マルチスケール制御によるトレードオフ・バランシング高性能マグネシウム合金の創製

2002 Fiscal Year Annual Research Report

• Project/Area Number: 11225209
• Research Institution: Osaka Prefecture University
• Principal Investigator: 東 健司 大阪府立大学, 工学研究科, 教授 (50173133)
• Co-Investigator(Kenkyū-buntansha): 向井 敏司 大阪市立工業研究所, 機械課, 主任研究員 ; 高津 正秀 大阪府立大学, 工学研究科, 講師 (80145812)
• Keywords: マルチスケール制御 / トレードオフバランシング / 第一原理分子動力学 / 微細化プロセス / 結晶方位制御 / 拡散接合 / プレス成形性 / 切欠き感受性

Research Abstract

本研究は、電子・原子レベルからマクロまでのマルチスケール制御によるトレードオフバランシングされた高性能マグネシウム合金の創製を目的とし、(1)第一原理分子動力学計算による変形挙動の解析と合金設計、(2)機械的特性や成形性に優れた合金の創製プロセスの構築、(3)拡散接合および摩擦撹拝溶接技術の確立、(4)圧延板からのプレス成形技術の確立、の4つに大別できる。
(1)では、マグネシウムの脆さの原因となる底面と非底面の臨界分解せん断応力の大きな差を、単結晶の理想すべり変形における積層欠陥エネルギーの計算から論じ、Li、Al、Znのいずれの添加でもその差が小さくなることを見出した。また、結合強度の異方性を電子密度分布から論じた。
(2)では、拘束型押出しによるMg-Zn系合金へのZr系析出物微細分散と結晶粒微細化による衝撃特性の向上を達成した。また、ECAEによるAZ31合金の結晶粒微細化と方位制御による伸びのひずみ速度逆依存性が見出され、1.8×10^3_S^<-1>の室温高速引張下で50%もの飛躍的な伸びの向上を達成した。また、種々の合金において低温ないし高速超塑性が発現することを明らかにした。
(3)では、圧縮場での超塑性変形における空洞消滅モデルから拡散接合条件式を導き、AZ31合金が、最適条件下では、アルミニウムの1/3の接合時間で十分な接合強度が得られることを示した。また、摩擦攪拌接合では、純マグネシウムは空洞成長により十分な接合強度が得られないが合金では母材の90%以上の接合強度が得られた。
(4)では、深絞りの成形限界がポンチ肩上での引張曲げによる破断限界に依存し、473K以下の加熱によりそれが向上することを示した。また、引張試験では評価し難い局所的な変形能がプレス成形性の向上に重要であることを示し、切欠き感受性試験による成形性評価を提唱した。

Research Products

• [Publications] Watanabe, Hiroyuki: "High-strain-rate superplasticity at low temperature in a ZK61 magnesium alloy produced by powder metallurgy"Scripta Materialia. 41・2. 209-213 (1999)
• [Publications] Mukai, Toshiji: "Dynamic compressive behavior of an ultra-lightweight magnesium foam"Scripta Materialia. 41・4. 365-371 (1999)
• [Publications] Watanabe, Hiroyuki: "Low temperature superplastic behavior in ZK60 magnesium alloy"Materials Science Forum. 304-306. 303-308 (1999)
• [Publications] Watanabe, Hiroyuki: "Observation of high-strain-rate superplasticity in ZK60 and SiCp/ZK60 composite"Materials Science Forum. 304-306. 297-302 (1999)
• [Publications] Watanabe, Hiroyuki: "Low temperature superplasticity in a ZK60 magnesium alloy"Materials Transactions, JIM. 40-8. 809-814 (1999)
• [Publications] Watanabe, Hiroyuki: "Effect of Temperature and Grain Size on the Dominant Diffusion Process for Superplastic Flow in an AZ61 Magnesium Alloy"Acta Materialia. 47・14. 3753-3758 (1999)
• [Publications] Tsutsui, Hirosuke: "Superplastic deformation behavior in commercial magnesium alloy AZ61"Materials Transactions, JIM. 40・9. 931-934 (1999)
• [Publications] Watanabe, Hiroyuki: "Superpliasticity at low temperatures in a ZK61 magnesium alloy produced by powder metallurgy"Key Engineering Materials. 171-174. 363-368 (2000)
• [Publications] Mukai, Toshiji: "Experimental study of the mechanical properties at elevated temperatures in commercial Mg-Al-Zn alloys for superplastic forming"Key Engineering Materials. 171-174. 337-342 (2000)
• [Publications] Watanabe, Hiroyuki: "Low temperature superplasticity in a magnesium-based composite"Scripta Materialia. 42-3. 249-255 (2000)
• [Publications] Mukai, Toshiji: "Application of superplasticity in commercial magnesium alloy for fabrication of structural components"Materials Science and Technology. 16・11-12. 419-422 (2003)
• [Publications] Watanabe, Hiroyuki: "Superplasticity of a particle-strengthened WE43 magnesium alloy"Materials Transactions, JIM. 42-1. 157-162 (2003)
• [Publications] Watanabe, Hiroyuki: "Deformation mechanism in a coarse-grained Mg-Al-Zn alloy at elevated temperatures"International Journal of Plasticity. 17・3. 387-397 (2001)
• [Publications] Somekawa, Hidetoshi: "The press formability in magnesium alloy AZ31"Materials Science Forum. 350-351. 177-182 (2000)
• [Publications] Watanabe, Hiroyuki: "Superplastic behavior in commercial wrought magnesium alloys"Materials Science Forum. 350-351. 171-176 (2000)
• [Publications] Mukai, Toshiji: "Grain refinement of commercial magnesium alloys for high-strain-rate-superplastic forming"Materials Science Forum. 350-351. 159-170 (2000)
• [Publications] Mukai, Toshiji: "Ductility enhancement in magnesium alloys under dynamic loading"Materials Science Forum. 350-351. 97-102 (2000)
• [Publications] Watanabe, Hiroyuki: "Realization of high-strain-rate superplasticity at low temperatures in a Mg-Zn-Zr alloy"Materials Science and Engineering A : Structual Materials Properties Microstructure and Processing. 307・1-2. 119-128 (2001)
• [Publications] Kanahashi, Hidenori: "Experimental study for the improvement of crashworthiness in AZ91 magnesium foam controlling its microstructure"Materials Science and Engineering A : Structual Materials Properties Microstructure and Processing. 308・1-2. 283-287 (2001)
• [Publications] Mukai, Toshiji: "Grain refinement of a commercial magnesium alloy for superplastic forming"Materials Science Forum. 357-359. 459-464 (2001)
• [Publications] Watanabe, Hiroyuki: "Effective diffusivity for superplastic flow in magnesium alloys"Materials Science Forum. 357-359. 147-152 (2001)
• [Publications] Watanabe, Hiroyuki: "Superplastic deformation mechanism in powder metallurgy magnesium alloys and composites"Acta Materialia. 49・11. 2027-2037 (2001)
• [Publications] Masahide, Kohzu: "Fracture Mechanism and Forming Limit in Deep-Drawing of Magnesium Alloy AZ31"Materials Transactions. 42・7. 1273-1276 (2001)
• [Publications] Watanabe, Hiroyuki: "Grain size control of commercial wrought Mg-Al-Zn alloys utilizing dynamic recrystallization"Materials Transactions. 42・7. 1200-1205 (2001)
• [Publications] Mukai, Toshiji: "Effect of grain refinement on tensile ductility in ZK60 magnesium alloy under dynamic loading"Materials Transactions. 42・7. 1177-1181 (2001)
• [Publications] Uesugi, Tokuteru: "Ab Initio Calculation on the Structure and Elastic Properties of A Magnesium-Lithium Alloy"Materials Transactions. 42・7. 1167-1171 (2001)
• [Publications] Mukai, Toshiji: "Ductility enhancement in AZ31 magnesium alloy by controlling its grain structure"Scripta Materialia. 45・1. 89-94 (2001)
• [Publications] Watanabe, Hiroyuki: "Consolidation of machined magnesium alloy chips by hot extrusion utilizing superplastic flow"Journal of the Materials Science. 36・20. 5007-5011 (2001)
• [Publications] Somekawa, Hidetoshi: "Experimental study on diffusion bonding in pure magnesium"Materials Transactions. 42・10. 2075-2079 (2001)
• [Publications] Mukai, Toshiji: "Processing of ductile magnesium alloy under dynamic tensile loading"Materials Transactions. 42・12. 2652-2654 (2001)
• [Publications] Watanabe, Hiroyuki: "High-strain-rate superplasticity in an AZ91 magnesium alloy processed by ingot metallurgy route"Materials Transactions. 43・1. 78-80 (2002)
• [Publications] Watanabe, Hiroyuki: "Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion"Scripta Materialia. 46・12. 851-856 (2002)
• [Publications] Somekawa, Hidetoshi: "Diffusion bonding in superplastic magnesium alloys"Materials Science and Engineering A : Structual Materials Properties Microstructure and Processing. 339・1-2. 328-333 (2003)
• [Publications] Somekawa, Hidetoshi: "Diffusion bonding in commercial superplastic AZ31 magnesium alloy sheets"Key Engineering Materials. 233-254. 857-862 (2003)
• [Publications] Mukai, Toshiji: "Guide for Enhancement of Room Temperature Ductility in Mg Alloys at High Strain Rates"Materials Science Forum. 419-422. 419-422 (2003)
• [Publications] Somekawa, Hidetoshi: "The Diffusion Bonding and Theoretical Model Including Void Growth Mechanism in Magnesium Alloys"Materials Science Forum. 419-422. 393-398 (2003)
• [Publications] Uesugi, Tokuteru: "Generalized Stacking Fault Energy and Dislocation Properties for Various Slip Systems in Magnesium : a First-Principles Study"Materials Science Forum. 419-422. 225-230 (2003)
• [Publications] Yoshikawa, Masahiro: "Quality Improvement of Rapidly Solidified Magnesium Alloy by Plastic Processing"Materials Science Forum. 419-422. 769-776 (2003)
• [Publications] Kohzu, Masahide: "Evaluation of Press Formability in Magnesium Alloy"Materials Science Forum. 419-422. 321-326 (2003)
• [Publications] Chung, Sung Wook: "Superplastic Deformation Behavior in the Commercial AZ61 Mg Alloy during Biaxial Gas-pressure Forming"Materials Science Forum. 419-422. 539-544 (2003)