Bending strength of an Al-Al3Ni functionally graded material

The gradient of bending strength of an Al-Al3Ni functionally graded material (FGM) has been examined using 3-point bending tests. Specimens with rectangular cross-sections of 6 x 6 mm(2) were machined from a thick-walled FGM tube such that the thickness direction of the specimen coincided with the radial direction of the tube. Thus the specimens had a graded composition of the Al3Ni phase in the thickness direction. Four types of specimens characterized by four nominal volume fractions of the Al3Ni phase at the crack initiation plane, namely V-f = 0, 24, 49 and 53 vol%, were employed in the study. Fracture surfaces consisted of cleavage facets of the Al3Ni phase surrounded by dimples of the aluminum phase. Brittle fracture of Al3Ni dominated the fracture process of Al-Al-3 Ni FGM. Fracture strengths of the four types of specimens were plotted on the standard normal and Weibull probability paper. The trends of each data set exhibited good linearity, making it difficult to determine the differences in the fit between the two kinds of probability papers. Maximum average fracture stress of 156 MPa was obtained from the V-f = 24 vol% specimen, and decreased in the following order with specimen type: V-f = 24, 49, 53 and 0 vol%. Fracture strength of Al-Al3Ni FGM attained a maximum value of 160 MPa at V-f x 10 vol% and decreased with an increase in the Al3Ni volume fraction due to the size effect that controls the strength of the brittle Al3Ni phase. (C) 1997 Elsevier Science Limited. All rights reserved.