Effects of process parameters on the microstructure during the hot compression of a TC6 titanium alloy

The effects of process parameters on the microstructural evolution, includinggrain size and volume traction of the a phase during hot forming of a TC6 alloy were investigatedusing compression tests. Experiments were conducted on the material with (α + β) phases atdeformation temperatures of 800, 860, 920, and 950℃, strain rates of 0.001, 0.01, 1, and 50 s^(-1),and height direction reductions of 30%, 40%, and 50%. After reaching a peak value near 920℃, thegrain size and volume fraction decrease with further increase of deformation temperature. The strainrate affects the morphologies and grain size of α phase of the TC6 titanium alloy. At a lowerstrain rate, the effect of the strain rate on the volume fraction is greater than that at a higherstrain rate under the experimental conditions. The effects of the strain rate on the microstructurealso result from deformation heating. The grain size of the α phase increases with an increase inheight direction reduction after an early drop. The effect of height direction reduction on thevolume fraction is similar to that of the grain size. All of the optical micrographs andquantitative metallography show that deformation process parameters affect the microstructure duringhot forming of the TC6 alloy, and a correlation between the temperature, strain, and strain rateappears to be a significant fuzzy characteristic.

Wire-feed laser additive manufacturing of dissimilar metals via dual molten pool interface interlocking mechanism

Intermetallic compounds produced in laser additive manufacturing are the main factors restricting the joint performance of dissimilar metals.To solve this problem,a dual molten pool interface interlocking mechanism was proposed in this study.Based on a dual molten pool interface interlocking mechanism,the dissimilar metals,aluminum alloy and stainless steel,were produced as single-layer and multilayer samples,using the wire-feed laser additive manufacturing directed energy deposition technology.The preferred parameters for the dual molten pool interface interlocking mechanism process of the dissimilar metals,aluminum alloy and stainless steel,were obtained.The matching relationship between the interface connection of dissimilar metals and the process parameters was established.The results demonstrated excellent mechanical occlusion at the connection interface and no apparent intermetallic compound layer.Good feature size and high microhardness were observed under a laser power of 660 W,a wire feeding speed of 55 mm/s,and a platform moving speed of 10 mm/s.Molecular dynamics simulations demonstrated a faster rate of aluminum diffusion in the aluminum alloy substrate to stainless steel under the action of the initial contact force than without the initial contact force.Thus,the dual molten pool interface interlocking mechanism can effectively reduce the intermetallic compound layer when dissimilar metals are connected in the aerospace field.

Optimization of fused deposition modeling process parameters:a review of current research and future prospects

Fused deposition modeling （FDM） is one of the most popuIar additive manufacturing technologies for various engineering applications. FDM process has been introduced commercially in early 1990s by Stratasys Inc., USA. The quality of FDM processed parts mainly depends on careful selection of process variables. Thus, identifica- tion of the FDM process parameters that significantly affect the quality of FDM processed parts is important. In recent years, researchers have explored a number of ways to improve the mechanical properties and part quality using various experimental design techniques and concepts. This article aims to review the research carried out so far in determining and optimizing the process parameters of the FDM process. Several statistical designs of experiments and optimization techniques used for the determination of optimum process parameters have been examined. The trends for future FDM research in this area are described.