Effects of Al content on hardness, lattice parameter and microstructure of Ti1-xAlxN films

Ti1-xAlxN films were synthesized by the are ion plating method using Ti1-xAlx alloy targets with differing Al contents. X-ray diffraction patterns from films indicated that the NaCl structure for x less than or equal to 0.6 changed into wurtzite structure for x greater than or equal to 0.7. For films with x less than or equal to 0.6, the lattice parameter decreased in proportion to the x value, and correspondingly, the hardness gradually increased from similar to 2000 HV for x=0 up to 3200 HV for x=0.6. On the other hand. the hardness of films with x greater than or equal to 0.7 abruptly deceased from similar to 3000 HV for x=0.7 to 1400 HV for x=1. Further, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed that the films with x=0.6 had a typical columnar structure with grain sizes of 100-200 nm. While for films with x greater than or equal to 0.7, a columnar structure disappeared and excess Al atoms did not segregate at the grain boundaries as AIN, but Ti and Al were uniformly dissolved and distributed as nitride grains with wurtzite structure. (C) 1999 Elsevier Science S.A. All rights reserved.