Aging Precipitation Behavior Research Articles

HREM Observation of Age-Precipitated Particles in Practical Cu-bearing Ultra-Low Carbon Steels

Morphology, distribution and crystal structures of age-precipitated particles in practical Cu-bearing steels with ultra-low carbon were studied by high resolution electron microscopy (HREM). The age-precipitation behavior was explored when poly-microalloying elements Cu, Nb, Cr, Mo and Ni were used and ɛ-Cu particles coexisted with carbides (carbonitrides) in steels. The fine dispersed ɛ-Cu particles and carbides of microalloying element Nb, Cr, Mo being about 10 nm only in size were observed in peak aging specimens and over-aging specimens. The twin structures and stacking faults in the particles and the transient structures formed in the early stage of the particle precipitation were also observed. The crystal structure of three types of age-precipitation particles was firstly identified by lattice streaks in HREM images of the single particles. The experimental method identifying crystal structure of fine and dispersed particles using HREM images of single particle was proposed.

Influence of Indium Trace Addition on the Precipitation Behavior in a 357 Cast Aluminum Alloy

Effect of indium addition on aging precipitation behavior of 357 cast alloy has been investigated by hardness measurement, differential scanning calorimetry (DSC) and TEM analysis. Age hardening results show that 0.1 wt.% indium addition to 357 cast alloy increases the peak hardness by 20 HV during aging at 160 °C. DSC and TEM analysis results show that indium addition constrains precipitation of GP zones, and enhances precipitation of phases. The possible indium atoms participating in the precipitation during aging and the large indium-vacancy binding energy can explain the effect of indium on aging behavior of 357 cast alloy.

Aging Precipitation Behavior of Cu-Ag-Cr Alloy

The Cu-Ag-Cr alloy is a kind of aging hardening copper alloy and has excellent combination properties of high strength and good electrical and thermal conductivity. In the present investigation, the aging precipitation behavior of Cu-Ag-Cr alloy is studied, and the effects of aging processes on the microstructure and properties are discussed. Emphasis is on the correlation between the coherency and coarsening behavior of the Cr precipitates. When the alloy aging at low annealing temperatures, the homogeneous dispersed Cr precipitates are observed to be approximately spherical and keep coherent with Cu matrix in the Cu-Ag-Cr alloy, the coherency is lost between at 450°C~520°C, coherency on coarsening process of Cr precipitates at high annealing temperatures, the radium for coherent / semi-coherent transition of the Cr precipitates is determined from TEM micrographs as 15-45nm. Aging in the intermediate stage, coherent and semi-coherent particles can co-exist(15<r<45nm). The precipitation can be accelerated by cold deformation before aging, the 60% deformed Cu-Ag-Cr alloy aging at 480°C for 1h, the hardness and electrical conductivity can respectively reach to 158HV and 85%IACS.

The Aging Behavior for Low Carbon Bainitic Steel Bearing Cu-Nb

By the aid of optical microscope, Hardness measurement, SEM, TEM and the chemical quantitative phase analysis technique, the influence of copper, niobium, and chromium on the aging hardness has been investigated. The aging precipitation behavior and the interaction between various precipitates have also been discussed. The results indicate that since there are multi aging-hardening elements in the steel the aging hardening behaviors are complicated. During the aging the ε－copper， and carbides containing iron and chromium will precipitate. Also, new niobium carbonitride precipitation occurs. These precipitation processes cause marked hardening effect and various hardness peaks. The ε－copper can precipitate at dislocation and lath boundaries preferentially. During the aging the bainite lath united and became wider and then gradually vanished.

Effect of Mg on age hardening and precipitation behavior of an AlSiCuMg cast alloy

Effect of Mg on age hardening and precipitation behavior of an AlSiCuMg cast alloy

Strain aging precipitation behavior of β phase in W-Ni-Fe ternary system

Strain aging precipitation behavior of β phase in W-Ni-Fe ternary system

Aging behaviors of alumina borate whisker reinforced AC8A-AI composite

The aging behavior of alumina borate whisker (Al18B4O33w/AC8A-Al) composite was examined by hardness and differential scanning calorimetry heat flow measurement. Microstructures were investigated by transmission electronic microscope. The results indicated that the interfacial reaction played an important role in the aging precipitation behavior of the composite. As the interfacial reaction between the whiskers and AC8A-Al alloy consumed the Mg atom of the matrix in the composite, the time to the peak aging of the composite was almost same as that of the AC8A-Al alloy. The free precipitation zone can be found nearby some whisker in the composite, duo to Mg content decreased in the matrix.