Graded Materials of (TiB_2)_pNi with Nickel Substrate Prepared by Field-Activated Pressure-Assisted Synthesis Process

The preparation of functionally graded materials （FGMs） of （TiB2）pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process （FAPAS） was investigated. Ni3Al was chosen as a layer of FGM for the first time due to its great deal of heat released during its synthesis from nickel and aluminium powder. The microstructure, phase composition of layers, micro-hardness and elemental concentration profiles across interfaces were characterized. The significant inter-diffusion of elements between layers showed the formation of good bonds. The measured micro-hardness values of the sample increased monotonically to more than 3 500 HK over a distance of 2 mm from the nickel substrate to the surface layer （TiB2）pNi. The results of this investigation demonstrate the feasibility of the FAPAS process for rapid formation of FGMs with good diffusion bonds.

Structural Characterization of AlMgB_(14) Prepared by Field-activated, Pressure-assisted Synthesis

Mechanical alloying （MA） and field-activated, pressure-assisted synthesis （FAPAS） were used for the in situ synthesis and densification of ultra-hard, super-abrasive AIMgB14 metallic ceramic, performed at 1500 ℃ under a pressure of 60 MPa with the elemental constituents of aluminum, magnesium, and boron. The microstructure and components of synthesized metallic ceramic were observed and determined by scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDX）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The results showed that the main components of the samples were AIMgB14 with a few MgAI204.MgAI204 was derived from the contamination of the preliminary powders and the milling process. The average hardness of the samples that provided the results was 26.1 GPa. The average density of the samples was 2.62 g/cm^3, which is 98% of its theoretical density. The sample of AIMgB14-TiB2 composite with 30 wt% TiB2 had a hardness of 29.5 GPa, which is consistent with that of AIMgB14-TiB2 composite with 30 wt% TiB2 prepared by mechanical alloying/hot uniaxial pressing. Thus, a new approach was developed using the mechanical alloying and FAPAS process to synthesize AIMgB14 with fast heating, high efficiency, energy saving, and high yield.

Preparation and scratch test of AlMgB_(14) modified by TiB_2

In this paper, the Al Mg B14 and Al Mg B14–Ti B2 composites were synthesized by means of mechanical alloying and the field-activated and pressure-assisted synthesis process. The effect of temperature and pressure on the purity and property of products was discussed. The results show that the process of preparing Al Mg B14 bulk materials is optimized as follows： synthesis temperature1,400–1,500 ℃, heating rate 100 ℃ min^-1, axial pressure60 MPa, heat preservation 8–10 min, optimum starting powders＇ ratio Al： Mg： B = 0.1915：0.1363：0.6722, and adding excessive 3 wt% Al. The abrasion resistance of Al Mg B14 composites with varying amounts of Ti B2 was studied using single-point diamond scratch tests with loads ranging from 10 to 100 N in 10 N increments. The scratch width increases almost linearly with the applied load and decreases with Ti B2 proportion increasing up to 70 wt%.With its advantages of fast heating, short reaction time,energy conservation, and high purity, this method offers a new way to synthesize Al Mg B14 and Al Mg B14–Ti B2 composites.