Hardening (metallurgy)

About: Hardening (metallurgy) is a research topic. Over the lifetime, 25584 publications have been published within this topic receiving 376012 citations.

Particle reinforcement of ductile matrices against plastic flow and creep

Abstract: A theoretical investigation is made of the role of non-deforming particles in reinforcing ductile matrix materials against plastic flow and creep. The study is carried out within the framework of continuum plasticity theory using cell models to implement most of the calculations. Systematic results are given for the influence of particle volume fraction and shape on the overall behavior of composites with uniformly distributed, aligned reinforcement. The stress-strain behavior of the matrix material is characterized by elastic-perfectly plastic behavior or by power-law hardening behavior of the Ramberg-Osgood type. A relatively simple connection is noted between the asymptotic reference stress for the composite with the power-law hardening matrix and the limit flow stress of the corresponding composite with the elastic-perfectly plastic matrix. The asymptotic reference stress for the composite with the power-law matrix is applicable to steady-state creep. A limited study is reported on the overall limit flow stress for composites with randomly orientated disc-like or needle-like particles when the particles are arranged in a packet-like morphology.

Mechanical properties and machining performance of Ti1−xAlxN-coated cutting tools

Abstract: The mechanical properties and machining performance of Ti 1− x Al x N-coated cutting tools have been investigated. Processing by arc evaporation using cathodes with a range of compositions was performed to obtain coatings with compositions x =0, x =0.25, x =0.33, x =0.50, x =0.66 and x =0.74. As-deposited coatings with x ≤0.66 had metastable cubic structures, whereas x =0.74 yielded two-phase coatings consisting of cubic and hexagonal structures. The as-deposited and isothermally annealed coatings were characterised by nanoindentation, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Cutting tests revealing tool wear mechanisms were also performed. Results show that the Al content, x , promotes a (200) preferred crystallographic orientation and has a large influence on the hardness of as-deposited coatings. The high hardness (∼37 GPa) and texture of the as-deposited Ti 1− x Al x N coatings are retained for annealing temperatures up to 950 °C, which indicates a superior stability of this system compared to TiN and Ti(C,N) coatings. We propose that competing mechanisms are responsible for the effectively constant hardness: softening by residual stress relaxation through lattice defect annihilation is balanced by hardening from formation of a coherent nanocomposite structure of c-TiN and c-AlN domains by spinodal decomposition. This example of secondary-phase transformation (age-) hardening is proposed as a new route for advanced surface engineering, and for the development of future generation hard coatings.