Macroscopic kinetics of discontinuous precipitation in a Mg-8.5 wt% Al alloy

Modeling the precipitation processes and strengthening mechanisms in a Mg-Al-(Zn) AZ91 alloy

“…The activation energy for this diffusion is usually found to be ϳ0.5 of that for bulk diffusion, and as a result, discontinuous precipitation is often found to destabilize microstructures at low temperatures. The morphology, [5,6] crystallography, [6,12] and kinetics [5,[14][15][16][17] of the growing lamellar aggregate as well as the solute redistribution accompanying growth [15,18,19] have all been thoroughly investigated and the general theory of growth [20][21][22][23][24][25] is now relatively well understood.…”

Influence of a strong static magnetic field on the discontinuous precipitation reaction in Mg–9Al–1Zn alloy

“…The values of v and I s thus obtained should be I s = a πd 2 and v = 3ad 8b The above theory was proved to be suitable in describing DP reaction without the influence of concurrently occurring continuous precipitation [20]. In the present study, as after 4 h, discontinuous precipitation was greatly affected by continuous precipitation, therefore, only the data of the initial 4 h were analyzed with the above equations.…”

“…According to the theory of Johnson and Mehl [19], the macroscopic kinetic law for the transformation of discontinuous precipitation may be approximated by [20]: where X is the volume fraction of transformed DP zone, t an annealing time, K a function of I s (nucleation rate per unit time and unit surface of boundary), v (the average velocity of the RF) and d (average grain size). K is given by…”

Aging Behaviors in AZ91D/Al<SUB>18</SUB>B<SUB>4</SUB>O<SUB>33w</SUB> Composite Fabricated by Squeeze Casting

“…13,14) However, independent of the exact mechanisms, both the mechanisms require the migrations of grain boundary to serve as a reaction front, the movability of the grain boundaries being a crucial factor for the nucleation and growth of discontinuous precipitation. 12,14) In AZ91D/ABO w composite, the grain boundaries are bounded by the ABO w and have limited movability. It is disadvantage for discontinuous precipitation.…”

“…[2][3][4][5][6][7][8] Mg-Al binary alloys and Mg-Al-Zn ternary alloys having good castability and mechanical strength are attractive. 3,[8][9][10] Many studies [9][10][11][12][13][14][15][16][17] on the aging behaviors of Mg-Al-based alloy have shown that the precipitates form either continuously or discontinuously, and continuous precipitate is responsible for most of the age-hardening in Mg-Al-based alloys.…”