High-Strength Aluminum LPBF with Ultrafast Laser Shock Forging
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Solution Overview
Problem
High-strength aluminum alloys are prone to thermal cracks and pores during laser powder bed fusion (LPBF) due to high temperature gradients and rapid cooling, affecting mechanical properties, and existing methods like in-situ alloying or thermal treatment introduce impurities or are difficult to control.
Innovation Solution
An ultrafast laser shock forging assisted LPBF method using nanosecond and ultrafast lasers with controlled parameters and a monitoring system to inhibit thermal cracks, avoiding alloying elements and post-treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional LPBF process is used for high-strength aluminum alloy, then manufacturing capability is achieved, but thermal cracks and pores are generated due to high temperature gradient and rapid cooling
Solution Approach 1:
The patent applies preliminary action by performing pre-heating treatment on the aluminum alloy before the main LPBF manufacturing process. This pre-heating step raises the base temperature of the substrate and powder bed, which suppresses the formation of thermal cracks and pores during subsequent rapid melting and solidification, while still enabling high-speed manufacturing
Solution Approach 2:
The patent changes the temperature parameter by introducing a pre-heating stage that raises the initial temperature before manufacturing. This parameter modification (increasing base temperature) fundamentally alters the thermal gradient profile, reducing excessive temperature differences during solidification and eliminating thermal cracks without sacrificing manufacturing productivity
2Reliability
If in-situ alloying method is used to narrow solidification temperature range, then thermal cracks are inhibited, but impurities are introduced that affect mechanical properties
Solution Approach 1:
The patent extracts the harmful alloying elements from the system by rejecting the in-situ alloying approach. Instead of adding elements like zirconium to modify solidification behavior, the patent uses pre-heating as a physical method to control temperature gradients, thereby avoiding impurity introduction while still achieving thermal crack inhibition
Solution Approach 2:
The patent converts the harmful effect of high temperature gradients (which cause cracks) into a beneficial controlled thermal field through pre-heating. By deliberately raising the base temperature before manufacturing, the excessive temperature gradients during solidification are reduced, transforming a harmful thermal condition into a controlled process parameter that prevents cracking without adding impurities
3Reliability
If heat treatment process is adopted to inhibit thermal cracks, then crack formation is reduced, but temperature control is difficult and secondary deformation occurs
Solution Approach 1:
The patent applies preliminary action by performing pre-heating treatment on the aluminum alloy before the main LPBF manufacturing process. This pre-heating step raises the base temperature of the substrate and powder bed, which suppresses the formation of thermal cracks and pores during subsequent rapid melting and solidification, while still enabling high-speed manufacturing
Solution Approach 2:
The patent skips the complex multi-stage heat treatment process by using a single pre-heating step before manufacturing. This streamlined approach avoids the temperature control difficulties and secondary deformation problems associated with post-manufacturing heat treatment, while still achieving effective thermal crack inhibition
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively controls stress fields to inhibit thermal cracks, ensuring high-quality aluminum alloy components with excellent performance without additional elements or treatments.
Implementation Method 1
melting the powder by the scanning galvanometer used for nanosecond laser
Implementation Method 2
melting the powder by the scanning galvanometer used for nanosecond laser, and after the powder melt is solidified rapidly
Implementation Method 3
allowing shock forging by the scanning galvanometer used for ultrafast laser
Implementation Method 4
an ultrafast laser shock forging assisted LPBF method
Data Source
AI summary
Provided is an ultrafast laser shock forging assisted laser powder bed fusion (LPBF) method capable of inhibiting formation of thermal cracks in a high-strength aluminum alloy. Technical points of the present disclosure: During a LPBF process of an aluminum alloy, a molten layer is subjected to shock forging with a mechanical effect of ultra-high-pressure shock waves induced by an ultrafast laser to reduce a stress level of the molten layer, and a stress level is controlled layer by layer to eliminate the local stress concentration, thereby inhibiting the formation of thermal cracks. Advantages of the present disclosure: During a LPBF-based additive manufacturing process, a stress field is controlled to inhibit the formation of thermal cracks, and there is no need to add an alloying element or adopt a post-treatment, resulting in a simple and reliable process. A thermal crack density is accurately and efficiently controlled layer by layer.