Sun Yangshan

Bio: Sun Yangshan is an academic researcher from Southeast University. The author has contributed to research in topics: Creep & Microstructure. The author has an hindex of 11, co-authored 22 publications receiving 761 citations.

Microstructure and mechanical properties of Mg–Al based alloy with calcium and rare earth additions

Abstract: Effects of calcium and rare earth additions to alloy AZ91 on the microstructure and mechanical properties were investigated. The results indicated that small amounts of calcium addition to AZ91 did not cause the formation of any new phases in the microstructure, but refined the as-cast microstructure and increased the thermal stability of the β phase so that the yield strength and creep resistance of the alloy were significantly improved. Additions of lanthanum-rich misch metal (MM) resulted in the formation of needle-shaped particles, which showed very high thermal stability and did not dissolve into the matrix after the solution treatment at 420 °C for 20 h. The strength as well as creep resistance of the alloy at elevated temperatures was remarkably increased when MM was added combined with calcium. The highest creep resistance was obtained from the alloy with 3% of MM and 0.3% of calcium addition and its steady state creep rate reached as low as 2.69×10 −8 s −1 , one order of magnitude lower than that of alloy AZ91 without MM and calcium additions.

Microstructure and tensile creep behavior of Mg–4Al based magnesium alloys with alkaline-earth elements Sr and Ca additions

Abstract: The microstructure, tensile property and creep behavior of three Mg–Al–Sr (AJ) and two Mg–Al–Sr–Ca (AJC) based alloys have been investigated. The as-cast microstructure of Mg–4Al–(1–3)Sr based alloys consists of the dendritic α-matrix and grain boundary second-phases. In the alloy with 1% of strontium added a lamellar eutectic Al4Sr compound is observed at grain boundaries. A ternary Mg–Al–Sr interphase exists at grain boundaries besides eutectic Al4Sr in the alloys containing 2–3% of strontium. Calcium addition to Mg–4Al–(1–2)Sr based alloys results in the formation of Mg2Ca and (Mg, Al)2Ca, which shows two morphologies, lamellar eutectic at grain boundaries and granular in the matrix grains. Creep properties of the Mg–Al–Sr based alloys at the temperatures between 150 and 200 °C and applied stresses between 50 and 80 MPa are significantly improved with the increase of strontium addition and higher creep resistance is obtained from the Mg–4Al–(1–2)Sr based alloys with 1% of calcium addition. The improvements on creep resistance for these alloys studied are mainly attributed to the formation of thermally stable interphases, Al4Sr and Mg–Al–Sr ternary phase as well as Mg2Ca and (Mg, Al)2Ca, which provide the pinning effect at the magnesium grain boundaries. Primarily assessments of creep mechanism based on stress dependence of secondary creep rate at 175 °C and temperature dependence of secondary creep rate at 70 MPa seem that both grain boundary sliding and dislocation climb contribute to the creep deformation.

Effects of bismuth and antimony additions on the microstructure and mechanical properties of AZ91 magnesium alloy

Abstract: The effects of bismuth and antimony additions on the microstructure and mechanical properties of AZ91 alloy have been studied. Results show that a small amount of bismuth or antimony additions to AZ91 increases the yield strength and creep resistance significantly at elevated temperatures up to 200°C. The highest creep resistance has been obtained from the alloy with combined additions of bismuth and antimony. The activation energies of the steady-state creep for AZ91-based alloys studied were close to that of pure magnesium self-diffusion, indicating that dislocation climb is responsible for the creep mechanism under the present conditions. Microstructural observations reveal that the additions of bismuth or antimony have the effect of refining the b (Mg17Al12) precipitates in as-cast alloys and suppressing discontinuous precipitation of the b phase effectively during the aging process. Some rod-shaped Mg3Bi2 or Mg3Sb2 particles distributed mainly at grain boundaries have been observed in the alloys with bismuth or antimony additions. Both Mg3Bi2 and Mg3Sb2 have a high thermal stability and play important roles in improving creep resistance of the alloys at elevated temperatures. © 2001 Elsevier Science B.V. All rights reserved.

Desk handbook phase diagrams for binary alloys

Abstract: Get the phase diagram information you need at a price you can afford. Key Features: Peer reviewed by the Japanese Committee for Alloy Phase Diagrams. Updated through April 2000. Total number of diagrams = 2,332 (605 are new of greatly revised diagrams; among these 171 are not in Binary Alloy Phase Diagrams, 2nd Edition). Approximately 600 crystal structure tables of systems for which phase diagrams are unknown. You've been asking for a simple book containing just binary phase diagrams and crystal structure data. Desk Handbook: Phase Diagrams for Binary Alloys meets this need, and it presents the most current information. Updates the previous print compilation of binary phase diagrams by 10 years. Presents diagrams in consistent size. Shows the principal axis in atomic per cent, with a secondary axis in weight per cent. Includes an introductory article on phase diagrams and their use. Gives reference to the original literature source. This volume is the latest outgrowth of the phase diagram activity in which ASM International has been involved since 1978.

Mechanistic origin and prediction of enhanced ductility in magnesium alloys.

Abstract: Pure magnesium exhibits poor ductility owing to pyramidal [Formula: see text] dislocation transformations to immobile structures, making this lowest-density structural metal unusable for many applications where it could enhance energy efficiency. We show why magnesium can be made ductile by specific dilute solute additions, which increase the [Formula: see text] cross-slip and multiplication rates to levels much faster than the deleterious [Formula: see text] transformation, enabling both favorable texture during processing and continued plastic straining during deformation. A quantitative theory establishes the conditions for ductility as a function of alloy composition in very good agreement with experiments on many existing magnesium alloys, and the solute-enhanced cross-slip mechanism is confirmed by transmission electron microscopy observations in magnesium-yttrium. The mechanistic theory can quickly screen for alloy compositions favoring conditions for high ductility and may help in the development of high-formability magnesium alloys.

Review on Research and Development of Magnesium Alloys

Abstract: The current research and development of magnesium alloys is summarized. Several aspects of magnesium alloys are described: cast Mg alloy, wrought Mg alloy, and novel processing. The subjects are discussed individually and recommendations for further study are listed in the final section.