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WCoB based cermets were prepared by spark plasma sintering at sintering temperature among 600°C-1200 °C. The phase evolution was investigated by detecting density behavior, phase composition, microstructure and mechanical properties during sintering process. The sintering process can be divided into three stages: powder densification, solid phase reaction and liquid phase sintering. WCoB hard phase forms at 1000 °C during solid phase sintering, showing better mechanical properties than Co 2 B, especially on Vicker's hardness. WCoB hard phase forms on the basis of Co 2 B binary boride and its content increases in liquid phase sintering stage with high density. The Vicker's hardness and transverse rupture strength (TRS) reach the maximum value of 1262 Hv and 1212 MPa at 1200 °C and 1170 °C, respectively. The fracture toughness reaches the maximum value of 21.8 MPa m1/2 at 1050 °C, and the inter-granular fracture is the main fracture mechanism. [ABSTRACT FROM AUTHOR]

The study investigated the effect of nickel content on the microstructure and mechanical properties of Cu–12Al-xNi alloys prepared using powder metallurgy. The results indicated that the alloys investigated consisted of α-Cu and γ 2 (Al 4 Cu 9), containing less than 4 wt% Ni content. The α-Cu phase gradually increased, while the γ 2 (Al 4 Cu 9) phase gradually decreased as the sintering temperature increased. Both the strength and hardness of the alloy thus reduced. When the Ni content increased above 4 wt%, the NiAl phase precipitated at the grain boundaries, which resulted in an increase in the strength of the alloy. Additionally, the tensile strength reached a maximum of 390 MPa when the Ni content reached 6 wt%. The decrease in the tensile strength for higher Ni content was attributed to the formation of a NiAl phase network. And the addition of nickel did not significantly alter the sintering density of the alloy. The mechanisms of microstructure evolution and strengthening mechanisms were investigated and discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The mechanical properties of powder metallurgy (PM) materials are closely related to their density. In this case we demonstrate an approach of utilizing machine-learning algorithms trained on experimental data to predict the sintered density of PM materials. Descriptors were selected from the features including processing parameters, chemical composition, property of raw materials and so on. And the training data are collected by the experimental setup in our lab and the literatures on five kinds of P/M alloys. The multilayer perceptron model (MLP) outperformed other four regression and neutral network models with high coefficient of correlation and low error. The sintered density predicted by MLP model agreed well with the experimental data with a tolerable error less than 0.028, which confirms its capability over P/M materials design procedures. Then the obtained MLP model is used for Cu-9Al P/M alloy to guide selecting the processing parameters to reach the expected sintered density of 0.88. The Cu-9Al powders were fabricated with the predicted parameters including the specific shape factor, particle size, pressing pressure and sintering temperature, and the obtained relative sintered density is 0.885. [ABSTRACT FROM AUTHOR]

Owing to its excellent wear resistance and good mechanical properties, the sintered Cu–Al–Ni alloy is an ideal material for preparing sliding bearings and self-lubricating sleeves. Adding trace elements into the Cu–Al–Ni alloy is expected to further enhance these properties. Hence, in this work, the microstructure and properties of sintered Cu-12 Al-6 Ni alloys with varying contents of added Ti are studied. Results indicated that the NiAl, γ 2 , and α phases were distinctly refined when the Ti addition was 0.2 wt%, and a small amount of the granular X phase ((Cu, Ni) 2 AlTi) appeared in the alloy. The X phase increased and coarsened with increasing Ti addition. When the Ti addition was 0.7 wt%, pores appeared in the center of the large granular X phase. With increasing Ti addition, the sintered density of the alloys gradually decreased, while the hardness and tensile strength increased first and then decreased. When the Ti addition was 0.7 wt%, the hardness reached the maximum (160 HB), while when the Ti addition was 0.2 wt%, the tensile strength reached the maximum (412.2 MPa). Moreover, the friction coefficient and wear loss of the alloy were the lowest when the Ti addition was 0.2 wt%. These findings can provide some theoretical guidance for fabricating high-performance Cu–Al–Ni powder alloys. [ABSTRACT FROM AUTHOR]

In this research, the effects of the compaction velocity on the sinterability of the Al–Fe–Cr–Ti powder metallurgy (PM) alloy by high velocity compaction were investigated. The Al–Fe–Cr–Ti alloy powder was compacted with different velocities by high velocity compaction and then sintered under a flow of high pure (99.999 wt%) nitrogen gas. Results indicated that both the sintered density and mechanical properties increased with increasing compaction velocity. By increasing the compaction velocity, the shrinkage of the sintered samples decreased. A maximum sintered density of 2.85 gcm−3 (relative density is 98%) was obtained when the compaction velocity was 9.4 ms−1. The radial and axial shrinkage were controlled to less than 1% at a compaction velocity of 9.4 ms−1. At a compaction velocity of 9.4 ms−1, sintered compacts with an ultimate tensile strength of 222 MPa and a yield strength of 160 MPa were achieved. The maximum elongation was observed to be 2.6%. The enhanced tensile properties of the Al–Fe–Cr–Ti alloy were mainly due to particle boundary strengthening. [ABSTRACT FROM AUTHOR]

In this study, the powder metallurgy process was used to prepare friction materials. Fe and graphite powders were added to the friction materials at different proportions. The friction and wear properties of the materials were evaluated by the MM3000 friction and wear tester. Combined with scanning electron microscope and physical and mechanical properties testing, the influence of the synergistic effect of Fe powder and graphite on the properties of the friction materials was studied. The results showed that the total content of Fe and graphite has not changed. Moreover, the hardness and strength of the material increased by increasing the iron content. The average friction coefficient first increased and then decreased. Furthermore, the instantaneous friction coefficient stability decreased, and the wear extent first slightly decreased and then increased. The comprehensive properties of the material were optimal when the Fe content and graphite powder were 14 % and 20 %, respectively. [ABSTRACT FROM AUTHOR]