Three groups of GCr15 steel were heat-treated respectively by conventional spheroidizing annealing, circulation spheroidizing annealing, 1050°C for 30min oil cooling quenching + 700°C tempering. The final heat treatment of these GCr15 steel was 840°C oil cooling quenching + 150°C tempering. The microstructure of the heat-treated GCr15 were observed and the mechanism of three spheroidizing treatment were discussed in this paper. The results showed that: There is obvious difference among the three groups carbide of GCr15 for the mechanism of three spheroidizing treatments is different. The GCr15 has 1050°C for 30min oil cooling quenching + 700°C tempering showed the best result of carbide spheroidizing. The microstructure of GCr15 after 840°C oil cooling quenching + 150 °C tempering was tempered martensite and carbide which is fine, round and widely distributed.
Nanostructured Cu90Al10 alloy powders were prepared by high energy ball milling mechanical alloying (MA). Up to 10 at.% Al could be dissolved into copper by mechanical alloying at room temperature. Effects of milling time on phase transformation, structural characteristics, and mechanical property of powders were investigated by using X-ray diffraction (XRD), Optical Microscopy (OM) and microhardness tester. The results show: with increasing the milling time, the powder particle size increased gradually, and then it tended to be homogeneous. The grain size of the alloy decreased gradually, but the yield strength increased with the extension of the ball milling. After 30h milling, the grain size reached the minimum value of 9 nm, and the yield strength obtained the maximum value of 511 MPa.
The W-Ti-Co powders was doped different content of TaC with an average particle size of 270nm were prepared by 72 hours high-energy ball milling. The powder was cold isostatic pressed and vacuum sintered at 1380°C. The physical properties and the micrographs of samples were detected. The main conclusions were as follow: the density and Cobalt magnetic decreased with the content of TaC increasing, the coercivity increased at first and then decreased, the coercivity of alloy with 0.6wt.% TaC was higher than the other. When the content of TaC was less than 0.6wt.%, the hardness increased with the content of TaC increasing .While when the content of TaC was more than 0.6wt.%, the hardness decreased obviously. Comparing with the alloy without TaC doped, the transverse rupture strength (TRS) of the alloy with 0.4wt.%TaC increased to a larger extent. When the content of TaC was more than 0.4wt.%, the transverse rupture strength (TRS) decreased with the content of TaC increasing. The TaC could inhibit the grain growth, and the comprehensive performance of the alloy with 0.4wt.% TaC was best.
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