Wear-resistant boride composites with high percentage of reinforcement phase
A highly wear resistant sintered, hot pressed, or otherwise compacted ceramic composite material is described, consisting of two discrete phases of the form AlxMgyB14 where x and y ≦1 or like hard, orthorhombic compounds, and TiB2 or like Group IVB transition metal di-borides, and with an unexpectedly high contentof transition metal di-boride in the range from 40 to 90 percent (28 to 85 volume percent).
In situ reacted TiB2-reinforced mullite
In situ formation of TiB2 in mullite matrix through the reaction of TiO2, boron and carbon has been studied. In hot-pressed and pressureless-sintered samples, in addition to TiB2, TiC was also found to be dispersed phases in mullite matrix. However, in the case of pressurelesssintered samples, mullite/TiB2 composite with 98% relative density can be obtained through a preheating step held at 1300 °C for longer than 3 h and then sintering at a temperature above 1600 °C. Hot-pressed composite containing 30 vol% TiB2 gives a flexural strength of 427 MPa and a fracture toughness of 4.3 MPam1/2. Pressureless-sintered composite containing 20 vol% TiB2 gives a flexural strength of 384 MPa and a fracture toughness of 3.87 MPam1/2.
Description of roughness profiles by separating the random and periodic components
Abstract The probability that it is not possible to obtain a significant description of roughness profiles composed of random and periodic components by using statistical methods is discussed. It is shown that the random and periodic components can be separated by using the frequency spectrum and the autocorrelation function of the profile. The physical significance of the separate components is discussed and it is shown that it is possible to describe a long crested surface by a single profile using these components The method of separating the random and periodic components allows a parametrical description of the roughness profile to be given. It is then possible to use these parameters to calculate a synthetic signal sign with the same basic properties as the measured profile.