at room temperature and tensile ductilities at elevated temperature. Finer and more homogeneous grain structure with higher thermal stability would be responsible for the enhanced tensile properties in the Bi-added alloy.

scholarly journals Controlling the Thermal Stability of Kyanite-Based Refractory Geopolymers

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2903
Author(s):  
Juvenal Giogetti Nemaleu Deutou ◽  
Rodrigue Cyriaque Kaze ◽  
Elie Kamseu ◽  
Vincenzo M. Sglavo
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
High Strength ◽  
Treatment Temperature ◽  
Strength Development ◽  
Particle Sizes ◽  
Cold Setting ◽  
Thermal Stability Of ◽  
Geopolymer Composites ◽  
Refractory Composites

The present project investigated the thermal stability of cold-setting refractory composites under high-temperature cycles. The proposed route dealt with the feasibility of using fillers with different particle sizes and studying their influence on the thermo-mechanical properties of refractory geopolymer composites. The volumetric shrinkage was studied with respect to particle sizes of fillers (80, 200 and 500 µm), treatment temperature (1050–1250 °C) and amount of fillers (70–85 wt.%). The results, combined with thermal analysis, indicated the efficiency of refractory-based kyanite aggregates for enhancing thermo-mechanical properties. At low temperatures, larger amounts of kyanite aggregates promoted mechanical strength development. Flexural strengths of 45, 42 and 40 MPa were obtained for geopolymer samples, respectively, at 1200 °C, made with filler particles sieved at 80, 200 and 500 µm. In addition, a sintering temperature equal to 1200 °C appeared beneficial for the promotion of densification as well as bonding between kyanite aggregates and the matrix, contributing to the reinforcement of the refractory geopolymer composites without any sign of vitrification. From the obtained properties of thermal stability, good densification and high strength, kyanite aggregates are efficient and promising candidates for the production of environmentally friendly, castable refractory composites.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

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