546 H.-S.Chu et al./Scripta Materialia 45 (2001)541-546 thermograms reveal that the formations of the B"zone and B'phase of the composites are depressed,because of the loss of the precipitation hardening element,Mg,reacting with the Al2O3 particles to yield MgAl2O4.The large work-hardening capacity of the composites is attributed to the high plastic incompatibility between Al2O3 and the matrix.The composites exhibit excellent ductility,probably due to the full density and the uniform dispersion of Al2O3 particles caused by the mechanical kneading of re- ciprocating extrusion. References [1]Fishman,S.G.(1986).J Metal 38,26. [2]Nair,S.V.,Tien,J.K..Bates,R.C.(1985).Int Mater Rev 30,275. [3]Webster,D.(1982).Metall Trans A 13A,1511. [4]Lewandowski,J.J.,Liu,C.Hunt,W.H.(1989).Mater Sci Eng A 107,241. [5]Lloyd,D.J.(1991).Acta Metall et Mater 39.59. [6]Arsenault,R.J.,Shi,N.(1986).Mater Sci Eng A 81,175. [7]Barlow,C.Y.,Hansen,N.(1991).Acta Metall et Mater 39,1971. [8]House,M.B.,Meinert,K.C.,Bhagat,R.B.(1991).J Metal 43.24. [9]Chu,H.S.,Liu,K.S.,Yeh,J.W.(2000).Metall Trans A 31A,2587. [10]Dulta,I.,Allen,S.M.(1991).J Mater Sci Lett 10.323. [11]Dulta,I.,Allen,S.M.,Halfey,J.L.(1991).Metall Trans A 22A,2553. [12]McKimpson,M.G.,Scott,T.E.(1989).Mater Sci Eng A 107,93. [13]Lloyd,D.J.(1994).Int Mater Rev 39,1.           9           #             # +#   /  
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