ØSrÚCa Mg 12Zn 4Al 0.3MnÜ

Ñ 45 µ Ñ 5 Å Vol.45 No.5 2009 Ü 5 Ñ 585 591 Ò ACTA METALLURGICA SINICA May 2009 pp.585 591 ØSrÚCa Mg 12Zn 4Al 0.3MnÜ Ú º± 1) ¼µ 1,2)» ² 1,2) 1,2) ¹³ 3) 1) ÙÓ Ä¼ Ź, Ó 211189 2) Đ ½ Ä Ð ÔÀ Ì, Ó 211189 3) Đ Å Ä¹ Ð Â, Ó 211224 Ø Mg 12Zn 4Al 0.3Mn( À, %) Æ,  6 Æ. Á ½ Á, Mg 12Zn 4Al 0.3Mn Æ Û α Mg Đ ³ Ç Q. Æ À Sr Í, Ç Ã Mg 32(Al, Zn) 49 Ê Ø Mg 51Zn 20 ¼. Æ Æ Sr «Ca Í, Û Á  Al 2Mg 5Zn 2 ¼. ÔÉ Sr À, Æ Í Â» ÝÐ, µ ÈÙ» ; Sr «Ca Æ ÄÆ ¹ Ý Ȼ, ÝÐ. 175 /70 MPa ß», Mg 12Zn 4Al 0.2Sr 0.4Ca 0.3Mn Æ Á ¹µ ÈÙ. ÖÞ Æ,, ÈÙ, ¹µ ÈÙ ÒÕ Ù TG146.2 Å A Ù 0412 1961(2009)05 0585 07 MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Mg 12Zn 4Al 0.3Mn ALLOY CONTAINING Sr AND Ca WAN Xiaofeng 1), SUN Yangshan 1,2), XUE Feng 1,2), BAI Jing 1,2), TAO Weijian 3) 1) School of Materials Science and Engineering, Southeast University, Nanjing 211189 2) Jiangsu Key Laboratory for Advanced Metallic Materials, Nanjing 211189 3) Jiangsu Engineering Research Center for Magnesium Alloys, Nanjing 211224 Correspondent: SUN Yangshan, professor, Tel: (025)52090689 20, E-mail: yssun@seu.edu.cn Supported by National Key Basic Technology R&D Program of China (No.2006BAE04B07) and Special Program for the Commercialization of Key Science and Technology Achievements Financed by Jiangsu Science and Technology Department (No.BA2005004) Manuscript received 2008 05 06, in revised form 2008 10 24 ABSTRACT Magnesium alloys have emerged as potentially good candidates for numerous applications, especially in automotive industry. Although the commonly used magnesium alloys, such as AZ91 and AM60 based on Mg Al system have excellent castability, good room temperature mechanical properties and low cost, the application of these alloys has been limited to temperatures below 120 because of their poor heat resistance, especially creep property at elevated temperatures. Recent development reported that magnesium alloys with high zinc and low aluminum concentrations (Mg Zn Al based alloys) exhibit better creep properties than Mg Al based alloys at temperatures above 150 and small amounts of alkaline earth element (Sr and Ca) additions to the Mg Zn Al ternary alloys lead to further improvement of their mechanical properties. The purpose of the present paper is to describe the effects of calcium and strontium additions on the microstructure and mechanical properties of Mg 12Zn 4Al 0.3Mn based alloy. The results indicate that the as cast microstructure of Mg 12Zn 4Al 0.3Mn alloy consists of the α Mg matrix and a quasicrystalline Q phase at grain boundaries. Small amounts of Sr addition to the master alloy result in the transition of metastable Q phase to the equilibrium * սѲ Ò 2006BAE04B07  ½Ñ Ã Â Ë BA2005004 Ë ² «: 2008 05 06, Ë ² «: 2008 10 24 ÜÆ :, Õ, 1980 Ý, È

586 Ñ 45 µ Mg 32 (Al, Zn) 49 phase and the formation of binary eutectic phase Mg 51 Zn 20. Another lamellar eutectic phase Al 2 Mg 5 Zn 2 is observed in the as cast microstructure when Ca combined with Sr is added to the base alloy, and its volume fraction increases with increase of Ca addition. The single addition of Sr causes the increase of tensile strength, but decrease of creep resistance at elevated temperatures. However, the creep properties are significantly improved if Sr is added in combination with Ca to the master alloy due to the formation of ternary eutectic phase Al 2 Mg 5 Zn 2, which shows the high thermal stability at elevated temperatures. The alloy with composition of Mg 12Zn 4Al 0.2Sr 0.4Ca 0.3Mn exibits good creep resistance at 175 and 70 MPa. KEY WORDS magnesium alloy, microstructure, mechanical properties, creep resistance Ð ß Ç Û Mg Al ¹ Æ, AZ91 à AM60. Ç Ô«½Ú ¼ Ü, º Þ 120 Î, Ç Þú ÉÚ Þ¼. 20 Þ, Mg Al ¹ Ç Ø RE, Ca à Si Æ Ç Ò ÉÚ, ÃÉÀ À. ± Ç À ÉÚ Ã Ø, Ã Ç Â [1,2]. ÝÇ ³ ÀÎÇ ÉÚ Ò Ç, ÊÐ Ç È Õ. Zn Ç (Mg Zn Al ¹) ³, À Ã Ò ÉÚ Õ, ³ À Ãß [3 6]. Zhang [7] Đ Zn Á 8% 14%( Á, ¼ ), Al Á 2% 6% Ç Ã ¹,»Â Al Á 4%, Ç ³ À ÎÇÉ Ú., Ù ÃÛ Ca عÎĐÇ ÉÚ [8]. Zhang º Å, Ù Mg 12Zn 4Al 0.3Mn( Á, %) Ç, ÜØ ¹Æ Sr, Ù Çع Sr à Ca Æ, ¹ à 2 Û Æ ĐÇ Ã ÉÚ. 1 ÓÑ Â ½ à 6 Ç ( 1). No.1 Ç (ZA124, Mg 12Zn 4Al 0.3Mn) Ç, Ú 5 Ç Ê ÙÇ Mg 27%Sr à Mg 30%Ca Ç Ø¹± Á Sr à Ca. ¹ Æ Ì², Å Ç Æ ² Î, Å ÆÃÔØ Î. ² à Á ¹ 99%CO 2 +1%SF 6 ( ) ÇÆ Ï. ² Î, ÓÜÇ 700 ¼ 10 min Î, ¹ Cu.  WD 10A ÖÌ Ú 1 Ã È Table 1 Compositions of the alloys prepared (mass fraction, %) Alloy Mg Zn Al Sr Ca Mn No.1 (ZA124) Bal. 12.0 4.0 0.3 No.2 (ZAJ12402) Bal. 12.0 4.0 0.2 0.3 No.3 (ZAJ12406) Bal. 12.0 4.0 0.6 0.3 No.4 (ZAJ12408) Bal. 12.0 4.0 0.8 0.3 No.5 (ZAJX1240202) Bal. 12.0 4.0 0.2 0.2 0.3 No.6 (ZAJX1240204) Bal. 12.0 4.0 0.2 0.4 0.3 Æ, Æ ³ ¹ ÉÀ Á, Î 18 mm 3.2 mm 1.8 mm. Å Ö È (GB/T 2039 1997) غ, ¹ à 10 à 100 mm.  RD2 3 Ã È Æ, 175 /70 MPa, 100 h. à 2 3  ² º. ¹ 4% Ñ ³Ó. Ç Olympus BHM à Sirion ½ Ö (SEM) Æ ¾. ¹ SEM Ú (EDXS) Ã Ö (TEM) Ø. (DSC)  ³ ËÚ Ar Ï NET- ZSCH STA449C à ǽ Á Ö Æ, Þ«30 700, Î 20 /min. 2 ß 2.1 ÝÐÐ ««1 ØÇ Ç. No.1 Ç α Mg Ã Ê ÆÒ («1a). Sr عÎ, Ç Ã,  à 2 ± Å Ù ( «1b A à B ØÇ). 2 Ù Ã Å Ç, A Æ Ç É, Þ, ÖÙ Â Ù, B Æ Ù Þ No.1 Ç Ù, Ú Å Ç, α Mg Æ, ÉÅ ÉÖ ØÚÊÑ Åß ². Ca Sr ÇعÎ,  à ƽ («1c C ØÇ), Õ Ca Á Ø, ½ («1d). «2a No.1 Ç SEM. «¾Þ, Ù Ê, Å ±. Ç Ù TEM «2b Ø Ç, ¼«ß ÖÌ (SAED), Ú³ 5 È ÄĐ, ¾Ù Ø Ù ÊÔ È, Ú Q. EDXS ( 2), Q Mg, Zn à Al, Mg Zn Al»Æ¹ Mg 32 (Al, Zn) 49 [9]. «3a Ê No.3 Ç ÀÜ SEM. Æ («3a A Æ) Ê ¾ Þ Ç («1b A Æ), Å ½ ². 2 EDXS Ç,»Æ½ Mg, Zn à Á Al Æ. «3b à c ÊÚ TEM Ã

Ñ 5 Å : Sr Á Ca Mg 12Zn 4Al 0.3Mn Å µá ÇØ 587 Æ 1 Æ Û Fig.1 As cast microstructure of alloys No.1 (a), No.3 (b), No.5 (c) and No.6 (d) Æ 2 No.1 Æ SEM Ä Â Q TEM ½ Fig.2 SEM micrograph (a) and TEM micrograph of Q phase in alloy No.1 and corresponding SAED pattern (the insert) taken from the Q phase (b) 2 Ú Û µå Table 2 Results of EDXS analyses obtained from intermediate phases in the alloys studied (atomic fraction, %) Phase Mg Zn Al Ca Sr Q (Fig.2a) 51.3 33.7 15.0 ε (A in Fig.3a) 73.4 22.1 4.4 τ (B in Fig.3a) 38.9 32.5 25.7 2.8 ϕ (C in Fig.4a) 60.3 15.9 20.9 1.2 1.4 ß SAED. Ø, ØÇ Mg 51 - Zn 20, ¹ ( Ù Immm, a=1.4083 nm, b=1.4486 nm, c=1.4025 nm) [10], Ô«ε. «3a ¾ ÉÔ Ç («1b B Æ), EDXS ( 2), Æ Ù Mg, Zn à Al Ç È Q, Á Sr. SAED, Úʳ bcc ¾ Mg 32 (Al, Zn) 49 ( Ù T 5 h, a=1.416 nm)[11], ß SAED Ç «3d, Ô«τ. ¾Þ, È Q Ê Ë τ ±Ü. τ ÃÈ Q Å Æ, ÝDZÚÐà Sr Ç Ñ Á Q Í ¾ÚÉ. No.6 Ç ÀÜ SEM Ç «4a. ¾ ƽ («1c C Æ)

588 Ñ 45 µ Æ 3 No.3 Æ SEM  TEM ½Ø SAED Fig.3 SEM micrograph (a) and TEM bright field image (b) taken from No.3 alloy, and SAED pattern of α Mg matrix and ε (c) and SAED pattern of τ (d) Æ 4 No.6 Æ SEM  TEM ½Ø SAED Fig.4 SEM micrograph (a) and TEM bright field image (b) taken from No.6 alloy, and SAED pattern of α Mg matrix and ϕ (c) SEM. 2 EDXS Ç, ½ Ò Ð Mg, Zn à Al, Ù Á Sr à Ca. «4b à c Ç ½ TEM ß SAED, Ø, ؽ ¹ ¾ Al 2 Mg 5 Zn 2 ( Ù Pbcm, a=0.90 nm, b=1.70 nm, c=1.97 nm) [12], ϕ. Ç ¾ ¼: (1) ZA124 Ç Ð α Mg ó È Q (2) Ç Ø¹ Á Sr Î, Ç È Ä Ë τ, Ú ÃÅ È Q Æ. Ç,»Æ ε ½ (3) Ca Ø¹Î Â Ã Æ ½ ϕ, ÕÊ Ca عÁ Ø, ϕ. 2.2 ÝÐÐ Ç ÀÜ Î Ã (200 ) ß É ÚÆ 3. Đ Sr Ç (No.2 4), Õ Sr ع Á Ø, Î º Þ σ b Ã Î δ ¾ μ É. Sr ÁÏ 0.6%(No.3 Ç ), Ç σ b à δ Ï º, 199 MPa à 2.4%. Ç (No.1), σ b à 23%; ± Ôµ Ø Sr عÁÎ, Ç σ b Å ¼. 200 ¼, Ó Ç σ b ÑÕ Sr Á Ø ¾ Ø ÎÝ É, ÐÉ ÐÝ. Sr عÁÏ 0.8% (No.4 Ç ), Ç ÉÚ ¾ Ç. Sr عÁ 0.2% ¼, ع Á Ca(No.5 à No.6) Î, Ç Î Ã ¼ σ b à δ Û Ø¼, Þ (σ 0.2 ) Ï. ÜØ Sr Ç, Ca Sr ÇÇ Î, Ç

Ñ 5 Å : Sr Á Ca Mg 12Zn 4Al 0.3Mn Å µá ÇØ 589 à ÉÚ ¼ É. 2.3 ÝÐÐ «5a ØÇ Ê Ç 175 /70 MPa ¼, «5b ÆÂà 100 h Î Ç ÎÃß Á. Àܼ, No.1 Ç ±Ü ÎÃß 1.01 10 8 s 1 à 0.57%, º ÉÚ º ¼ AZ91 à AM60 Mg Al ¹ Ç [13]. 100 h Î, Ç ÛÍ Ò 2, ÜØ Sr 3 Ç (No.2 4) ÎÉ, Îà 100 h Îß Á Ç (No.1). ع Sr à Ca 2 Ç (No.5 à No.6) À º ÉÚ, Õ Ca عÁ Ø, Ç ÎÃ ß ÏÁ Ý, ع 0.2%Sr 3 È Ï Ä± ÊÛ Table 3 Tensile properties of alloys at room temperature and 200 Alloy Room temperature 200 No. σ b σ 0.2 δ σ b σ 0.2 δ MPa MPa % MPa MPa % 1 162 140 1.3 133 114 3.4 2 171 149 2.1 167 135 4.6 3 199 147 2.4 170 142 4.1 4 170 138 1.4 148 129 1.9 5 173 151 1.3 158 140 2.0 6 161 154 1.0 158 146 1.6 Creep strain, % Minimum creep rate, 10-9 s -1 1.2 0.8 0.4 0.0 30 25 20 15 10 5 (a) No.1 No.2 No.3 No.4 No.5 No.6 0 20 40 60 80 100 120 Time, h 3.0 (b) 23.3 2.5 10.1 Minimum creep rate 100 h creep strain 0.57 13.0 0.84 11.8 0.72 1.00 7.41 7.13 0.42 0.35 0 0.0 No.1 No.2 No.3 No.4 No.5 No.6 Sample Æ 5 175 /70 MPa»µÆ µ Ø µ Í Â Þ Í Fig.5 Creep curves (a) and minimum creep rate and 100 h creep strain (b) of alloys at 175 /70 MPa 2.0 1.5 1.0 0.5 100 h creep strain, % à 0.4%Ca Î No.6 Ç ±Ü Î (7.13 10 9 s 1 ) Ç ¼ à 30%, 100 h ß Á (0.35%) Ñ Ç ß Á 60%, Ï Ã 6 Ç Ôº. 3 Ô 3.1 ¹ Vogel [14] ¾, À ¼ ZA85 Ç ³ ¾ È, [15,16], Đ Mg Zn Al ¹Ç, ½ ß ¼ Å È. Cu À ZA124(No.1) Ç, Ñ Ã È, Ô µ±âã ZA ¹Ç È Æ ß ¼ÑÚ Å, Vogel [14] Ô. ²Đ No.1 Ç ( Ç ) Æ DSC, DSC («6) 2 («I à II), Đß ³ ² ÃÒ Ä. Ç Mg Zn Al»ÆÓ «[9,17], ¾Ù ÐÇ ZA124(No.1) Ëß ¼Åß: (1) 590 Å À α Mg ; (2) 350, ½ Åß: L 1 α Mg+ϕ+L 2, ϕ ; (3) ÕÎ ϕ Ó L 2 Åß: L 2 +ϕ α Mg+τ+L 3 ; (4) Ó ½ Åß: L 3 α Mg+τ. ÝǾ٠ÐÇ Î ß α Mg à τ. Åß (3) à (4) Þ, Åß Á, ØÙ DSC Ç [7]. Henley [18], Q Ê τ Đß Æ Ëß ². Bergman [11], τ ¾ ÆÊ ÌÆ, Ú Ù bcc Æ. Wang [19], Mg Zn Al ¹Ç È ÑÍ ÌÆ, ± 2 Ʊ. Ç º, Æ Ëß ¼, ZA124 Ç Á ÌÆ¾Ú Å Æ ÐÆ È. Zhang [7] Đ Zn Á 14%, Al Á 2% 6% ZA ¹Ç ß Ò Ä Ã Î, ± Zn/Al Ç ³ ± Ä ², 4 ØÇ. Heat flow, mw 250 200 150 100 50 0 Phase transformation point I Phase transformation point II 0 100 200 300 400 500 600 700 Temperature, o C Æ 6 ZA124 Æ DSC Fig.6 DSC heating curves of ZA124 alloy

590 Ñ 45 µ Zhang, Zn/Al, Ë Ã ε Å. Sr ÉÆ, Ç ß, Sr Û À, Å Ô», à Zn à Al Ì Ôµ ¼, É Ó Zn/Al, ËÅà ε Å. É 2 ¾³, Á Sr ³¹ τ Î, ¾Ú Ù ÌÆ ÐÆ Æ, É É ±ÜÈ (Q) Ë (τ) Ä. Ca Sr ÇعÎ, Ç Â ϕ ½, ² Zhang, Ca Ø¹Ý ÃÓ Zn/Al Þ, É Ë Ã ϕ Å. 2 EDXS, Ca Ç (No.5 à No.6) ϕ Í Ca. ¾ ϕ Æ 152 Ì, Mg Ì 84, 68 Ê Zn à Al (Zn à Al Ì ) ² ÞÓÒ»Æ: K = nv/v (, n Ê Æ Ì ; v ÊÔ Ì ; V Æ ) à Mg, Al, Zn 4 ² Zn/Al ZA ºÈ Ó Å Ä ³ [7] Table 4 Second phase transformations and final intermetallic phases of ZA alloys with different Zn/Al ratio [7] Alloy Second phase Final intermetallic transformation phase ZA142 L α Mg+ε+τ ε, τ ZA144 L 1 α Mg+ϕ+L 2 τ L 2 +ϕ α Mg+τ+L 3 L 3 α Mg+τ ZA146 L 1 α Mg+ϕ+L 2 ϕ, τ L 2 +ϕ α Mg+τ Ì, ¾ÓÒÂ Þ (K) 73.7%. τ bcc Õ, Æ ÌÏ 162, Mg Ì 64, Ê Zn à Al, Þ K 78.3%. Ca Ì Mg, Mg Ì Al à Zn. Ca à Mg Ì, ØÙ³¹ Ca ¾Ú 2»Æ Mg Ì. ² ÞÃ Ì Î Àß º, Ca ϕ ³ÞÐ τ ³ Þ, ÝÇ, ÕÊ Ca عÁ Ø, Ñ ÛË ϕ Å, Ú τ Å. 3.2 Û 3 ØÇ Â ²¾Þ, عËÁ Sr ¾± ÞÐ Ç Ã ÉÚ, ع Sr Î. ZA ¹Ç È ³ ÐÞÃÌÉ [14], Sr عÎ, ÚÄ τ à ε, É ÃÈ ĐÇ ÉÚ. ² Ë Mg Zn «, ε Ê 330 350 Å. Wei [20] ¼Ú «: Mg 51 Zn 20 α Mg+MgZn, MgZn ²Õ, ĐÇ ÉÚ±.  ß, ± Ù ² «, ØÙ Ç Â Î MgZn, Ñ ÚĐ ÉÚ ±. Ca à Sr Çع, Ç Þ Ø, ¾Ú Ca ³¹ à ±ØÉ. Ç º ÉÚ Ç ±ØÉ, ÔµÝßÆ Sr à Ca ĐÇ, SEM ¾ Ã Ç Î. É Ç («7a) ¾Ù Â, Î ÆÈ Â ÃÎ Ç Æ 7 Æ µ Í SEM Fig.7 SEM micrographs of alloys No.1 (a), No.3 (b), No.5 (c) and No.6 (d) after creep test at 175 /70 MPa

Ñ 5 Å : Sr Á Ca Mg 12Zn 4Al 0.3Mn Å µá ÇØ 591, Ç, È Ì Ù Ç º, ÌÉ, [14] Ô. «7b ع 0.6%Sr Î Ç (No.3) Î. «¾Þ, Î Ù (τ ε)  ÃÉ Ç, ± Ö, Sr عÎÅ Ù º Ú. [20], ε ÔØ Þ (330 350 ) ¼ «. Ó Â Þ 175, ε «Þ, ¼  Æ, ß ¾Ú Ë ε «, ÝÇ ÃÇ ÉÚ. «7c ع Sr à Ca No.5 Ç Î. ÀÜ, Î ½ Å, Æ Ù ÁÇ Â, Ca عÙÎ ÃÇ ±ØÉ. Õ Ca Á Ø, No.6 Ç Å Ã ±ØÉ ½ ϕ («7d), Ú ÀРñØ, ¼ Õ, Ç Â Ç. 4 ß (1) Mg 12Zn 4Al 0.3Mn Ç ÀÜ α Mg à ÆÈ Q, Ú»Æ Ë «Mg 32 (Al, Zn) 49 (τ). (2) Sr عΠMg 12Zn 4Al 0.3Mn Ç, ÀÜ ÆÈ Ä Mg 32 (Al, Zn) 49 (τ),  à α Mg+Mg 51 Zn 20 (ε) ½. Ca Sr Ø¹Ç Î, ÀÜ Â Ã ±ØÉ α Mg+Al 2 Mg 5 Zn 2 (ϕ) ½, Ú Õ Ca ع Á Ø Ø. (3) Sr Ø ÃÇ Î Ã 200 Þ ¼ ÉÚ, º Þà ÞÕ Sr عÁ Ø ¾ ÎÝ É. Ca Sr ÇعÅÇ º Þ, ÞÏ. (4) Mg 12Zn 4Al 0.3Mn Ç Ü Ø Sr Ç º ÉÚ, Ca ÇعÎ, ÉÚ, Ca عÁÏ 0.4%, Ç À º ÉÚ. Đ [1] Luo A, Pekguleryuz M O. J Mater Sci, 1994; 29: 5259 [2] Li P J, Zeng D B, Guo X T. Chin Rare Earths, 2002; 23(2): 63 (Đ,, ÏÞ., 2002; 23(2): 63) [3] Luo A A. Int Mater Rev, 2004; 49: 13 [4] Zeng R C, Ke W, Xu Y B, Han E H, Zhu Z Y. Acta Metall Sin, 2001; 37: 673 ( ±,», Í, Ì, ÍĐ., 2001; 37: 673) [5] Zhang Z, Couture A, Luo A. Scr Mater, 1998; 39: 45 [6] Zhang J, Guo Z X, Pan F S, Li Z S, Luo X D. Mater Sci Eng, 2007; A456: 43 [7] Zhang Z, Tremblay R. Canad Metall Quart, 2000; 39: 503 [8] Zhang Z, Tremblay R, Dubé D. Mater Sci Eng, 2004; A385: 286 [9] Liu C M, Zhu X R, Zhou H T. Magnesium Phase Diagram. Changsha: Central South University Press, 2006: 256 (ÊÄ, ̱, Þ. Æ Å. ¾: Ô Á, 2006: 256) [10] Higashi I, Shiotani N, Uda M, Mizoguchi T, Katoh H. J Solid State Chem, 1981; 36: 225 [11] Bergman G, Waugh J L T, Pauling L. Acta Crystal Logr, 1957; 10: 254 [12] Bourgeois L, Muddle B C, Nie J F. Acta Mater, 2001; 49: 2701 [13] Sun Y S, Zhang W M, Min X G. Acta Metall, 2001; 14: 330 [14] Vogel M, Kraft O, Dehm G, Arzt E. Scr Mater, 2001; 45: 517 [15] Takeuchi T, Murasaki S, Matsumuro A, Mizutani U. J Non Cryst Solids, 1993; 914: 156 [16] Niikura A, Tsai A, Nishiyama N, Inoue A, Masumoto T. Mater Sci Eng, 1994; A1387: 181 [17] Petrov D V, Petzow G, Effenberg G. Aluminum Magnesium Zinc Ternary Alloys: A Comprehensive Compendium of Evaluated Constitutional Data and Phase Diagrams. Weinheim: VCM, 1993: 57 [18] Henley C L, Elser V. Philos Mag, 1986; 53B: 59 [19] Wang S Q, Ye H Q. Philos Mag, 1991; 64B: 551 [20] Wei L Y, Dunlop G L, Westengen H. Metall Mater Trans, 1995; 26A: 1947