جستجوی مقالات مرتبط با کلیدواژه "in-situ method" در نشریات گروه "مواد و متالورژی"

Al-Al3Ni composites due to their high strength, creep resistance, fatigue resistance, good ductility, adequate toughness, high corrosion resistance and hardness have gained considerable attention in recent years. In the present investigation, powder metallurgy (PM) method was used to in-situ produce Al-Al3Ni composites. Commercially pure aluminum powders (63-125 μm) and the same sized pure nickel powders used as starting materials. The Al/Ni powder mixtures with different Ni contents subjected to cold pressing and then sintering at different temperatures for various times. Samples of Al powders without Ni addition were also prepared using identical procedures as for Al/Ni composites to serve as the reference samples. In order to increase effectiveness of interaction between Al and Ni during sintering, Ni powders subjected to high-energy ball milling. The increased milling time of Ni particles from 1.5h to 6h resulted in progressive reaction between Ni flakes and spherical Al particles presented in Al-20wt.% Ni samples which was sintered at 655˚C for 15min. This was accompanied by the increased content of hard Al3Ni phase and thereby continuous increased hardness of composites. The XRD results confirmed that sintering at 655˚C of the Al/Ni powder compact containing 15wt.% of ball-milled Ni resulted in complete reaction and Al-Al3Ni eutectic formed without any unreacted Ni. The porosity level of the samples increased with increasing percentage of Al3Ni phase in the matrix. Brinell hardness values of all the composite samples were higher than that of their reference counterpart. The Al-20wt.% Ni sample prepared by milled Ni exhibited the maximum hardness value being almost three times of that of the reference sample. However, the increased content of milled Ni to 25wt.% resulted in some unreacted Ni particles in the matrix as was confirmed by XRD studies.