Hardness Mapping at Fold Lines: Quantifying Work Hardening
折缝硬度测绘：加工硬化的量化研究
标签：硬度测绘, 加工硬化, 折缝, 材料科学
用显微维氏硬度沿折缝横截面逐点测绘，可把折叠成型的经验规律量化：0.9 mm 紫铜一次 90° 折后，折缝根部硬度从 HV 65 升至 HV 130–150，影响带宽约 2–3 mm；第二次折叠加硬化 15–20%，第三次后趋于饱和，继续折叠即进入裂纹敏感区。硬度峰值带与实际开裂位置的吻合率超过 80%。实践结论：第三次折叠前必须退火；含锌黄铜硬化更快，退火间隔应减半。该测绘流程也适合作为进阶教学中的量化作业。
Mapping microhardness point by point across a fold cross-section quantifies fold-forming lore: one 90° fold in 0.9 mm copper raises the crease root from HV 65 to HV 130–150 with a 2–3 mm affected band; a second fold adds 15–20%, and by the third the hardening saturates—folding further enters the crack-sensitive zone. The hardness peak band matches observed cracking in over 80% of cases. Practical rules: anneal before the third fold, and halve the interval for zinc-bearing brasses, which harden faster. The mapping doubles well as a quantitative exercise in advanced teaching.