Material removal operations play a pivotal role in the manufacture of key components, required for engineering systems to operate safely and efficiently under ever more advanced functional requirements and over extended life cycles. To further step up the loading capability of machined parts, fundamental understanding of how of machining-induced features can influence the performance of advanced materials under complex service conditions is necessary over finer temporal and spatial scales. As discussed in Part I of this review, when engineering surfaces are generated by material removal processes, a wide range of physical mechanisms (e.g. mechanical, thermal, chemical and their combinations) drive the characteristics of workpiece surface integrity. In Part II of this review, the interplay between the metallurgical and micro-mechanical condition induced by material removal processes and their in-service response will be thoroughly explored, by a critical analysis of the state-of-the-art in the field. Specifically, attention is focused on recent advances made towards the understanding of the mechanisms determining the resistance of machined surface to fatigue crack nucleation (Section 2), corrosion and stress-corrosion cracking (Section 3), and wear (Section 4). Furthermore, the impact of relevant post-machining treatments on the in-service behaviour of machined surfaces is analysed, and the possible strategies for the enhancement of the functional performance of machined surfaces are presented (Section 5). Finally, the current research gaps and the prospective challenges in understanding the in-service behaviour of machined surfaces are critically discussed, providing an interpretation of the possible directions of future scientific development of this field.

Surface integrity in metal machining - Part II: Functional performance

被尝试答案作为产生的热用 200 W 纤维激光变硬和微观结构的精炼改进表面坚硬并且通过固体穿 AISI H13 工具钢的性质采购原料。激光的坚硬融化了地区被调查。为了识别热的效果，在融化地区的激光上输入，扫描条件被控制。结果显示出那，同样收到的 AISI H13 工具钢的坚硬是近似，在激光表面以后的 Hv 240，和坚硬加热处理在 Hv 480510 附近。变硬的深度和宽度随输入使用了的热的增加被增加。试验性的结果的申请将在 tooling 工业被考虑。

Laser surface hardening ofAISI H13 tool steel

Directed energy deposition (DED), also known as laser cladding, is one type of additive manufacturing where a high-power laser combined with a coaxial powder delivery system is used to produce metal components layer-by-layer. Despite many advancements in DED, little work has been accomplished in online estimation of mechanical properties, such as Young's modulus and Poisson's ratio, during the DED process. In this study, an online mechanical properties estimation technique was developed for the DED process using femtosecond laser ultrasonics and laser polishing. The unique contributions of this study are the following: (1) the development of a fully noncontact and nondestructive technique for the estimation of Young's modulus and Poisson's ratio using a femtosecond laser, (2) layer-by-layer estimation of mechanical properties accomplished by achieving micrometer-level spatial resolution, (3) laser ultrasonic measurement from a deposited metal layer using laser polishing instead of mechanical polishing, and (4) potential for online operation during the DED process. The performance of the proposed technique was examined using specimens fabricated under various DED operation conditions. The Young's modulus and Poisson's ratio values estimated by the proposed technique were consistent with those obtained from independent tensile tests performed after the completion of the DED process.

Mechanical properties estimation of additively manufactured metal components using femtosecond laser ultrasonics and laser polishing

Effects of icosahedral phase on mechanical anisotropy of as-extruded Mg-14Li (in wt%) based alloys

The study of corrosion behavior of manganese-based conversion coating on LZ91 magnesium alloy: Effect of addition of pyrophosphate and cerium

Influence of laser polishing on surface roughness and microstructural properties of the remelted surface boundary layer of tool steel H11

Effects of composition and growth rate on the microstructure transformation of β-rods/lamellae/α-rods in directionally solidified Mg-Li alloy

The invention discloses a preparation method for magnesium-lithium alloy with a regular structure. The method comprises the following steps that magnesium-lithium alloy with specific compositions is melted; molten magnesium-lithium alloy cast ingots are machined into bars through wire electrode cutting; the magnesium-lithium alloy bars are loaded; the loaded magnesium-lithium alloy bars are heated to the temperature required by directional solidification through a gradient heating method, and according to the gradient heating method, the magnesium-lithium alloy bars are heated to 500-700 DEG C and subjected to timing holding; the bars are heated to 750-950 DEG C and subjected to timing holding; the bars are heated to 1000-1100 DEG C and subjected to timing holding; and magnesium-lithium alloy heated to the temperature required by directional solidification is subjected to pull-down directional solidification.

Dan Liu

Papers

Influence of laser polishing on surface roughness and microstructural properties of the remelted surface boundary layer of tool steel H11

Effects of composition and growth rate on the microstructure transformation of β-rods/lamellae/α-rods in directionally solidified Mg-Li alloy

Preparation method for magnesium-lithium alloy with regular structure