Effect of dimensionless heat input during laser solid forming of high-strength steel

Laser solid forming(LSF)technology can be used to rapidly manufacture and repair high-strength steel parts with superior performance,but the value of the heat input during operation is difficult to quantify,which has a substantial impact on the microstructure and mechanical properties of the parts.A promising method to improve the forming efficiency and quality of LSFed parts is to accurately control the heat input and explore its relationship with the microstructure and mechanical properties.To remove the interference of other variables from the experiment,the dimensionless heat input Q;^(∗)was introduced.The Q^(∗)values were designed in advance to calculate the experimental parameters used to perform the LSF experiment.The microstructure was observed at different regions of the sample,and its mechanical properties were analyzed.From the results,the following conclusions were drawn.The Q;^(∗)value was directly related to the cooling rate and heat accumulation in the top structure,leading to the formation of different microstructures;it also modified the original structure at the bottom,affecting the subsequent thermal cycle and indirectly changing the tempered martensite morphology.The heat input also affected the mechanical properties of the sample.The hardness of the stable zone decreased with increasing Q;^(∗)value,and the lowest value was 190 HV.Similarly,the tensile strength and yield strength of the LSFed samples decreased considerably with increasing Q;^(∗)value,and the lowest values were 735 and 604 MPa,respectively.Only the elongation and reduction in the area increased after a slight decrease.The Q;^(∗)value had a significant effect on heat treatment.When Q;^(∗)=2.9,the increase in tensile strength and yield strength after heat treatment was the largest(29%and 44%,respectively).

Controlling solid form and crystal habit of triphenylmethanol by antisolvent crystallization in a microfluidic device

Crystal habit and crystal form are critical elements in determining product properties and functions. In this work, we developed a microfluidic antisolvent crystallization technique to rapidly screen and accurately control the solid form and crystal habit of triphenylmethanol(Ph_(3)COH). This advanced technique separates the primary mixing of solutions from crystal formation(nucleation and growth) by introducing the microfluidic device, avoiding clogging in microchannels to obtain high-quality crystals. The results show that we can achieve controllable preparation of pure 2Ph_(3)COH·DMSO(DMSO solvate), pure Ph_(3)COH(form β), and mixed crystals with different mass ratios. Moreover, the microscale can prompt the DMSO solvate to grow into hexagonal sheet-like and bulk crystals. We can regulate the aspect ratio of hexagonal sheet-like crystals in binary solvents and control the crystal habit of the form β to transition between long needle-like shapes and short hexagonal prisms in DMF-H_(2)O. Meanwhile, we revealed that the solvent ratio, the antisolvent flow rate, and the initial concentration of Ph_(3)COH are the main factors affecting the solid form selectivity and morphology transition. Such a novel method would be considered as a promising technique to be extended to screen and control key crystallization parameters of other substances.

Calculation on the Solid Solution Forming Enthalpies of Re-Mo-Ti Gradient Alloy in Thermodynamics

The idea about preparation of Re-Mo-Ti alloy is put forward because of applications of Re and Mo-Re alloys in aerospace.Basing on the thermodynamics theory,the feasibility of developing a new high temperature alloy Re-Mo-Ti is investigated.The solid solution forming enthalpies of binary alloys Re-Ti,Mo-Ti and Mo-Re are calculated with the Miedema thermodynamics theory.The Miedema theory of binary alloy can be used in ternary alloy through Kohler model or Toop model.The calculated results show that the forming enthalpies of binary alloys Re-Ti,Ti-Mo and Re-Mo are negative,which indicates that binary alloys Re-Ti,Ti-Mo and Re-Mo can form solid solution in wider component area.The forming enthalpies of Re-Mo-Ti ternary alloy are still negative and smaller than those of binary alloys Re-Ti,Ti-Mo or Re-Mo,which indicates it is possible to form large solid solution graph area among ternary alloys of Ti,Mo,Re elements.It is feasible to develop a new high temperature material in thermodynamics,in this material Re-Mo-Ti solid solution as base phase,and the Ti5Re24 intermetallic compounds or interphase ω (Ti4Mo3) as strengthening phase.

Hot deformation behavior and microstructure evolution of the laser solid formed TC4 titanium alloy

Hot compressive experiments of the laser solid formed(LSFed)TC4 titanium alloy were conducted at a wide temperature range of 650-950℃and strain rate of 0.01-10 s^(-1).The Arrheniustype constitutive models of the LSFed TC4 alloy were established at the temperature range of 800-950℃and of 650-800℃,respectively.The average relative error between the predicted stresses and experimental values in those two temperature ranges are 10.4%and 8.3%,respectively,indicating that the prediction models constructed in this paper are in a good agreement with experimental data.Processing maps were established by the principle of dynamic materials modeling on the basis of the data achieved from the hot compression experiments.The processing parameters corresponding to the stable and unstable regions of material deformation can be determined from the processing maps.The microstructure evolution of the stable and unstable regions of the samples after tests were observed.Finally,the effect of hot compressive parameters on the microstructure were investigated to research the dynamic recrystallization and the texture of the deformed LSFed TC4 alloy.

Pharmaceutical cocrystals: A review of preparations, physicochemical properties and applications

Pharmaceutical cocrystals are multicomponent systems in which at least one component is an active pharmaceutical ingredient and the others are pharmaceutically acceptable ingredients.Cocrystallization of a drug substance with a coformer is a promising and emerging approach to improve the performance of pharmaceuticals,such as solubility,dissolution profile,pharmacokinetics and stability.This review article presents a comprehensive overview of pharmaceutical cocrystals,including preparation methods,physicochemical properties,and applications.Furthermore,some examples of drug cocrystals are highlighted to illustrate the effect of crystal structures on the various aspects of active pharmaceutical ingredients,such as physical stability,chemical stability,mechanical properties,optical properties,bioavailability,sustained release and therapeutic effect.This review will provide guidance for more efficient design and manufacture of pharmaceutical cocrystals with desired physicochemical properties and applications.