Microstructure and Mechanical Properties of AlSiTiCrNiCu Particles Reinforced Al6061 Composites by SPS and HPS Process

Three groups of AlSiTiCrNiCu high entropy alloy(HEA)particles reinforced Al606l composites were fabricated by spark plasma sintering at 520 and 570℃(S520,S570)and by hot-pressed sintering at 570℃(H570).The AlSiTiCrNiCu(AST)particles used as reinforcements were synthesized by mechanical alloying.The influences of the sintering process on the microstructure and mechanical properties of composites were investigated.The results showed that the AST particles had a near-equiatomic composition with a single BCC structure.The sintering temperature and time had a coupling influence on the interfacial microstructure.S520 had hardly reaction products and slight interfacial diffusion,and the AST particles were completely high entropy.Intense interfacial reactions happened on S570 and H570 with the same reaction products.The element diffusion of S570 was focused on the edge of the AST particles with partial loss of high entropy.Complete element diffusion and entire loss of high entropy of AST particles happened on H570.The differences in the microstructure caused by the three preparation methods led to the changes in mechanical properties and fracture mechanisms of composites.

A physically-based representative stress methodology for predicting stress rupture life of Ni-based DS superalloy

Smooth and three types of U-shape single-edge notched plate specimens adopted to experimentally investigate stress rupture behavior of Ni-based Directionally Solidified(DS)superalloy at 850℃ exhibit notch weakening effect and multi-source cracking initiation near the notch root.However,stress rupture behavior of smooth and V-shape notched round bars at 1040℃ revealed by Li et al indicates notch strengthening effect and creep micro-holes originating mostly from the central portion.A combined creep-viscoplastic constitutive model is employed to analyze the distribution of stress,strain and stress Triaxial Factor(TF)near the notch root.The different stress distribution and creep restraint between asymmetric notched plate specimens and symmetric notched round bars are the main reasons for the corresponding failure mechanism.Meanwhile,a good qualitative relationship exists between TF value and stress rupture life of notched specimen.Especially,the area with maximum TF value(TF_(max))is highly consistent with creep damage initiation region.Hence,based on the distribution characteristics of the initial tensile loading,a representative stress method independent of time-changing creep load at the location of TF_(max) is conducted for life prediction.The predicted results of both smooth and notched plate specimens and round bars agrees well with the experimental results.

Construction of digital 3D magic-cube organization structure for innovation-driven manufacturing

Owing to the heterogeneity between functional units and resource scarcity,manufacturing firms have been struggling with intra-organizational coordination for productivity and innovation.Traditional organizational structures,such as linear-functional and matrix,may cause responsibility division and independent goals(Shahani,2020),and are more difficult to be adopted by large-sized innovative manufacturing firms for quantity production.This is based on a review of several new forms of organization(i.e.,network organization,multiteam system,and platform organization)compared with the traditional forms of organization(i.e.,linear,matrix,and business unit organization,among others).This study proposes a three-dimensional(3D)magic-cube organizational structure,considering the product dimensions,business,and administration.Moreover,the characteristics,propositions of system operation,system dynamic model,and working model of the 3D magic-cube organization are described.Finally,the 3D model is applied in a Chinese manufacturing firm to test its effectiveness.By redesigning the post and pay system,the pilot organization establishes a project-driven and cross-functional coordination mechanism,positively affecting the firm’s financial profit,output value,labor productivity,and income of per capita.The proposed 3D model can be adopted by large-or medium-sized manufacturing firms for product development and innovation.The implications of both practice and theory are also discussed in this study.